Showing papers on "Adrenal cortex published in 1976"

Angiotensin-converting enzyme: vascular endothelial localization

Abstract: Fluorescein-labeled antibody to rabbit pulmonary angiotensin-converting enzyme localized in the vascular endothelium of rabbit lung, liver, adrenal cortex, pancreas, kidney, and spleen. Epithelial cells of the renal proximal tubules were the only parenchymal cells among the organs studied that demonstrated immunoreactivity.

Regulation of angiotensin II receptors in the rat adrenal cortex by dietary electrolytes.

Abstract: The binding affinity and concentration of specific angiotensin II receptor sites of rat adrenal cortical cells and homogenates were determined after 1 and 6 wk of altered sodium and potassium intake. Sodium deprivation caused marked increases in plasma renin, blood angiotensin II, and plasma aldosterone, and was accompanied by a significant increase (+74%) in the number of specific angiotensin II receptor sites per adrenal cortical cell. High potassium intake was followed by increased serum potassium and markedly elevated plasma aldosterone, with subnormal levels of renin and angiotensin II and a 170% increase in the number of angiotensin II receptors per cell after 1 wk. Sodium loading and potassium deprivation were followed by the opposite effect upon adrenal receptors, with reduction of the angiotensin II-binding capacity. None of the dietary electrolyte changes were accompanied by an ancrease in receptor affinity above the control value of 2 nM-1. A decrease in receptor affinity was noted after 6 wk of either low sodium or low potassium intake, when the renin and angiotensin II levels were increased by 104-129%. The adrenals of normal rats infused acutely with synthetic angiotensin II, or anesthetized with ether or sodium pentobarbital, which markedly increased plasma renin activity, contained fewer angiotensin receptors. These reductions in binding site concentration were not accompanied by changes in affinity and were attributed to occupancy by angiotensin II. These studies have demonstrated that chronic changes in sodium or potassium balance and acute changes in blood angiotensin II levels can exert modulating effects upon the adrenal content and/or affinity of specific receptor sites for angiotensin II.

Subcellualr distribution of protein carboxymethylase and its endogenous substrates in the adrenal medulla: possible role in excitation-secretion coupling.

Abstract: Protein carboxymethylase (S-adenosyl-L-methionine:protein O-methyltransferase, EC 2.1.1.24) transfers a methyl group from S-adenoxyl-L-methionine to carboxyl side chains of proteins to form labile protein-methyl esters which, thus, neutralize negative charges. This enzyme was examined for its possible participation in excitation-secretion coupling in the adrenal medulla. Protein carboxymethylase has a specific activity several times higher in the adrenal medulla than in the adrenal cortex; also, the medulla has a higher concentration of methyl-acceptor proteins. In the adrenal medulla, 97% of the enzyme was localized in the cytosol. Of the various subcellular fractions of the medulla, the catecholamine-containing chromaffin vesicles had the highest concentrations of substrat(s) for protein carboxymethylase. Carboxymethylation of proteins in intact chromaffin vesicles results in stripping of methylated protein(s) from the membranes. Thus, protein carboxymethylase appears to be involved in the neutralization of charges on the surface of chromaffin vesicles and in the release of surface proteins; both phenomena are likely to be required for exocytosis.

Endocrinopathy in thalassaemia major.

Abstract: Pituitary, adrenal, and pancreatic functions were investigated in 9 patients with thalassaemia major. 9 a.m. plasma ACTH values were 148-480 pg/ml (normal range 15-70 pg/ml). Cortisol and growth hormone response to insulin-induced hypoglycaemia was normal in all. 24-hour urinary excretions of 17-ketosteroids and 17-hydroxycorticosteroids were normal. There was normal cortisol response to intramuscular injection of ACTH. In a physiological adrenal stimulation test there was a significantly smaller response to each physiological dose of tetracosactrin. 4 patients had diabetic glucose tolerance tests--none are clinically diabetic. The mean plasma glucose utilization constant (Kgl=2-02) is significantly smaller than normal. Plasma insulin response both in the oral and the intravenous glucose tolerance test was significantly smaller than normal. The data were consistent with severe and widespread impairment of endocrine function and a plausible explanation would be iron deposition in endocrine organs. It is suggested that pituitary hyperfunction of ACTH secretion is due to target organ unresponsiveness which can be shown in its early stages only by a physiological test of the adrenal cortex. Skin pigmentation in thalassaemia seems to be due to the melanophore-stimulating effect of this raised plasma ACTH.

Effects of spironolactone, canrenone and canrenoate-K on cytochrome P450, and 11beta- and 18-hydroxylation in bovine and human adrenal cortical mitochondria.

Abstract: Effects of spironolactone, canrenone and canrenoate-K on adrenal cytochrome P450 (P450) and corticosteroid biosynthesis were examined by studying difference spectra, P450 reduction and corticoid hydroxylation in mitochondrial preparations isolated from zona fasciculata and zona glomerulosa of bovine adrenals and from adrenal adenoma and hyperplastic adrenal cortex removed from patients with hyperaldosteronism. All three agents bound to P450 producing type I difference spectra and underwent hydroxylation. They all inhibited 11beta-hydroxylation in bovine adrenal at 30 muM and higher concentrations. Canrenone, the most potent inhibitor, blocked enzyme activity by 60% at a concentration of 60 muM. Spironolactone stimulated P450 reduction. The order of potency of inhibition was found to correlate with the order of affinity of these agents for P450. 11beta-Hydroxylase in human adrenal appeared to be less sensitive to canrenone. All three agents or their hydroxylated metabolites blocked 18-hydroxylation in bovine adrenal at lower concentrations. Canrenoate-K, being the most effective, inhibited 52% at 20 muM. Low concentrations of canrenone (2.5-5.0 muM) were without effect on 11beta-hydroxylase but markedly inhibited 18-hydroxylation (62-76%) in hyperplastic human adrenals. The inhibitors produced mixed type inhibition of 11beta-hydroxylation and competitive type inhibition of 18-hydroxylation. These findings indicate that at low concentrations spironolactone and its major metabolites, canrenone and canrenoate-K, or their hydroxylated metabolites, can directly interfere with the biosynthesis of aldosterone in bovine and certain human adrenal cortical tissue.

Steroid formation and differentiation of cortical cells in tissue culture of human fetal adrenals in the presence and absence of ACTH.

Abstract: Steroid secretion and ultrastructural differentiation of human fetal adrenal cortical cells were analyzed in tissue culture with and without ACTH. The unconjugated and sulfated endogenous neutral steroids were analyzed by gas-liquid chromatography and gas chromatography-mass spectrometry. A fetal pattern of neutral steroids, including high concentrations of sulfate conjugates, was found during the first five days of the cultivation. At 6 to 11 days of cultivation, a decrease was seen in concentrations of these steroids. However, when stimulated with ACTH, an increasing amount of steroids was secreted during days 6 to 11 and their pattern was transformed into the adult type with a 30-200 times higher secretion rate of cortisol. Cortical cells capable of proliferation in the culture had the ultrastructure of the permanent zone cells of the fetal adrenal or adult zona glomerulosa type. ACTH stimulation induced a differentiation of these cells into zona fasciculata type. The results suggest that ACTH is the m...

Adrenocortical factors in hypertension. I. Significance of 18-hydroxy-11-deoxycorticosterone.

Abstract: Low renin essential hypertension and the syndrome of mineralocorticoid excess have two features in common, low plasma renin activity and volume-sensitive hypertension. The proposal that both disorders share a common mechanism--because of the ability of agents that inhibit or antagonize the adrenocortical secretion to lower blood pressure in the low renin hypertensive group--appears to be based on a circular argument. The beneficial effect of removal or neutralization of the adrenocortical contribution only constitutes evidence for volume-dependency or sensitivity, which is how the low renin group is defined. Any measure that blocks a component of the normal homeostatic chain for the maintenance of extracellular and intravascular volume including the adrenal cortex would be expected to have a beneficial effect in volume-sensitive hypertension. Evidence for an adrenal factor in low renin hypertension must rest on the isolation of an active substance that reproduces the effect when readministered. 18-Hydroxy-11-deoxycorticosterone (18-OH-DOC) does not meet these criteria. It is not significantly increased in experimental hypertension and, although its overproduction in unselected low renin essential hypertensive patients remains controversial, the magnitude of the reported elevations is insufficient in relation to the low biologic activity of the steroid to account for a significant effect. Apart from its increase in the 17alpha-hydroxylase defect, 18-OH-DOC is increased in primary aldosteronism and may also be an indicator of a histologic variant of the aldosteronoma. On the basis of a large body of evidence showing parallelism between the 11beta- and 18-hydroxylase functions of the fasciculata zone, we have proposed that both enzymic functions are functionally related and may involve the same enzyme protein and catalytic site. According to this view, the secretion of 18-OH-DOC would have no special significance of its own but would be an obligatory consequence of the secretion of fasciculata zone corticosterone.

Evidence that des-Asp1 angiotensin II mediates the renin-angiotensin response.

Abstract: Studies were undertaken to compare and evaluate the influence of angiotensin II and its heptapeptide fragments, des-Asp-1-angiotensin II, at various receptor sites for angiotensin in both dogs and rats. Receptor sites evaluated were those which are found in the glomerulosa, reticularis, and fasiculata of the adrenal cortex, in the renal arterioles and the juxtaglomerular cells of the kidney, and in the peripheral arterioles. Both peptides produced similar changes in the steriod secretion profiles for aldosterones, corticosterone, and cortisol in the dog. In the rat, both peptides similarly increased aldosterone and corticosterone secretion; however, a larger dose of the competitive antagonist Sar-1,Ala-8-angiotensin II was required to block the steroid response to the heptapeptide. This finding suggests that receptor affinity for des-Asp-1-angiotensin II may be greater than its affinity for angiotensin II. Both peptides also decreased renin secretion and renal blood flow similarly in the dog. The pressor response to the heptapeptide was only about one-half the pressor response to angiotensin II in both the rat and dog studies. Collectively, these observations in dogs and rats suggest that des-Asp-1-angiotensin II may mediate the response to the renin-angiotensin system at both adrenal and renal receptors.

Lanthanum: inhibition of ACTH-stimulated cyclic AMP and corticosterone synthesis in isolated rat adrenocortical cells.

Abstract: Lanthanum (La+++) is a well-known Ca++ antagonist in a number of biological systems. It was used in the present study to examine the role of Ca++ in the regulation of adenyl cyclase of the adrenal cortex by ACTH. In micromolar concentrations, .La+++ inhibited both cyclic AMP and corticosterone response of isolated adrenal cortex cells to ACTH. However, a number of intracellular processes were not affected by La+++. These include the stimulation of steroidogenesis by dibutyryl cyclic AMP, conversion of several steroid precursors into corticosterone, and stimulation of the latter by glucose. Thus, inhibition of steroidogenesis by La+++ appears to be solely due to an inhibition of ACTH-stimulated cyclic AMP formation. Electron microscope examination showed that La+++ was localized on plasma membrane of the cells and did not appear to penetrate beyond this region. Since La+++ is believed to replace Ca++ at superficial binding sites on the cell membrane, it is proposed that Ca++ at these sites plays an important role in the regulation of adenyl cyclase by ACTH. Similarities in the role of Ca++ in "excitation-contraction" coupling and in the ACTH-adenyl cyclase system raise the possibility that a contractile protein may be involved in the regulation of adenyl cyclase by those hormones which are known to require Ca++ in the process.

Receptor binding of angiotensin II and antagonists. Correlation with aldosterone production by isolated canine adrenal glomerulosa cells.

Abstract: The binding properties of the angiotensin II receptors of the adrenal cortex have been studied in isolated cells prepared by collagenase dispersion of the zona glomerulosa of the canine adrenal gland. Such cell preparations are responsive to physiological concentrations of angiotensin II, and permit correlation of binding of angiotensin II and its analogues with aldosterone production in vitro. Uptake of 125I-angiotensin II (5 X 10(-11) M) by glomerulosa cells at 37 degrees C reached a steady state at 45 minutes, with a subsequent plateau for at least 60 minutes. Angiotensin II binding was also dependent upon the hormone and cell concentrations employed during uptake studies. Bound angiotensin II was rapidly dissociated from canine adrenal cells after addition of the unlabeled octapeptide. High affinity sites with equilibrium association constant (Ka) of 3.3 X 10(9) M-1 comprised 25-33% of the receptor population and the remainder of the sites were of lower affinity, 2.5 X 10(8)M-1. Binding of angiotensin II analogues and antagonists was found to be consistent with their biological activities. The analogue most extensively evaluated was [Sar-1]angiotensin II, which exhibited enhanced binding activity when compared to angiotensin II, and had a higher equilibrium association constant by kinetic analysis and direct binding studies. Direct binding of labeled angiotensin II to the adrenal glomerulosa receptor has been correlated with a progressive response in aldosterone production. The steroidogenic response to angiotensin II was maximal when 25% of the receptor population was occupied; this fraction corresponds to the proportion of high affinity receptor sites measured by binding analysis. In addition, inhibition of angiotensin II binding to receptor sites by the competitive antagonist [Sar-1, Ala-8]angiotensin II has been correlated with inhibition of aldosterone production. These findings serve to demonstrate the biological significance of the angiotensin II binding sites of the adrenal cortex, and confirm their role as receptors which mediate the steroidogenic responses to angiotensin II.

Changes in cardiovascular and adrenal cortical responses to angiotensin III induced by sodium deprivation in the rat.

Abstract: The restriction of dietary sodium intake is known to depress the cardiovascular responses to angiotensin II and increase the sensitivity of the adrenal zona glomerulosa to this steroidogenic octapeptide. In sodium-repleted animals, angiotensin III is a weak pressor substance and a potent stimulant of aldosterone biosynthesis. The effect of a low sodium diet on vascular and steroidogenic responses to angiotensin II and angiotensin III was investigated. In nephrectomized rats, angiotensin III had one-third of the pressor activity relative to angiotensin II when either normal or sodium-deprived animals were compared. When administered subcutaneously (sc) to rats, angiotensin II and III induced comparable steroidogenic responses, whereas only angiotensin II significantly elevated blood pressure. The comparison of cell suspensions from control adrenals with suspensions of adrenals from sodium-deprived animals showed that the zona glomerulosa from rats on low sodium diets had increased wet weight (20%), cell protein (25%), and basal steroidogenic rats (45%). Adrenocorticotropic hormone (ACTH)-induced responses in adrenal cells from low sodium animals were about twice the responses of cells from normal adrenals. Angiotensin II and III stimulated the cortex at a threshold concentration of 5 X 10(-10) M and induced a maximum response at about 5 X 10(-8) M in cells prepared from normal rat adrenals. In cells dispersed from adrenal capsules of sodium-deprived rats, the maximal steroidogenic response to angiotensin II occurred at 3 X 10(-8) M, whereas angiotensin III was maximal at 1 X 10(-9) M. Aldosterone synthesis induced by both peptides was increased approximately 45% in adrenal cells from low salt rats. At 0.9 mumol/kg, sc, Sar-1, Ile-8-angiotensin II antagonized cardiovascular responses to angiotensin II and did not alter aldosterone in the sodium-deprived rat. In contrast, treatment with Ile-7-angiotensin III blocked the adrenal cortex but not the vascular actions of angiotensin II. These data are consistent with a role for angiotensin III in the renin-angiotensin-aldosterone response to sodium deprivation.

Organ specificity of angiotensin II and Des-aspartyl angiotensin II in the conscious rat.

Abstract: Des-Asp angiotensin II (des-Asp AII) is a naturally occurring heptapeptide metabolite of angiotensin II (AII) which is formed by the enzymatic action of aminopeptidase A. Angiotensin II and des-Asp AII were infused into unanesthetized rats while direct mean arterial pressure, serum aldosterone and serum corticosterone were measured. Both AII and des-Asp AII caused a dose-related increase in serum aldosterone with a significant increase occurring with a dose as low as 1 ng/min. This effect was blocked by pretreatment with 1-Sar-8-Ala-angiotensin II, a competitive inhibitor of AII; however, the inhibitor was more effective in blocking the effects of AII (101%) than of des-Asp AII (82%). Both angiotensins induced a dose-related increase in serum corticosterone and mean arterial pressure. Des-Asp AII was however only 1/10 as potent as AII in elevating mean arterial pressure. 1-Sar-8-Ala-AII was also effective in inhibiting the pressor effects of AII and des-Asp AII. These data illustrate a high degree of organ specificity or selectivity for des-Asp AII and a low specificity for AII. Aminopeptidase A and leucine aminopeptidase were identified in the adrenal cortex and medulla in large amounts. Des-Asp AII may thus be formed from AII locally in the adrenal gland prior to exerting its action at that site.

Actions of angiotensin II antagonists upon aldosterone production by isolated adrenal glomerulosa cells.

Abstract: The biological activities of angiotensin II antagonists upon basal and angiotensin II-stimulated aldosterone production were evaluated in an isolated canine glomerulosa cell preparation. The most potent competitive antagonist of angiotensin II-stimulated aldosterone production was the [Sar1, Ile8]derivative of angiotensin II. However, this peptide was also a partial agonist at concentrations required to inhibit the steroidogenic effect of angiotensin II on dog adrenal cells, and never reduced aldosterone production to basal levels. On a molar basis, the [Sar1, Ala8] and [Sar1, Gly8]derivatives of angiotensin II were relatively less potent as competitive inhibitors of angiotensin II-stimulated aldosterone production. However, the [Ala8] and [Gly8]- analogues did not exhibit significant agonist activity and were therefore more effective antagonists of angiotensin II-stimulated aldosterone production. These results suggest that increased length of the aliphatic side chain at the C-terminus of angiotensin II ...

Adrenocortical response to marathon running.

Abstract: Plasma cortisol and plasma aldosterone levels were measured before and immediately upon completion of a marathon run in 7 highly conditioned male subjects in order to evaluate the response of the adrenal cortex to physical exertion. Both cortisol and aldosterone values rose significantly in response to the stress of the muscular exertion of the 26 mile, 385 yard run.

Angiotensin antagonists and the adrenal cortex and medulla.

Abstract: Several analogs of angiotensin in which the phenylalanine in position 8 of the peptide chain was replaced by an aliphatic amino acid residue are specific antagonists of angiotensin in aorta, the adrenal medulla, and adrenal zona glomerulosa. In the adrenal cortex and medulla, all actapeptide analogs have more agonist activity than in aortic strips. In studies with N-terminally substituted analogs, it appears that adrenal degradation of the angiotensin molecule by aminopeptidase(s) does not occur or is not retarded by N-terminal mocifications such as sarcosine substitution. The decapeptide analog [Ile8]-angiotensin I and heptapeptide analog [des-Asp1, Ile8]-angiotensin II were excellent antagonists in the adrenal medulla and each peptide was devoid of intrinsic activity. These substituted homologs of angiotensin may offer a novel approach for the development of selective antagonists of angiotensin receptors. In the adrenal cotex, [des-Asp1, Ile8]-heptapeptide possessed greater receptor affinity than any of the angiotensin octapeptides studied. This C-terminally substituted heptapeptide does have significant intrinsic activity in the adrenal cortex which would limit the use of this compound as an antagonist of vascular responses to angiotensin II. In studies with [Ile8]-angiotensin II, [Sar1, Ile8]-angiotensin II, and [des-Asp1, Ile8]-angiotensin II, the pA2 values calculated indicate that the N-terminal residue is not important for receptor binding in the adrenal cortex but may be of significance in binding to adrenal medullary and aortic smooth muscle receptors. At the present time it appears unlikely that any single animal model or assay system can reliably predict the agoinst/antagonist activities of angiotensin analogs for all the various end organs which respond to the angiotensins.

