Showing papers on "Adrenal cortex published in 1979"

Receptor-mediated uptake of lipoprotein-cholesterol and its utilization for steroid synthesis in the adrenal cortex

Abstract: Publisher Summary This chapter discusses the receptor-mediated uptake of lipoprotein cholesterol and its utilization for steroid synthesis in the adrenal cortex. It discusses the four model system (1)mouse adrenal tumor cells in culture (Y-1 clone) ,(2) rats treated in vivo with 4-aminopyrazolopyrimidine (4-APP), (3) bovine adrenal cortex ,and (4) Human fetal adrenal membranes to demonstrate the presence and physiological significance of low-density lipoprotein. The studies in the four model systems allow the formulation of a hypothetical working model to explain some aspects of cholesterol metabolism in the adrenal cortex. In this model, the adrenal is considered to have a small pool of metabolically active free cholesterol that is rapidly turning over. In the steady state, the input and output of cholesterol from this metabolically active cholesterol pool must be balanced. The net output of cholesterol from this pool occurs when cholesterol is converted to steroid hormones that are secreted from the gland and when cholesterol is esterified to form cholesteryl ester droplets. The adrenal gland contains at least two pools of cholesterol in addition to the metabolically active pool. One of these is a fixed pool of free cholesterol in cell membranes. The second pool of cholesterol is contained in storage droplets, where the cholesterol is esterified with fatty acids. These cholesteryl esters exert a buffer function that tends to stabilize the free cholesterol content of the adrenal gland during transient fluctuations in steroid demand. In the model systems, the endogenous synthesis of cholesterol in the adrenal is important in several situations: (1) when insufficient plasma lipoproteins are available, a situation that is probably never encountered in normal physiology, (2) transiently, when there is a sudden stimulus to steroid secretion and sufficient time has not elapsed for the full induction of lipoprotein receptor activity, and (3) when the rate of steroid synthesis is so great that maximal lipoprotein receptor activity cannot supply sufficient cholesterol and supplementary cholesterol synthesis within the gland is required.

Appearance of catecholamine-synthesizing enzymes during development of rat sympathetic nervous system: Possible role of tissue environment

Abstract: We sought to determine, in rat embryo, when and at what site in their migration cells derived from the neural crest differentiate into sympathetic neuroblasts. This has been accomplished by immunocytochemical detection, within the cells, of the enzymes catalyzing catecholamine biosynthesis—tyrosine hydroxylase [TH; tyrosine 3-monooxygenase, L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2] dopamine-β-hydroxylase [DBH; 3,4-dihydroxyphenylethylamine,ascorbate:oxygen oxidoreductase (β-hydroxylating), EC 1.14.17.1)]—and, as a marker of prospective adrenal medullary cells, the enzyme phenylethanolamine N-methyltransferase (PNMT; S-adenosyl-L-methionine:phenylethanolamine N-methyltransferase, EC 2.1.1.28). TH and DBH, not detected in the neural crest, appear almost simultaneously in cells of the thoracic sympathetic ganglia in 11-day-old embryos, and in abdominal and lumbar ganglia 1-2 days later, thereby exhibiting a characteristic rostral-caudal gradient of differentiation. Cells stained for TH and DBH are seen in the gut wall from day 11 to day 14, but not thereafter. Cells stained for TH and DBH appear in the adrenal anlage at day 15. However, PNMT is not detected in the adrenal until day 17 of development, and is present only in the sympathoblasts in contact with the adrenal cortex. Treatment of pregnant rats with dexamethasone failed to accelerate the appearance of PNMT in the embryo or to initiate its expression in cells of other sympathetic organs. We conclude that neural crest cells express a noradrenergic phenotype only after leaving the neural crest and that these cells are labile with respect to their neurotransmitter and are capable of transformation in response to environmental stimuli.

Corticotrophin releasing factor may be modulated vasopressin.

Abstract: CORTICOTROPHIN RELEASING FACTOR (CRF) was the first of the postulated hypothalamic factors controlling the release of hormones from the pituitary gland to be demonstrated biologically1. However, it is extraordinary that after 24 years of research, techniques which have established the identity of the hypothalamic peptides involved in the release of thryotrophin, the gonadotrophins and growth hormone, have been unsuccessful when applied to the search for a factor responsible for adrenocorticotrophin (ACTH) release2,3. Vasopressin invariably releases ACTH from the anterior pituitary, but its partial agonistic properties in vitro4–6, its low potency in vivo7 and the isolation of active CRF fractions with little or no vasopressin activity2,3,8,9 have led to its rejection as a physiological CRF10,11. However, recent immunological and immunocytochemical findings have led to renewed interest in the role of vasopressin in ACTH release. High concentrations of immunoreactive vasopressin have been found in portal blood and a direct vasopressin-neurophysin containing axonal pathway to the hypophyseal portal system, which seems to be under the influence of the adrenal cortex, has been identified12,13. Using a sensitive releasing factor bioassay system, the perfused isolated anterior pituitary cell column14, and various immunological techniques, we have presented evidence to support the idea that vasopressin plays a major part in control of ACTH release6, and we now report the existence of hypothalamic factors with weak, labile CRF activity which potentiate the CRF activity of vasopressin to give it full agonistic properties indistinguishable from crude extracts of rat stalk median eminence (SME). Thus we propose that CRF is vasopressin modulated by other hypothalamic factor(s) released into the hypothalamo-hypophyseal portal system.

Low density lipoprotein receptors in bovine adrenal cortex. II. Low density lipoprotein binding to membranes prepared from fresh tissue.

Abstract: Low density lipoprotein (LDL)-binding activity was measured in whole homogenates and membranes prepared from fresh bovine adrenal cortex by an ultracentrifugation assay. The binding site for 125I-labeled LDL in isolated membranes shared the properties of the LDL receptor previously demonstrated in intact monolayers of cultured bovine adrenocortical cells. The amount of high affinity [125I]iodo-LDL-binding activity in the adrenal cortex was 6- to 12-fold higher than in the medulla of the same glands. Large amounts of high affinity [125I]iodo-LDL-binding activity were also present in the ovarian corpus luteum but not in the ovarian interstitium. Lesser amounts of high affinity binding activity were observed in 14 other bovine tissues. These results lend support to the concept that cells in the bovine adrenal cortex can obtain cholesterol for steroid hormone synthesis through the receptor-mediated uptake of plasma LDL.

Influences of adrenocortical hormones on pituitary and brain function.

Abstract: Adrenocortical secretions influence neuroendocrine function and behavior, and it is possible to recognize separate physiologic actions of gluco- and mineralocorticoids. The search for neuroanatomical sites and cellular modes of adrenocorticoid action has revealed a system of putative glucocorticoid receptors in neurons of the hippocampus, septum, amygdala, and entorhinal cortex, and in the pituitary. No part of the brain is totally devoid of receptor activity, however, and glial cells may also contain glucocorticoid receptors. Mineralocorticoid receptors are less well characterized neuroanatomically or biochemically. One reason for this is the considerable degree to which both gluco- and mineralocorticoids bind to both classes of receptors in vitro. Another reason may be the overwhelming quantitative predominance of glucocorticoid over mineralocorticoid receptors in neural tissue. Glucocorticoid receptors of the pituitary, which have a high avidity for dexamethasone, appear to participate in the delayed negative feedback effects of glucocoticoids. Functional correlates of neural glucocorticoid receptors remain to be clearly established. Among the possibilities are several reported effects on hippocampal neural activity that have an onset latency of 20--30 min and a duration of several hours. The relative rapidity of such effects does not preclude genomic mediation, as genomic effects of glucocorticoids on thymus lymphocytes have been detected within as little as 15 min of steroid application [117]. What are not so far explained by the intracellular receptor mechanism are the extremely rapid effects of glucocorticoids such as the rate-sensitive negative feedback on CRF and ACTH secretion. These may involve a direct action of the steroid on cell membranes in the pituitary and hypothalamus.

Endocrine interaction of the thymus with the hypohysis, adrenals and testes: effects of two thymic extracts.

