Alpha-melanocyte stimulating hormone increases plasma levels of glucagon and insulin in rabbits.
Intravenous injections of 25 and 2.5 micrograms alpha-melanocyte stimulating hormone (alpha-MSH) increased plasma levels of glucagon, insulin and free fatty acids in fasted and fed rabbits. 45 micrograms beta-melanocyte stimulating hormone (beta-MSH) had similar effects, whereas 22 micrograms gamma-2-melanocyte stimulating hormone (gamma-MSH) was inactive. The alpha-MSH-induced increases in the plasma levels of glucagon, insulin and free fatty acids were not inhibited by alpha- or beta-adrenergic blocking drugs. The alpha-MSH-induced increases in the plasma levels of insulin were, however, augmented by phentolamine (an alpha-adrenergic receptor blocking drug). The plasma levels of glucose were increased by 25 micrograms alpha-MSH in fed rabbits, only, and were decreased by alpha-MSH during alpha-receptor blockade. The acute in vivo effects of alpha-MSH and beta-MSH on the plasma levels of glucagon, insulin and free fatty acids were rather similar to those previously reported for corticotropin (ACTH). It is possible that the 4-10 ACTH sequence, present in alpha-MSH, beta-MSH and ACTH, but not in gamma-MSH, is a message sequence for the observed effects. However, ORG 2766, a 4-9 ACTH analogue, was inactive. The mechanism by which alpha-MSH increased the plasma levels of glucagon and insulin in rabbits remains to be determined. It is possible, that the effects were mediated by both a central nervous action and a direct action on the endocrine pancreas.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005934:Glucagon / Q000097:blood*; D007328:Insulin / Q000097:blood*; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology*; D011817:Rabbits
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D009074:Melanocyte-Stimulating Hormones; D005934:Glucagon