Phosphorylation of phosphatidylinositides during muscarinic acetylcholine receptor regulation of myocardium contraction

While estimating the myocardium sarcolemma phosphatidylinositides phosphorylation the muscarime acetylcholine receptor agonist carbacholine (10(-7) M) was determined as capable to stimulate 32P incorporation into phosphatidylinositol-4-monophosphate (in 2.6 times) and phosphatidylinositol-4,5-bisphosphate (in 2.3 times) indicating to the activation of phosphatidylinosite kinase and phosphatidylinosite 4-kinase respectively. The phosphorylation reactions in general completely depend on the presence in the incubation medium of Mg2+ capable in 10 mkM concentration to increase 32P influx into phosphatidylinositol-4-monophosphate 8 times, and into phosphatidylinositol-4,5-bisphosphate 4 times. Carbacholine (10(-7) M) also activates phospholipase C which hydrolyses phosphatidylinositol-4,5-bisphosphate. The latter is substantiated by the increase (2.6 times) of the secondary messenger--inositol-1,4,5-trisphosphate formation.