In human platelets, adrenaline stimulated, approximately four-fold, as compared with controls, the phosphorylation of primarily two proteins of apparent molecular weights of 20,000 and 40,000, respectively. Maximum phosphorylation occurred after incubation for 1 min and was inhibited by the addition of either yohimbine, prostaglandin E1, or EGTA. Phosphorylation of the two proteins was accompanied by diacylglycerol formation. The (-)-adrenaline-induced phosphorylation of proteins corresponds to the activation of a calcium-dependent protein kinase partially purified by DEAE-cellulose and Sephadex G150 column chromatography. The enzymatic activity was modulated by addition of (-)-adrenaline and CaCl2, by diolein, and in the presence of membranes or phosphatidylinositol but not phosphatidylethanolamine and phosphatidylcholine. A phospholipid-dependent reaction appears to be involved in the molecular mechanism of action of adrenaline.
L H Block, H Jaksche, P Erne, P Bolli, F R Bühler
The Editorial Board will only consider comments that are deemed relevant and of interest to readers. The Journal will not post data that have not been subjected to peer review; or a comment that is essentially a reiteration of another comment.