Showing papers by "Elias Castanas published in 1982"

Adrenocorticotropin,β-Endorphin, and Corticosterone Secretion in Brattleboro Rats*

Abstract: Brattleboro rats which lack endogenous vasopressin have been used to study the role of vasopressin as a corticotropin-releasing factor. Plasma ACTH,β-endorphin, and corticosterone were measured by RIA in male and female Long- Evans and Brattleboro rats under the following conditions: unstressed, after ether stress, after nicotine injection, and after adrenalectomy. A significant reduction in the ACTH, β-endorphin, and corticosterone responses to the different experimental procedures was observed in the Brattleboro rats. However, in this strain of rats, a significant increase in the release of all three hormones was obtained, suggesting that vasopressin has only a synergistic role in the regulation of their secretion.

Enkephalins in human pheochromocytoma biosynthesis and secretion

Abstract: Adrenal medulla has recently been shown to contain high concentrations of enkephalin immunoreactive peptides. In the present study, we report the levels of Methionine-Enkephalin (M-ENK) and Leucine-Enkephalin (L-ENK) in extracts from six cases of human pheochromocytoma. The molecular forms of M-ENK have been characterized by gel filtration chromatography. PRO-M-ENK mRNA extracted from one tumour has been estimated to represent 1% of total mRNA after in vitro translation. M-ENK immunoreactive peptides are secreted in the culture medium of dispersed cultured cells of human pheochromocytoma. This secretion is stimulated when nicotine (10−5M) is added to the medium. Nicotinic stimulation is inhibited by fentanyl (10−5M) or clonidine (10−4M). However, the level of plasma M-ENK in pheochromocytoma patients is not significantly different from normal patients. Data from Faden and Holaday(1) have established that naloxone (an opiate antagonist) a beneficial role in shock, but the origin and meaning of plasma M-ENK remain to be established.

[Effects of electric stimulation of the para-ventricular nucleus on corticotropin function in Long-Evans and Brattleboro rats].

Abstract: Two peptides have a strong corticotropin releasing factor (CRF) activity: arginine vasopressine (AVP) and a 41-residue peptide (41-CRF). Both peptides are present in high concentration in the PVN of the Rat, a zone of the hypothalamus at which electrical stimulation elicits ACTH release. Since homozygous Brattleboro Rats (Di/Di) congenitally lack endogenous AVP, it was of interest to compare the ACTH and corticosterone release after electrical stimulation of the PVN in Long-Evans (L.E.) and Di/Di Rats. In both L.E. and Di/Di Rats, there is a significant increase in plasma ACTH and corticosterone after electrical stimulation of the PVN. However, corticosterone levels are significantly lower in Di/Di than in L.E. Rats whether the Rats have been stimulated or not. It is concluded that a physiological CRF activity is present in the PVN of Di/Di Rats independently of the CRF like activity of AVP.

[Opiate peptides of the adrenal medulla (author's transl)].

Abstract: Significant concentrations of enkephalins are present in the adrenal medulla, notably in man, ox and dog. High molecular weight peptides precursors of enkephalin pentapeptide can also be demonstrated in the same tissue. Although the biosynthesis of enkephalins has not yet been completely elucidated, it seems to follow a pathway different from that of beta-endorphin. The secretion of enkephalins is regulated by the same mechanisms as the secretion of catecholamines. Enkephalins act locally by modulating catecholamine release, but since they are released into the systemic circulation, another, still ill-defined hormonal action is possible.