Involvement of protein kinase A in the regulation of intracellular free calcium and phosphoinositide turnover in rat myometrium.
Preincubation of Fura 2-loaded rat myometrial cells with H-8, an inhibitor of protein kinase A, for 1 h reversed the inhibitory effects of 8-(4-chlorophenylthio)-cAMP (CPTcAMP) on the oxytocin-stimulated increase in (Ca2+)i (intracellular free calcium), with an EC50 of 47 microM. H-8 also prevented the inhibition by relaxin and isoproterenol of the oxytocin-induced increase in (Ca2+)i. The EC50 of H-8 in reversing the relaxin effect was 42 microM. H-8 reversal of the effect of relaxin on (Ca2+)i was evident both in the absence of extracellular calcium and in cells pretreated with pertussis toxin. H-8 also reversed the inhibitory effects of relaxin and CPTcAMP on the oxytocin-induced increase in [3H]inositol phosphate formation and [3H]phosphoinositide hydrolysis. Preincubation of myometrial cells for 1 h with H-7, another protein kinase inhibitor, only partially attenuated the inhibition by relaxin and CPTcAMP of the oxytocin-induced increase in (Ca2+)i and [3H]inositol phosphate formation at concentrations 4-5 times greater than those of H-8. Acute (15-min) exposure to phorbol myristate acetate (1.0 microM) did not affect basal (Ca2+)i or the oxytocin-stimulated increases in (Ca2+)i or inositol phosphate formation. These results imply a regulatory role for protein kinase A in the inhibition of the oxytocin-induced increase in (Ca2+)i and inositol phosphate formation by relaxants.
Anwer
K
K
Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston 77030.
Hovington
J A
JA
Sanborn
B M
BM
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D007295:Inositol Phosphates / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D009215:Myometrium / Q000187:drug effects / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012065:Relaxin / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology
D007295:Inositol Phosphates; D007546:Isoquinolines; D010716:Phosphatidylinositols; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D013873:Thionucleotides; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; C053177:N-(2-(methylamino)ethyl)-5-isoquinolinesulfonamide; D012065:Relaxin; D000242:Cyclic AMP; D011494:Protein Kinases; D011493:Protein Kinase C; D007545:Isoproterenol; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium