Effects of melanotropic peptides on fetal adrenal gland.

Abstract

A B S T R A C T Adrenal glands from early, mid, and late fetuses of rabbit, guinea pig, and rat, and from newborn animals of each species, were incubated for 1-4 h with and without 0.1 nM-1 ,uM ACTH, a-or ,B-melanocyte-stimulating hormone (aMSH or ,3MSH).The effects of the peptides were measured on production of glucocorticoids, and on incorporation of labeled thymidine or leucine into DNA or protein, respectively. The findings were similar in all three species. ACTH stimulated synthesis of glucocorticoids throughout fetal life. Potency increased progressively, as reflected by declining minimal effective dose and rising maximal response. In early and mid fetus aMSH and fMSH caused a modest glucocorticoid steroidogenic effect. ACTH and aMSH stimulated DNA and protein synthesis in the early and mid fetal gland. aMSH was more potent than ACTH in these respects, minimal effective dose being generally 10 times less and maximal response 25-200% greater. The effects diminished or disappeared in the late fetal and newborn gland. These data indicate that a-and 8M SH possess steroidogenic or growth-promoting properties, or both, for the fetal adrenal gland.

Changes in Dopaminergic Control of Circulating Melanocyte-Stimulating Hormone-Related Peptides at Puberty

“…A similar trophic effect of a-MSH on adrenal gland was also reported in the fetus (22). Considering the negative correlation existing between DHEA-S and a-MSH response to domperidone, the actual study suggests that a role for a-MSH could possibly be hypothesized also for human adrenarche (22).…”

“…Confirming the in vitro steroidogenic effects of melanotropic hormones, such a treatment was accompanied by an increase in the ACTH 1-13 pituitary content (21). A similar trophic effect of a-MSH on adrenal gland was also reported in the fetus (22). Considering the negative correlation existing between DHEA-S and a-MSH response to domperidone, the actual study suggests that a role for a-MSH could possibly be hypothesized also for human adrenarche (22).…”

Plasma Alpha-Melanocyte-Stimulating Hormone during the Menstrual Cycle in Women

“…In this regard it is noteworthy that recently Coates et al [17] demonstrated that desacetyl-a-MSH is the major form of a-MSH in a-MSH-containing isles located inside human adult anterior hypophysis and, additionally, a-MSH re lease does not seem to need previous acetylation in mammals [18], The functional significance of desacetyla-MSH and of its changes during the menstrual cycle as well, is unknown at present. Like a-MSH, desacetyl-a-MSH might participate in the regulation of the adrenal function [ 19,20] or exert a trophic action on the adrenal tissue [21,22]. Furthermore, a-MSH peptides are con sidered to be endogenous antagonists of opioid peptides [23], Since opioid peptides have profound effects on reproductive functions especially on the ovulatory pro cess [24,25], it is tempting to speculate that the various forms of a-MSH might have the role of counteracting opioid function in this crucial event of the reproductive process.…”

Biosynthesis of Pairs of Peptides Related to Melanotropin, Corticotropin and Endorphin in the Pars Intermedia of the Amphibian Pituitary Gland

“…The tryptic and chymotryptic maps, however, demonstrate that product I is neither a-melanotropin nor des-AcaN-r-melanotropin. It also cannot be the recently described bovine melanotropic peptide [N, O-diacetyl-serine'la-melanotropin [22], as a (c1iymo)tryptic map of this latter peptide would, with the exception of the N-terminal fragment, correspond to that of a-melanotropin. Neither are its mapping characteristics consistent with a /3-melanotropin-like structure.…”