Regulation of the calcium slow channel by cyclic GMP dependent protein kinase in chick heart cells |
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Authors: | George E Haddad Nicholas Sperelakis Ghassan Bkaily |
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Institution: | (1) Department of Physiology and Biophysics, College of Medicine, University of Cincinnati, 45267-0576 Cincinatti, OH, USA;(2) Department of Physiology and Biophysics, Faculty of Medicine, University of Sherbrooke, J1H 5N4 Sherbrooke, Q.C., Canada |
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Abstract: | In order to assess the interaction between the cAMP-dependent and the cGMP-dependent phosphorylation pathways on the slow Ca2+ current (ICa(L)), whole-cell voltage-clamp experiments were conducted on embryonic chick heart cells. Addition of 8Br-cGMP to the bath solution reduced the basal (unstimulated) ICa(L). Intracellular application of the catalytic subunit of PK-A (PK-A(cat); 1.5 M) via the patch pipette rapidly potentiated ICa(L) by 215±16% (n=4); subsequent addition of 1 mM 8Br-cGMP to the bath reduced the amplitude of ICa(L) towards the initial control values (123±29%). Intracellular application of PK-G (25 nM pre-activated by 10–7 M cGMP), rapidly inhibited the basal ICa(L) by 64±6% (n=8). Heat-denatured PK-G was ineffective. Subsequent additions of relatively high concentrations of 8Br-cAMP (1 mM) or isoproterenol (ISO, 1–10 M) did not significantly remove the PK-G blockade of ICa(L). The results of the present study suggest that: (a) 8Br-cGMP can inhibit the basal or stimulated (by PK-A(cat)) ICa(L) in embryonic chick myocardial cells. (b) PK-G applied intracellularly inhibits the basal ICa(L). |
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Keywords: | ICa(L) cyclic nucleotides PK-A PK-G isoproterenol embryo chick heart |
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