The alpha-adrenergic stimulation of atrial natriuretic factor expression in cardiac myocytes requires calcium influx, protein kinase C, and calmodulin-regulated pathways.
It has been shown recently that alpha-adrenergic agonists can stimulate atrial natriuretic factor (ANF) expression in ventricular cardiac myocytes; however, little is known about the intracellular signals mediating this activation. The present study focused on the potential roles of calcium-regulated kinases and calcium influx in the alpha-adrenergic stimulation of ANF gene expression in ventricular myocardial cell cultures. Myocardial cells maintained for 48 h in serum-free medium supplemented with phenylephrine (PE) possessed up to 15-fold higher levels of ANF peptide and ANF mRNA than control cells. The removal of PE, or the addition of nifedipine, resulted in a rapid decline in ANF expression, suggesting that the sustained elevation of some intracellular messenger (e.g. calcium and/or phospholipid hydrolysis products) was required for the adrenergic response. The calcium channel agonist BAY K 8644 was capable of increasing ANF expression in a nifedipine-sensitive manner; however, unlike PE, it did not stimulate phosphoinositide hydrolysis. The protein kinase C inhibitor, H7, caused an approximate 75% reduction in PE-stimulated ANF expression, but had no effect on BAY K-stimulated expression. W7, a calcium/calmodulin inhibitor, completely blocked the effects of both PE and BAY K 8644. The addition of either H7 or W7 24 h after the PE addition resulted in a decline of ANF expression. These results indicate that alpha-adrenergic agonists augment ANF gene expression through at least two pathways, one that is H7-sensitive, perhaps involving the sustained activation of protein kinase C, and the other that is W7-sensitive, perhaps involving the sustained activation of calmodulin-regulated kinases. Further, it appears that BAY K 8644-mediated increases in ANF expression are independent of protein kinase C activation and dependent on calmodulin-regulated events.
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Department of Biology, San Diego State University, California 92182.
Irons
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Sprenkle
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McDonough
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Brown
J H
JH
Glembotski
C C
CC
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000235:genetics*; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002478:Cells, Cultured; D015870:Gene Expression; D006321:Heart / Q000187:drug effects; D006868:Hydrolysis; D007546:Isoquinolines / Q000494:pharmacology; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D013449:Sulfonamides / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D002147:Calmodulin; D007546:Isoquinolines; D010716:Phosphatidylinositols; D010879:Piperazines; D013449:Sulfonamides; D010656:Phenylephrine; C017967:W 7; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D009320:Atrial Natriuretic Factor; C043204:N-(2-guanidinoethyl)-5-isoquinolinesulfonamide; D011493:Protein Kinase C; D009543:Nifedipine; D002118:Calcium