Endothelin does not affect intracellular calcium ion concentration in the platelets of rats

We recently demonstrated that porcine endothelin increases intracellular calcium ion concentration ([Ca2+]i) in monolayers of cultured vascular smooth muscle cells isolated from rat renal arteries. The present study was designed to examine the effect of porcine endothelin on [Ca2+]i in the platelets of rats. [Ca2+]i was serially measured with the fluorescent dye, fura 2, and the photoprotein, aequorin. Endothelin (10(-9) mol/L, 10(-8) mol/L, and 10(-7) mol/L) did not induce any change in [Ca2+]i in the platelets of rats while thrombin (2 U/mL) dramatically increased [Ca2+]i as measured by these methods. Our results indicate that [Ca2+]i in rat platelets is not influenced by porcine endothelin.