Release of growth hormone from purified somatotrophs: interrelation between Ca++ and adenosine 3',5'-monophosphate.
cAMP is thought to be an essential intracellular mediator in the release of GH from somatotrophs. Ca++ is required in the incubation medium to elicit GH release in vitro. We have carried out studies using a purified preparation of rat somatotrophs to see whether the Ca++ requirement procedes or follows the accumulation of cAMP induced by prostaglandin E2 (which increases adenylate cyclase activity) and 3-isobutyl-1-methylxanthine (a phosphodiesterase inhibitor). Incubation of somatotrophs in low Ca++ medium (less than 85 microM) abolished the release of GH induced by the two secretagogues, while the increase in intracellular cAMP was actually augmented. Thus, Ca++ is required in the incubation medium to express the action of intracellular cAMP.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism*; D013006:Growth Hormone / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D011458:Prostaglandins E / Q000494:pharmacology; D051381:Rats
D011458:Prostaglandins E; D013006:Growth Hormone; D000242:Cyclic AMP; D002118:Calcium