Abstract: The concentration of ACTH, corticosterone, LH and testosterone in the plasma of rats have been measured in normal, thymectomized and sham-operated rats. A group of rats, thymectomized at birth, received two i.p. injections weekly of two thymic extracts, each prepared in a separate way. Neonatal thymectomy was followed by the appearance of a transitory wasting disease during which a hormonal unbalance was manifest. Plasma corticosterone and ACTH levels increased at first at 30 days after thymectomy and then decreased at 60 days. The levels of the different hormones returned to normal by 90 days. The injections of thymic extracts rectified all these perturbations. The plasma levels of testosterone and corticosterone of hypophysectomized rats were compared to those of hypophysectomized and thymectomized animals. Results suggested that the thymus has a direct action of the adrenal cortex and in indirect action on the testes. The indirect effect is probably mediated through the hypophysis.

Acute Self-Suppression of Corticosteroidogenesis in Isolated Adrenocortical Cells

Abstract: The relation between steroidogenesis induced by ACTH and that induced by exogenous concentrations of glucocorticoids was studied in isolated adrenocortical cells. Exogenous corticosterone and cortisol, in concentrations within the production capacity of the adrenal gland, suppressed steroidogenesis induced by ACTH in rat and beef cells, respectively. The precursors pregnenolone and progesterone enhanced steroidogenesis in both rat and beef cells. Aldosterone in rat cells and 17 beta-estradiol in rat and beef cells had little if any effect on steroidogenesis. Either suppression or stimulation by exogenous steroids was acute, that is, after 2-h incubation for rat cells and 1-h incubation for beef cells. A direct suppressive action of end product glucocorticoids is indicated. This observed self-suppression of adrenocortical cells suggests the existence of a mechanism for the find adjustment of steroidogenesis that operates in addition to the classical control exerted by the anterior pituitary.

The role of serum lipoproteins in steroidogenesis by the human fetal adrenal cortex

Abstract: In the present investigation it was found that human fetal adrenal tissue maintained in organ culture secreted appreciable quantities of dehydroisoandrosterone sulfate (DS) and cortisol. Pregnenolone was also secreted in significant amounts, principally as the sulfate ester. The highest rate of secretion of these steroids by fetal adrenal tissue occurred when both ACTH and whole human serum were present in the culture medium. In the absence of ACTH, steroid secretion was low. When whole serum was replaced by lipoprotein-poor serum, the steroidogenic response to ACTH was markedly attenuated but not abolished. On the basis of these findings, it is concluded (1) that the human fetal adrenal can synthesize steroid hormones cte novo from cholesterol, (2) that ACTH is an important stimulant of steroidogenesis by the human fetal adrenal, and (3) that pTasma lipoproteins are a major source of the cholesterol utilized by the human fetal adrenal for steroidogenesis. Hence, it is likely that factors which regulate t...

The action of nicotine on the pituitary-adrenal cortical axis.

Abstract: Nicotine was found to raise dramatically plasma corticosterone levels in a dose-dependent manner. Plasma corticosterone time course for the 100 microgram/kg dose of nicotine produced an initial increase in corticosterone elevation which did not return towards control levels until after 30 min. The 200 and 500 microgram/kg doses, however, indicated a biphasic response for nicotine-induced steroid secretion. The first steroid peak occurred 1-15 min after nicotine administration and was followed by a greater elevation at 20 min. Plasma nicotine levels did not show the same biphasic pattern. The nicotine-induced plasma steroid elevation was completely abolished by hypophysectomy, indicating that the response to nicotine must be mediated through ACTH release from the anterior pituitary. The administration of exogenous ACTH to rats pretreated with betamethasone was found to result in a biphasic plasma steroid elevation similar to that seen after injection of 200 microgram/kg nicotine. It was postulated that this may reflect a differential response of the adrenal cortex to a single ACTH outflow.

Attenuation of Angiotensin II- and III-induced Aldosterone Release by Prostaglandin Synthesis Inhibitors

Abstract: The effect of two prostaglandin synthesis inhibitors, indomethacin and meclofenamate, on angiotensin II (AII)- and III (AIII)-induced aldosterone release was studied in normal and sodium-depleted conscious rats and in adrenal capsular cell suspensions obtained from normal rats. In normal rats, in vivo AII and AIII were equipotent in causing dose-related increases in serum aldosterone concentrations. Indomethacin decreased the basal serum aldosterone levels by 50% and serum renin levels by 43%. In addition, the steroidogenic effects of AII and AIII were reduced by 45 and 63% with 3 mg/kg of indomethacin and 63 and 73% with 10 mg/kg, respectively. In contrast, meclofenamate failed to alter basal serum levels of aldosterone or AII-stimulated aldosterone release but inhibited serum renin levels by 27% and the aldosterone-stimulating effect of AIII by 99%. Indomethacin (3 mg/kg) and meclofenamate (2 mg/kg) inhibited urinary prostaglandin (PG)E(2) and PGF(2alpha) excretion by 63 and 52% and 37 and 31%, respectively. Both inhibitors significantly decreased the adrenal capsular PGE(2) and PGF(2alpha) content and the conversion of [(14)C]arachidonate to [(14)C]PGE(2) and [(14)C]PGF(2alpha). In sodium-depleted rats, indomethacin produced similar effects reducing the control serum aldosterone levels by 29%, AII-stimulated aldosterone by 47%, and completely suppressing the aldosterone response to AIII without altering serum renin activity. In adrenal cell suspensions, similar results were observed with indomethacin inhibiting basal and AII- and AIII-stimulated aldosterone release by 29, 81, and 93%, respectively. Meclofenamate failed to alter basal and AII-stimulated aldosterone release but inhibited that stimulated by AIII by 86%. The present findings suggest that prostaglandins modulate the effects of the renin-angiotensin system by stimulating the release of renin from the kidney and augmenting the steroidogenic effects of AII and AIII in the adrenal cortex.

Mediatory role of calcium and guanosine 3', 5'-monophosphate in adrenocorticotropin-induced steroidogenesis by adrenal cells

Abstract: When incubated in a calcium-free medium, isolated rat fasciculata cells showed neither an increase in the concentration of guanocine 3',5'-monophosphate (cyclic GMP) nor an increase in corticosterone production in response to adrenocorticotropic hormone (ACTH). In response to submaximum and maximum steroidogenic concentrations of ACTH, corticosterone formation was directly proportional to increases in calcium concentration ranging from 0 to 2.5 mM. Higher concentration of calcium, however, inhibited maximal ACTH-induced steroidogenesis. In the absence of ACTH, calcium did not stimulate cyclic GMP accumulation and corticosterone formation. ACTH-induced corticosterone synthesis, preceded by an increase in cyclic GMP, was restored when ACTH and calcium were both present in the medium. Cyclic GMP or dibutryl cyclic GMP-induced steroidogenesis was substantially reduced in the absence of calcium, but in contrast to the ACTH effect a significant amount of corticosterone formation occurred without calcium. It is proposed that at the physiological concentrations of the hormone, calcium regulates the transduction of information between hormone receptors and guanylate cyclase.

Stimulation of Pituitary-Adrenocortical System by Ginseng Saponin

Abstract: Effects of preparations of saponin mixture and isolated ginsenosides, extracted from the root of Panax ginseng, on plasma corticotropin (ACTH) and corticosterone concentrations in rats were determined by the radioimmunoassay and competitive protein binding method. When ginseng saponin mixture was administered to rats intraperitoneally, plasma ACTH and corticosterone increased significantly 30, 60 and 90 min after the treatment. The kinetic pattern of the increase in plasma ACTH was almost parallel to that in plasma corticosterone. Isolated ginsenoside, protopanaxadiol or protopanaxatriol glycoside, also increased plasma corticosterone. The ginseng-induced increase in plasma corticosterone was suppressed by pretreatment with dexamethasone. Thus the ginseng saponin was found to act on the hypothalamus and/or hypophysis primarily, and stimulated ACTH secretion which resulted in increased synthesis of corticosterone in the adrenal cortex.

Stereospecific opiate binding in bovine adrenal medulla.

Abstract: In this report we describe a population of high affinity, saturable, opiate binding sites in the adrenal medulla. These sites show the typical sensitivity to sodium ions characteristic of opiate binding sites found in brain tissue. No comparable high affinity sites were detectable in adrenal cortex.

Calcium Ion as “Second Messenger” in Corticoidogenic Action of ACTH

Abstract: The correlation between corticoidogenesis and Ca2+-influx in the cell was investigated using isolated rat or bovine adrenocortical cells. 1) ACTH-induced corticoidogenesis in both rat and bovine adrenocortical cells was enhanced in parallel with increasing concentration of external Ca2+. In the bovine cells but not in the rat cells, moreover, the marked stimulatory effect of external Ca2+ on the corticoidogenesis was observed despite the absence of ACTH. 2) Ca2+-influx and corticoidogenesis always occurred unitedly. 3) Verapamil markedly inhibited either corticoidogenesis or Ca2+-influx in response to ACTH. 4) The stimulatory effect of Ca2+ on corticoidogenesis was completely blocked by cycloheximide. It was therefore suggested that Ca2+ could regulate corticoidogenesis as a primary "second messenger" of ACTH through biosynthesis of so-called steroidogenic protein.

Regulation of Deoxyribonucleic Acid Synthesis in Bovine Adrenocortical Cells in Culture

Abstract: . Factors which regulate proliferation of adrenocortical cells have been investigated using mass cultures and clones of bovine cells. Fibroblast growth factor (FGF) and angiotensin II are the most potent mitogens identified for bovine adrenocortical cells; FGF exerts greater effects than angiotensin II. FGF and angiotensin II not only stimulate [3H]thymidine incorporation into DNA and the rate of cell proliferation but also increase the saturation density achieved. Although equivalent saturation densities occur with angiotensin II and FGF, cell overlapping occurs with FGF but not with angiotensin II. Insulin, multiplication stimulating activity, and somatomedin C are weak mitogens, increasing [3H]thymidine incorporation in DNA 2- to 3-fold when added at high concentrations. These agents potentiate FGF and angiotensin II mitogenic effects. Thrombin has weak stimulatory effects on DNA synthesis which are additive to those of FGF or angiotensin II. The interaction between angiotensin II and FGF was v...

Electrical responses in cat adrenal cortex: possible relation to aldosterone secretion.

Abstract: The effects of secretagogues for aldosterone release were studied on the membrane potential of cells in the adrenal cortex of the cat. Adrenal glands were excised, sliced, and continuously superfused. Membrane potentials were recorded from both zona glomerulosa and zona fasciculata-reticularis. Secretagogues, angiotensin II (1 microgram/ml) and 20 mM KCl, were found to depolarize cells rapidly. Ouabain (10(-5) M) also depolarized the membrane potential although the response was sluggish. Samples of the superfusate were collected and analyzed by radioimmunoassay for their aldosterone and cortisol content. Depolarizing concentrations of angiotensin II, KCl, and ouabain seemed to increase aldosterone release. Cortisol output was more variable. Saralasin blocked the effects of angiotensin II on the membrane potential. These experiments suggest that membrane depolarization plays a role in the stimulus-secretion coupling of mineral corticoids.

Direct Inhibitory Effect of Dexamethasone on Steroidogenesis of Human Adrenal in Vivo

Abstract: A rapid ACTH test was used to investigate the direct effect of glucocorticoid on the steroidogenesis by the adrenal cortex in man. The plasma cortisol response to 250 μg iv synthetic a-ACTH-(l–24) (Cortrosyn) was determined in normal subjects pretreated with 2 and 12 mg dexamethasone. The 15- and 30-min increments in plasma cortisol levels in response to ACTH injection after pretreatment with 12 mg dexamethasone were significantly suppressed compared to values obtained after pretreatment with 2 mg dexamethasone. The present study suggests that there is a direct inhibitory effect of glucocorticoid on adrenocortical steroidogenesis in man.

Abnormal adrenal responsiveness and angiotensin II dependency in high renin essential hypertension.

Abstract: Adrenal responsiveness to angiotensin II (AII) and the diastolic blood pressure responses to saralasin were studied in 19 patients with high renin essential hypertension (HREH) on a 10-meq Na(+)/100 meq K(+) diet. The increment in plasma renin activity (PRA) between supine and upright positions was used as an estimate of the acute stimulation of the adrenal gland by endogenous AII; the normal increment in plasma aldosterone divided by the increment in PRA was >3.8. 7 of 19 had abnormal upright posture responses with significantly greater mean PRA increments (24+/-6 ng/ml per h) and significantly smaller plasma aldosterone increments 47 +/- 16 ng/dl) (P < 0.036) compared to the increments observed in HREH patients with normal adrenal responsiveness (PRA = 15 +/- 1 ng/ml per h; plasma aldosterone = 87 +/- 17 ng/dl). When AII was infused at doses of 0.1-3 ng/kg per min, only patients with normal posture responses had normal plasma aldosterone increments; plasma aldosterone levels failed to significantly increase even at the highest infusion rate in the patients with the abnormal upright posture responses. The AII competitive inhibitor, saralasin (0.3-30 mug/kg per min) was then infused to study the occurrence of angiotensinogenic hypertension in both HREH subgroups. The mean decline in diastolic blood pressure to saralasin in the subnormal adrenal responsive patients (-15 +/- 3 mm Hg) was significantly greater than in the normal adrenal responsive group (-3 +/- 2 mm Hg) (P < 0.02).It is concluded that patients with HREH are not a homogeneous population; approximately one-third have AII-dependent hypertension. In these patients, the mechanism responsible for the elevated renin and blood pressure could be a compensatory increase secondary to decreased adrenal responsiveness to AII. In the remainder, the high PRA levels have little, if any, causal role in the pathogenesis of the hypertension but could reflect a marker of other pathophysiologic processes.

Increase in free cholesterol content of the adrenal cortex after stress: Radioautographic and biochemical study

Abstract: The purpose of this investigation was to quantify free cholesterol biochemically and in radioautographs of 3H-digitonin cholesterol complex in fasciculata cells of control and stressed rat adrenal cortex. Stress was induced by ether, laparotomy, and adrenal and intestinal handling. Control rats were anesthetized with nembutal. All animals were killed ten minutes from the beginning of anesthesia. The adrenals were excised and either fixed in glutaraldehyde containing 3H-digitonin or homogenized for biochemical determination of free cholesterol. The plasma corticosterone level of each animal was measured. The fixed adrenals were processed, using different methods of dehydration and embedment, for light and electron microscopic radioautography. The mean number of silver grains (mean) per unit area of zona fasciculata was counted from light microscopic radioautographs. Crystals of cholesterol-digitonide complex were more numerous in stressed fasciculata cells, particularly over SER. Silver grains were localized over or close to the crystals. The mean for stressed rats was significantly higher than control values, indicating more free cholesterol in fasiculata cells of stressed rats. The results were not affected by either the method of dehydration or the type of embedding medium used. The morphologic results were substantiated by biochemical findings of increase in free cholesterol in adrenals of stressed rats. Plasma corticosterone was significantly high in stressed rats. The increase in free cholesterol in stimulated fasciculata cells is consistent with a previously reported increase in cholesterol esterase activity after ACTH stimulation.

Different biological action of corticosteroids, corticosterone and cortisol, as a base of zonal function of adrenal cortex

Abstract: The effects of corticosterone and cortisol in concentrations attainable in the adrenal gland were studied on ACTH-induced steroidogenesis in cultured cortical cells of foetal human and rat adrenals. Corticosterone at a concentration of 5.8 x 10(-5) mol/l clearly inhibited cortisol production (65.5%; P less than 0.005) and simultaneously increased androgen production in tissue culture of foetal human adrenals. Cortisol at a concentration of 2.8 x 10(-4) mol/l clearly inhibited 18-OH-DOC (74.0%, P less than 0.001) and aldosterone (83.7% P less than 0.005) production in tissue culture of foetal rat adrenals. In primary culture of foetal human adrenals cortisol did not decrease aldosterone production absolutely, but it significantly decreased the relative amount of aldosterone with respect to corticosterone. Cortisol did not inhibit corticosterone production in either culture. The results demonstrate that cortisol and corticosterone have qualitatively different effects on adrenal steroidogenesis and that these steroids may play a basic role in the functional zonation of the adrenal gland.

