[The M-receptor stimulation of phosphatidylinositol metabolism in the isolated rabbit heart].

The activating effect of a M-receptor agonist carbachol on phosphatidylinositol metabolism under perfusion of the isolated rabbit heart with 32Pi was shown. An increase of the inclusion of 32P in phosphatidylinositol-4-phosphate and phosphatidylinositol-4-diphosphate was found. Simultaneously there was detected an elevation of the levels of products of hydrolysis of inositol phospholipids--inositol-1,4-diphosphate and inositol-1,4,5-triphosphate.

[Phosphorylation of myocardial sarcolemma proteins during induction of the phosphatidylinositol cycle in isolated perfused rabbit heart].

Phosphorylation of cardiac sarcolemma proteins under stimulation of M-receptors by agonist carbacholine used to stimulate phosphatidylinositide cycle, was investigated in the isolated, rabbit heart perfused with 32Pi. Carbacholine (10(-7) stimulates the polyphosphoinositide metabolism which is expressed in the activated incorporation of 32P from [gamma-32P]ATP in polyphosphoinositide as well as in the increased content of the labelled inositol trisphosphate released through phosphatidylinositol-4,5-bisphosphate break-down by phospholipase C. The diacylglycerol produced simultaneously with inositol triphosphate as a second messenger activates the protein kinase C.

[Ca2+-phospholipid-dependent phosphorylation of vesicular preparations of myocardial sarcolemma].

A Ca2+-phospholipid-dependent protein kinase C was isolated from the soluble fraction of bovine brain, using hydrophobic chromatography on phenyl-Sepharose CL-4B and high performance liquid chromatography on a Mono Q column. The enzyme had a specific activity of 822 nmol 32P/mg protein/min with histone H1 as a substrate. Phosphorylation of pig myocardium sarcolemma protein substrates was stimulated by Ca2+ and phosphatidylserine; the optimal concentrations of these compounds were 10(-4) M and 200 micrograms/ml, respectively.

[ATP-dependent transport of Ca2+ in myocardium sarcolemma vesicles and its activation by phorbol esters].

Highly purified pig myocardium sarcolemma vesicles possess the Ca2+,Mg2+-ATPase activity (4.1 mumol Pi/mg protein/hour) and induce the ATP-dependent accumulation of 45Ca2+ (6.0 nmol/mg protein/min).

[Relation between the passive transport of calcium into vesicles of the myocardial sarcolemma and membrane potential].

The effect of membrane potential on the passive 45Ca2+ uptake by cardial sarcolemmal vesicles was investigated. Membrane potentials were generated by the K+ gradient in the presence of valinomycin and were measured using fluorescent dye diS-C3-(5). It was shown that the 45Ca2+ influx into vesicles increased twice after membrane depolarization.