Cyclic AMP-dependent protein kinases in the rat myocardial cytosol

The optimal assay conditions for rat myocardial cytosol protein kinases have been determined. The assay medium contained in 0.25 ml: 40 mM Tris/HCl pH 7.4, 5 mM MgCl2, 600 micrograms histone f1, 10--30 micrograms enzyme protein, 32 microM [gamma-32P]-ATP, with or without additions of 1 microM cAMP. The incubation time at 37 degrees C was 5 minutes. The protein kinase activity in the absence of cAMP decreased with development, while the activity in the presence of cAMP remained unchanged. The protein kinase activity of the left ventricle was higher than that in the right ventricle.