Pituitary and adrenal control of pancreatic endocrine function in the duck. II. Plasma free fatty acids, aminoacids, and insulin variations following hypophysectomy and replacement therapy with growth hormone and corticosterone.

Abstract: The levels of plasma free fatty acids, aminoacids and insulin were studied in normal, hypophysectomized and beef growth hormone and/or corticosterone treated hypophysectomized ducks Hypophysectomy decreased plasma free fatty acids, aminoacids and insulin levels; growth hormone and growth hormone + corticosterone treatments in hypophysectomized animals induced opposite changes, while corticosterone alone only increased the concentrations of plasma aminoacids and insulin However, corticosterone enhanced the growth hormone effects on the three parameters It is suggested that four feed-back mechanisms may be involved in the control of glucagon secretion by the anterior pituitary and the adrenal cortex : glucose-glucagon, free fatty acids-glucagon, aminoacids-glucagon and insulin-glucagon In addition, in these experiments, insulin and glucagon always varied in opposite directions

Radiology in primary hyperaldosteronism

Abstract: Autonomous hypersecretion of aldosterone (primary hyperaldosteronism) is caused by either hyperplasia (usually bilateral) or an adenoma (frequently unilateral) of the adrenal cortex. Systemic hypertension due to an aldosteronoma is a potentially curable condition through surgical extirpation of the offending organ. In our experience with 37 patients clinically suspected to have primary hyperaldosteronism, radiological methods contributed significantly in preoperative diagnosis. These included (1) selective bilateral adrenal vein catheterization and blood sample collection, (2) adrenal venography, and (3) radioisotope adrenal scan. Unilateral hyperfunction could be accurately detected by the aldosterone assays from the collected samples. When adrenal venography was technically satisfactory, a nodule or aggregate of nodules measuring at least 7 mm and located on the margin of the gland or 1.5 cm or more in diameter when located in the center of the gland were readily identified. Enlarged adrenal gland on venography, in itself, was not a dependable index of a hyperfunctioning gland. Presence of a higher uptake on one side on the radioisotope adrenal scan did not always indicate the hyperfunctioning gland, but lack of lateralization of adrenal hyperfunction was more accurately predicted on the radioisotope scan than by venography. Four histopathological patterns were recognized in the surgically removed adrenal glands, but no correlation between these patterns and clinical behavior or postoperative course was found.

Effect of variations in pituitary-adrenal activity on dopamine-beta-hydroxylase activity in various regions of rat brain.

Abstract: Since noradrenergic neurons in the brain appear to inhibit ACTH secretion and dopamine-β-hydroxylase (DBH) is found in noradrenergic neurons, the effect of variations in pituitary-adrenal activity on the activity of DBH in the brain stem, hypothalamus and hippocampus was determined. There was no significant circadian fluctuation in hypothalamic or brain stem DBH, as measured by the coupled radioenzymatic method of Molinoff et al. [1971]. Pentobarbital and ether anesthesia, injection stress and surgical stress also had no acute effect. There was a decrease in anterior hypothalamic DBH 30 min after immobilization stress. Two days after adrenalectomy, there was a decrease in DBH in the hypothalamus and brain stem. A large dose of corticosterone (B) caused an increase in hypothalamic DBH. However, a smaller dose of B which increased plasma B to values comparable to those produced by endogenous secretion failed to have this effect. The data demonstrate an effect of the adrenal glands on brain DBH activity, but it is as yet uncertain whether this effect is mediated by glucocorticoids.