Bilateral adrenal enucleation-induced changes in adenohypophyseal pro-opiomelanocortin (POMC)-related peptides synthesis and secretion: a comparative study with adrenalectomized rats.

The aim of the present study was to elucidate the modulatory effect of transient changes in endogenous glucocorticoids, occurring after bilateral adrenal enucleation (ENUC), on anterior pituitary (AP) proopiomelanocortin (POMC)-derived peptides synthesis and output in rats. For this purpose, adult female rats were either bilaterally ENUC, adrenalectomized (ADX), or sham-operated (SHAM) and killed by decapitation 2, 7, 14, and 21 days after surgery. Trunk blood was collected for measurements of ACTH, beta-endorphin (beta-END) and corticosterone (B) concentrations; APs were quickly dissected for the determination of ACTH, beta-endorphin (beta-END)-like (beta-END-LI) and gamma 3-MSH contents and adrenal glands were removed and submitted to histological study.

Evidence for the paracrine action of islet-derived corticotropin-like peptides on the regulation of insulin release.

In view of recent evidence for the endogenous synthesis of proopiomelanocortin (POMC) by pancreatic islets, we have assessed (1) the release of POMC-derived corticotropin (ACTH)-like peptides (ACTH-LP) from isolated perifused rat islets, and (2) the potential paracrine modulatory effect on insulin output of these putative secretagogues. Islets perifused at a glucose concentration of 3.3 mmol/L secreted ACTH-LP at 0.

Modulation of ornithine decarboxylase activity by prolactin in seminal vesicles of the rat.

The stimulatory effect of prolactin on sexual accessory glands is well established, though the mechanism of trophic action remains poorly understood. We have therefore assessed the effect of high levels of prolactin on ornithine decarboxylase activity and polyamine content in seminal vesicles (SV) of adult rats. Hyperprolactinaemia was induced by implantation of tissue fragments of a prolactin-secreting tumour 7315a, and the rats killed at 35 days post-inoculation.

Glucose-induced secretion of ACTH-like products by rat pancreatic islets.

This work was performed to study the release of proopiomelanocortin (POMC)-derived peptides from isolated pancreatic islets and the effect of ACTH--a member of that peptide family--on insulin secretion. Islets were incubated with 3,3 and 16.6 mM glucose and insulin and ACTH-like products (ACTH-LP) were measured by radioimmunoassay.