Coordinated action of calcium ion and adenosine 3',5'-monophosphate upon the release of alpha-melanocyte-stimulating hormone from the intermediate lobe of the rat pituitary gland.
Stimulation of the release of alpha MSH from dispersed rat melanotrophs by L-isoproterenol, 8-bromo-cAMP, or cholera toxin requires calcium ion (Ca++) in the incubation medium; the stimulatory effect of each of these agents is attenuated by D-600, a Ca++ antagonist. In contrast, stimulation of the formation of cAMP by L-isoproterenol, isobutyl methylxanthine, or cholera toxin does not require Ca++ in the incubation medium. Ca++ diminishes the amount of cAMP formed by cholera toxin-treated melanotrophs. Ca++ inhibits adenylate cyclase activity and enhances cyclic nucleotide phosphodiesterase activity in cell-free homogenates of intermediate lobe tissue. A23187, a calcium ionophore, increases the accumulation of 45Ca by melanotrophs and enhances the release of alpha MSH. Furthermore, when tested upon cholera toxin-treated melanotrophs, A23187 potentiates the Ca++-induced inhibition of cAMP formation. The results indicate that Ca++ is essential for the release of alpha MSH, and that cAMP in some way enhances the effects of Ca++ upon the release process.
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent; D002772:Cholera Toxin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D005711:Gallopamil / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D051381:Rats
D002413:Cations, Divalent; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000001:Calcimycin; D005711:Gallopamil; D009074:Melanocyte-Stimulating Hormones; D002772:Cholera Toxin; D000242:Cyclic AMP; D007545:Isoproterenol; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine