Effect of platelet release products on cytosolic calcium in cardiac myocytes.
The effect of platelet release products on cytosolic calcium [( Ca++]i) was examined by monitoring the fluorescence of chick embryonic heart cells loaded with the fluorescent calcium indicator indo-1 AM. Cell free filtrate of platelet release products was obtained from rabbit platelets activated with thrombin or collagen. This filtrate caused a rapid increase in both systolic and diastolic [Ca++]i in a dose-dependent manner. The effect was not blocked by pretreating the platelets with aspirin or a thromboxane synthetase inhibitor. It was not mimicked by a thromboxane analog, or by several substances known to be released from platelets including ADP, serotonin, or platelet activating factor. Apyrase or ATP-gamma S had no effect on the activity. The responsible product was heat-sensitive, trypsin-sensitive, and partitioned into the aqueous phase of a chloroform suspension. It has a low molecular weight (less than 3kD) and is sensitive to 2-mercaptoethanol. Protease inhibitor appears to prolong the activity. These results suggest that trypsin-sensitive peptide(s) released from activated platelets can increase [Ca++]i in cardiac cells.
Chien
W W
WW
Division of Cardiology, Stanford University School of Medicine, CA 94305.
Mohabir
R
R
Newman
D
D
Leung
L L
LL
Clusin
W T
WT
D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002457:Cell Extracts / Q000032:analysis / Q000494:pharmacology*; D002642:Chick Embryo; D006321:Heart / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D015539:Platelet Activation; D014020:Tissue Extracts / Q000494:pharmacology*
D002457:Cell Extracts; D014020:Tissue Extracts; D002118:Calcium