[Mechanism of beta-endorphin release regulation--evaluation using dispersed cells of the pituitary intermediate lobe].
The intermediate lobe of the rat pituitary gland is a homogeneous population of cells synthesizing and secreting various peptides related to ACTH and lipotropin derived from a common glycoprotein precursor, pro-opiocortin. The release mechanism of beta-endorphin from the pituitary gland has been reported by a few investigators, but the precise mechanism is still unknown. The receptors for a catecholamine present in the intact intermediate lobe of the rat pituitary gland remain functional on the enzymatically dispersed cells which secrete beta-endorphin-like immunoreactivity (beta-EPLI) and synthesize adenosine-3',5'-monophosphate (cAMP). Stimulation of beta-adrenoceptor with 1-isoproterenol enhances the synthesis of cAMP and accelerates the rate of beta-EPLI release. The ability of beta-adrenergic agonists to enhance the synthesis of cAMP appears to be causally related to the physiological response to beta-adrenergic agonists (i.e. enhanced beta-EPLI release). Phosphodiesterase inhibitors (theophylline, 3-isobutyl-1-methyl xanthine), cAMP analogs (dibutyryl-cAMP, 8-bromo-cAMP) and cholera toxin also increase beta-EPLI release. These findings suggest that cAMP may participate in this beta-EPLI release process. Furthermore, dopamine inhibits basal beta-EPLI release and also diminishes l-isoproterenol stimulated beta-EPLI release.
D000818:Animals; D002772:Cholera Toxin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D004298:Dopamine / Q000494:pharmacology; D004723:Endorphins / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010902:Pituitary Gland / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin
D004723:Endorphins; D010726:Phosphodiesterase Inhibitors; D001615:beta-Endorphin; D002772:Cholera Toxin; D000242:Cyclic AMP; D007545:Isoproterenol; D004298:Dopamine