The relationship between cytosolic Ca2+, sn-1,2-diacylglycerol and inositol 1,4,5-trisphosphate elevation in platelet-activating-factor-stimulated rabbit platelets. Influence of protein kinase C on production of signal molecules.
The temporal and dose-response relationships of platelet-activating-factor (PAF)-induced changes in the concentrations of cytosolic Ca2+ ([Ca2+]i), Ins(1,4,5)P3 and 1,2-diacylglycerol (DAG) were examined. In addition, phosphorylation of protein kinase C (PKC) substrate (40-47 kDa protein) was determined. In high-dose PAF-activated platelets, all three signal molecules increased rapidly and transiently, with the peak Ins(1,4,5)P3 concentration preceding maximal elevation of [Ca2+]i by 5 s. In low-dose PAF-activated platelets there were large increases in [Ca2+]i and dense-granule release, without any increase in Ins(1,4,5)P3 and DAG or 40-47 kDa protein phosphorylation. Staurosporine, a non-specific PKC inhibitor, produced enhanced elevations in the concentrations of Ins(1,4,5)P3, DAG and thromboxane B2, and the duration of the Ca2+ signal in platelets stimulated with a high dose, but not a low dose, of PAF. These results suggest there are both phospholipase C-dependent and -independent changes in Ca2+ homoeostasis. Endogenously activated PKC regulates the formation of signal molecules.
Murphy
C T
CT
School of Pharmacy and Pharmacology, University of Bath, U.K.
Elmore
M
M
Kellie
S
S
Westwick
J
J
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D004075:Diglycerides / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D006706:Homeostasis; D015544:Inositol 1,4,5-Trisphosphate / Q000097:blood*; D007700:Kinetics; D010766:Phosphorylation; D010972:Platelet Activating Factor / Q000008:administration & dosage / Q000494:pharmacology*; D015539:Platelet Activation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011817:Rabbits; D019311:Staurosporine; D013929:Thromboxane B2 / Q000097:blood
C011439:1,2-diacylglycerol; D000470:Alkaloids; D004075:Diglycerides; D010972:Platelet Activating Factor; D013929:Thromboxane B2; D015544:Inositol 1,4,5-Trisphosphate; D011493:Protein Kinase C; D019311:Staurosporine; D002118:Calcium