Endothelin influences pHi of human platelets through protein kinase C mediated pathways.
Stimulation of human platelets with endothelin raises cytosolic pH (pHi). In order to determine whether this effect is mediated via protein kinase C and Na(+)-H+ linked pathways, the effects of staurosporine and calphostin C (protein kinase C inhibitors) and 5-(N,N-hexamethylene) amiloride (Na(+)-H+ exchange blocker) on endothelin-induced pHi responses in human platelets were assessed. In addition, platelet endothelin receptor subtypes were determined pharmacologically using the selective ETA receptor antagonist BQ-123 and the ETB receptor agonist sarafotoxin S6c. pHi was measured spectrofluorometrically using the fluorescent probe BCECF-AM in platelets obtained from 15 healthy subjects. Endothelin-1 at a fixed concentration of 10(-9) M significantly increased pHi from 7.11 +/- 0.01 ([H+]i = 77 +/- 0.9 nM) to 7.19 +/- 0.04 ([H+]i = 64 +/- 0.9 nM) (p < 0.01). The pHi-stimulating effect of endothelin-1 was inhibited by 10(-7) M staurosporine, calphostin C and 5-(N,N-hexamethylene) amiloride. BQ-123 (10(-7) M) abolished the pHi responses to endothelin-1, whereas sarafotoxin S6c had no effect on platelet pHi. These data suggest that in vitro effects of endothelin-1 on platelet pHi are receptor-mediated via a pathway involving protein kinase C. Platelet endothelin receptors appear to be of the ETA subtype.
Touyz
R M
RM
Clinical Research Institute of Montreal, University of Montreal, Quebec, Canada.
Larivière
R
R
Schiffrin
E L
EL
D000328:Adult; D001792:Blood Platelets / Q000187:drug effects*; D003600:Cytosol / Q000378:metabolism; D016232:Endothelins / Q000494:pharmacology*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008297:Male; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism
D016232:Endothelins; D017923:Sodium-Hydrogen Exchangers; D011493:Protein Kinase C