Microsomal aryl hydrocarbon hydroxylase in rat adrenal: regulation by ACTH but not by polycyclic hydrocarbons.

Abstract: Whereas total P-450 content is more than four times greater in the rat adrenal cortex mitochondria than in microsomes, aryl hydrocarbon (benzo[a]pyrene) hydroxylase (EC 1.14.14.2) activity is more than 60 times higher in adrenal cortex microsomes than in mitochondria. The rat adrenal microsomal hydroxylase activity is strongly inhibited by α-naphthoflavone in vitro ; progesterone 21-hydroxylase is not. In rats hypophysectomized for 30 days, aryl hydrocarbon hydroxylase decreases to about 6% of control values, but progesterone 21-hydroxylase falls to about 38% of that in sham-operated control animals. Hypophysectomy causes a striking decrease in an ebectrophoretic band estimated to be about 57,000 daltons. Aryl hydrocarbon hydroxylase specific activity and this electrophoretic band are restored to normal levels in adrenal microsomes of hypophysectomized rats that have received exogenous ACTH treatment. Aryl hydrocarbon hydroxylase in adrenal microsomes is not induced, however, in the hypophysectomized or intact rat by 3-methylcholanthrene or high doses of 2,3,7,8-tetrachlorodibenzo- p -dioxin. These data show that aryl hydrocarbon hydroxybase and progesterone 21-hydroxylase may be associated with different forms of adrenal microsomal P-450. It is of interest that aryl hydrocarbon hydroxylase in the adrenal of the untreated rat is similar (in sensitivity to α-naphthoflavone and in the presumed association with the 57,000-dalton apoprotein subunit on electrophoresis) to polycyclic aromatic compound-induced aryl hydrocarbon hydroxylase and its associated cytochrome P 1 -450 in rat liver. The regulation of the adrenal hydroxylase by the large polypeptide hormone ACTH and the lack of inducibility by polycycic aromatic compounds, however, are characteristics distinctly different from those of the P 1 -450-associated hepatic enzyme.

Studies on cyclic nucleotides in the adrenal gland

Abstract: Effects of ACTH and calcium on cyclic AMP and steroid production by the zona fasciculata-reticularis (the decapsulated fraction) from the rat adrenal cortex have been studied. Increasing concentrations of extracellular calcium enhanced the action of ACTH on cyclic AMP and steroid production. These effects of ACTH with calcium were prevented by lanthanum, but not by tetracaine or verapamil, suggesting that ACTH stimulation may be mediated by calcium through a process not involving the tetracaine- or verapamil-vulnerable step(s) of the calcium current. High concentrations of external calcium itself increased cyclic AMP accumulation without any increase in steroidogenesis. A calcium ionophore, X537A was stimulatory for steroidogenesis but inhibitory with respect to cyclic AMP accumulation. Considered together with the findings of AMP increase, these results suggest that ACTH primarily increases intracellular calcium mobilization thus stimulating directly the steroidogenesis, which is independent of the cyclic AMP system. Relatively high concentrations of ACTH activate the adenylate cyclase, which depends on extracellular calcium to increase cyclic AMP levels and stimulation of steroidogenesis by the decapsulated fractions of the adrenal cortex.

Immunohistochemical localization of adrenodoxin and adrenodoxin reductase in bovine adrenal cortex

Abstract: The zonal distribution of adrenodoxin and adrenodoxin reductase (EC 1.6.7.1) in the bovine adrenal cortex as well as their intracellular localization has been studied by the direct method of peroxidase-labelled antibody (Fab' or F(ab')2 fraction) technique. The results indicated that both proteins localized mainly in zonae fasciculata and reticularis whereas very few were present in the zona glomerulosa. Only parenchymal cells in the adrenal cortex were proved to contain both proteins. The intracellular localization of both adrenodoxin and the reductase was demonstrated to be exclusively on the inner membrane of mitochondria of these parenchymal cells by immunoelectron microscopy. The validity of the immunocytochemical method employed in this study to determine the fine localization of both proteins in the mitochondria as well as the significance of the zonal distribution in relation to the function of each individual zone is discussed.