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At least 757 records · Page 42Linked to original sources
PubMed1985

Natriuretic peptides derived from pro-opiocortin.

Natriuresis in response to hypertonicity, volume loads, or high sodium diets has been proposed to be mediated by the release of a humoral factor(s), and controlled by the central nervous system. We have determined that the natriuretic activity of ACTH or alpha MSH resides in a common sequence, ACTH(4-10)/alpha MSH(4-10). Steric restriction of this peptide by replacement of an L-Phe residue with a D-Phe produced a superagonist. Gamma-2 MSH is a peptide derived from the 16K N-terminus of pro-opiocortin, which contains an ACTH(4-10)-like sequence. The natriuretic effect of gamma-2 MSH was maximal between 0.64 pmole to 64 pmole. Doses greater than 128 pmole produced no significant effects on renal sodium excretion. The regulated release of gamma MSH peptides may contribute to CNS regulation of renal sodium excretion.

Adrenocorticotropic Hormone↗
PubMed1986

Characterization of pro-ACTH/endorphin-derived peptides in rat hypothalamus.

The proteolytic processing pattern of pro-ACTH/endorphin in rat hypothalamus is similar to the pattern in the pars intermedia; peptides the size of beta-endorphin, gamma-lipotropin (gamma-LPH), corticotropin-like intermediate lobe peptide (CLIP), alpha-melanotropin (gamma-MSH), joining peptide, and glycosylated gamma 3-MSH all represent predominant end products. Equimolar amounts of beta-endorphin-, alpha-MSH-, CLIP-, gamma-LPH-, and joining peptide-related immunoreactivity are found in hypothalamic extracts (approximately 3 pmol per hypothalamus). Although the proteolytic processing pattern in the hypothalamus is similar to that in the pars intermedia, a tissue-specific posttranslational processing pattern was detected. Ion-exchange analysis of beta-endorphin-sized immunoreactive material from hypothalamic extracts resolves three major forms, corresponding to beta-endorphin(1-31), beta-endorphin(1-27), and beta-endorphin(1-26). The alpha-N-acetylated forms of endorphin represent less than 10% of the total beta-endorphin immunoreactivity. Analyses of hypothalamic alpha-MSH-sized molecules with acetyl- and amide-directed alpha-MSH antisera suggest that hypothalamic alpha-MSH is fully amidated, but largely not alpha-N-acetylated. Fractionation by reverse-phase high-performance liquid chromatography (HPLC) confirms that greater than 85% of the alpha-MSH immunoreactivity corresponds to ACTH(1-13)NH2 or its sulfoxide, and less than 10% corresponds to alpha-MSH [alpha-N-acetyl-ACTH(1-13)NH2] or its sulfoxide. Isoelectric focusing demonstrates that 83-93% of hypothalamic CLIP is phosphorylated. Isoelectric focusing suggests that the majority of the hypothalamic gamma-LPH-sized immunoreactive material is indistinguishable from gamma-LPH synthesized by pituitary melanotropes. The minor extent of alpha-N-acetylation of alpha-MSH and beta-endorphin, the limited carboxyl-terminal proteolysis of beta-endorphin, and the extensive phosphorylation of CLIP represent major differences between the posttranslational processing patterns of pro-ACTH/endorphin in the hypothalamus and pars intermedia.

Acetylation↗
PubMed1986

[Neurochemical characteristics of opioid peptides].

Opioid peptides seem to be involved in an increasing number of cerebral functions. It appears from the most recent studies that these peptides are divided into three families: pro-opio-melanocortin, pro-enkephalin and prodynorphin. Unlike conventional neurotransmitters, these substances are fraught with extremely complex problems of specific biosynthesis and degradation. Finally, the multiplicity of opiate receptors and the search for specific endogenous or synthetic ligands raise major fundamental questions concerning the clinical relevance of studies performed on opioid peptides.

Aminopeptidases↗
PubMed1986

Immunocytochemical localization of pro gamma MSH, gamma MSH, ACTH and beta endorphin/beta lipotrophin in the fetal sheep pituitary: an ontogenetic study.

An immunocytochemical staining technique was used to localize four fragments [pro gamma MSH, gamma MSH, ACTH and beta endorphin/beta lipotrophin (beta endorphin/beta LPH)] of the proopiomelanocortin molecule in both the adult and fetal sheep pituitary. In the adult sheep anterior pituitary each fragment was localized in cells that were darkly stained, stellate and widely distributed throughout the gland. The same cells, identified in three serial sections, stained with anti-pro gamma MSH, anti-ACTH and anti-beta endorphin/beta LPH. In the fetal sheep anterior pituitary all the proopiomelanocortin derived fragments were present at 38 days gestation. Between about 90 and 130 days of gestation both adult type proopiomelanocortin cells (small, stellate) and uniquely fetal cells (large, columnar) were present. Both adult-type and fetal proopiomelanocortin cells were identified in serial sections of the fetal anterior pituitary, stained with anti-pro gamma MSH, anti-ACTH and anti-beta endorphin/beta LPH. The adult intermediate lobe was immunoreactive with anti-pro gamma MSH and anti-beta endorphin/beta LPH but not with anti-gamma MSH or anti-ACTH. The fetal intermediate lobe was immunoreactive with all four antisera from 60 days gestation.

Adrenocorticotropic Hormone↗
PubMed1986

Regulation of proopiomelanocortin (POMC) mRNA levels in primary pituitary cultures.

The effect of a variety of neurotransmitters and of corticotropin releasing factor (CRF) upon levels of mRNA coding for proopiomelanocortin (POMC) was studied in primary cultures of rat pituitary. Total nucleic acid was extracted from cells, fixed on nitrocellulose and hybridized to a single-stranded alpha 32P-labeled DNA complementary to 150 bases of mouse POMC mRNA. After two days incubation with CRF (10(-8) M), the levels of POMC mRNA in both the anterior (AL) and the intermediate lobe (IL) cells increased by about 100%. A similar increase in the IL cells was seen after incubation with the beta-adrenergic agonist isoprenalin (10(-6) M). In contrast, dopamine (10(-6) M) and GABA (10(-6) M) decreased POMC mRNA levels in the IL cells to about 50% of control levels without affecting POMC mRNA levels in the AL cells. In both pituitary lobes, POMC mRNA was decreased by the Ca2+-channel blocker D600 (10(-5) M) and increased by forskolin (10(-6) M). This indicates that both cAMP and Ca2+ ions play an important role as intracellular messengers for the control of POMC gene expression in normal melanotrope and corticotrope cells.

Animals↗