Effects of protein kinase inhibitor (1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7) on protein kinase C activity and adrenergic stimulation of cAMP and cGMP in rat pinealocytes.
Protein kinase C is thought to be involved in the adrenergic regulation of pineal function. In this tissue, norepinephrine increases cAMP and cGMP accumulation through a synergistic dual receptor mechanism involving alpha 1- and beta-adrenergic receptors; the available evidence indicates that the alpha 1-adrenergic stimulation activates protein kinase C, and that this potentiates beta-adrenergic stimulation of pineal cAMP. The role of protein kinase C in the regulation of cGMP is unclear. In the present report, we determined whether an inhibitor of protein kinase C, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7), inhibits pineal protein kinase C and the adrenergic stimulation of pineal cAMP and cGMP. H7 (10(-4) M) reduced soluble protein kinase C activity by 40%. Treatment of intact pinealocytes with H7 for 0-240 min reduced the effects of subsequent norepinephrine (NE) stimulation of cAMP and cGMP accumulation by at least 25%. H7 also inhibited 25-30% the maximum stimulation of both cAMP and cGMP produced by concurrent treatment with isoproterenol and two agents which elevate intracellular Ca2+, ouabain and A23187. However, H7 did not reduce the effects of selective beta-adrenergic activation, indicating that H7 was probably inhibiting the effects of NE by blocking alpha 1-adrenergic potentiation of beta-adrenergic stimulation, not beta-adrenergically activated mechanisms. H7 also reduced the stimulation of cAMP accumulation produced by the combined treatment of isoproterenol and an activator of protein kinase C, 4-beta-phorbol 12-myristate, 13-acetate, which is consistent with the view that H7 is acting by inhibiting protein kinase C activity. These observations are in agreement with the conclusion that potentiation of beta-adrenergic stimulation of cAMP by alpha 1-adrenergic agonists, protein kinase C activators, or [Ca2+]i elevating agents involves protein kinase C. In addition, these results are of special interest because they point to the possibility that protein kinase C is involved in the regulation of cGMP accumulation.
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Section on Neuroendocrinology, National Institute of Child Health and Human Development, Bethesda, MD 20892.
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Klein
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D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D000242:Cyclic AMP / Q000032:analysis*; D006152:Cyclic GMP / Q000032:analysis*; D005260:Female; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D010870:Pineal Gland / Q000032:analysis* / Q000166:cytology; D010879:Piperazines / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000502:physiology*
D007546:Isoquinolines; D010879:Piperazines; D011941:Receptors, Adrenergic; D000001:Calcimycin; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000242:Cyclic AMP; D011493:Protein Kinase C; D006152:Cyclic GMP; D007545:Isoproterenol; D002118:Calcium; D009638:Norepinephrine