Effect of protein kinase-C depletion on inositol trisphosphate-mediated and cyclic adenosine 3',5'-monophosphate-dependent protein kinase-mediated adrenocorticotropin secretion.
We studied the effect of Ca2+/phospholipid-dependent protein kinase-C (protein kinase-C) down-regulation by chronic exposure to phorbol 12-myristate 13-acetate (PMA) on ACTH secretion by dispersed male rat anterior pituitary cells in a microperifusion system. Preincubation for 24 h and preperifusion for 3 h with 0.1 and 1 microM PMA significantly inhibited (by 85% and 91%, respectively) the specific cell binding of [3H]phorbol 12,13-dibutyrate, an index of protein kinase-C concentration, and significantly reduced (by 101% and 20%, respectively) the sustained plateau (final 15-min) phase of the ACTH response to arginine vasopressin (AVP) and (by 56% and 54%, respectively) the sustained (full 20-min) response to dioctanoylglycerol (DOG), both of which are mediated by protein kinase-C activation. In contrast, the spike (initial 5-min) phase of the response to AVP, which is mediated by intracellular Ca2+ release from inositol 1,4,5-trisphosphate (InsP3)-sensitive stores, was significantly increased (by 112% and 99%, respectively), but the spike-type response to ionomycin, which releases intracellular Ca2+ by an InsP3-independent mechanism, was unaffected. AVP significantly stimulated inositol bisphosphate and InsP3, but not inositol monophosphate, accumulation, and PMA pretreatment significantly enhanced their AVP-stimulated accumulation (by 86%, 34%, and 78%, respectively), an effect that was abolished by simultaneous preperifusion with PMA and cycloheximide to inhibit new protein synthesis. Enhancement of the spike phase response to AVP and AVP-stimulated InsP3 accumulation were lost within 1 h of PMA removal, but [3H]phorbol 12,13-dibutyrate binding and the sustained responses to AVP and DOG remained suppressed after 3 h. Pretreatment with 0.1 and 1 microM PMA slightly reduced the sustained responses to CRF (by 29% and 16%, respectively) and 8-bromo-cAMP (by 8% and 12%, respectively), which are mediated by protein kinase-A activation and extracellular Ca2+ influx via L-type voltage-sensitive Ca2+ channels, but not the response to KCl, which is mediated by extracellular Ca2+ influx via all types of voltage-sensitive Ca2+ channels. The sustained response to CRF was still suppressed 1 h after PMA removal, but returned to the control level by 3 h. When new protein synthesis was inhibited by preperifusion with cycloheximide alone for 3 h after 24-h PMA pretreatment, recovery from the effects of PMA was abolished. Three-hour exposure to cycloheximide without PMA pretreatment inhibited the sustained responses to CRF, AVP, and DOG, but not the spite response to AVP.(ABSTRACT TRUNCATED AT 400 WORDS)
Won
J G
JG
Department of Medicine, Veterans General Hospital-Taipei, Taiwan, Republic of China.
Nicholson
W E
WE
Ching
K N
KN
Orth
D N
DN
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D003513:Cycloheximide / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D015759:Ionomycin / Q000494:pharmacology; D008297:Male; D010477:Perfusion; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D004075:Diglycerides; C044295:1,2-dioctanoylglycerol; D001127:Arginine Vasopressin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D015240:Phorbol 12,13-Dibutyrate; D015759:Ionomycin; D011189:Potassium Chloride; D015544:Inositol 1,4,5-Trisphosphate; D000324:Adrenocorticotropic Hormone; D003513:Cycloheximide; D000242:Cyclic AMP; D011494:Protein Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate