Regulation of cardiac cyclic GMP-dependent protein kinase.

摘要: Abstract An assay method based on the ability of high concentrations Mg2+ to stimulate phosphorylation histone in presence low ATP was developed for measurement cyclic GMP-dependent protein kinase activity ratios (activity -cyclic GMP/activity + GMP). In tissues which contain only trace amounts kinase, basal were due interference from a nucleotide-independent kinase. order study regulation cardica factors affecting equilibrium between active and inactive forms enzyme determined. Since rate dissociation GMP its binding site(s) relatively slow at 0–4°C pH 7.0, amount time required process tissue samples major limiting factor preserving enzyme. Dilution heart extracts did not significantly alter ratio under conditions or elevated levels. Experiments using charcoal exogenous homogenizing medium demonstrated that release sequestered responsible elevation by agents like acetylcholine. Therefore, reflected part, least, retention kinase-bound extracts. The effects acetylcholine sodium nitroprusside levels, ratios, force contraction studied perfused rat heart. Both produced rapid, dose-dependent increases cardiac GMP. Optimal 2–3-fold increase levels an ratio. No significant effect observed. Associated witth acetylcholine-induced with reduction contraction. contrast, little no despite increasing level 8–10-fold. Nitroprusside also had contractile force. combination, additive but activation similar those seen alone. results suggest is coupled while not.