Elevated thrombocyte calcium content in uremia and its correction by 1 alpha(OH) vitamin D treatment.

Intracellular calcium plays an important role in the regulation of platelet function. It has also been demonstrated that platelet functions are impaired in uremia. A rise in intracellular calcium has been shown in several tissues and has been held responsible for the impaired function of several organs seen in uremia. This study was undertaken to evaluate whether the calcium (Ca) content of thrombocytes is elevated in uremia and, if so whether treatment with an active vitamin D metabolite might correct this abnormality. In 10 patients on chronic hemodialysis, platelet Ca content was determined by a technique utilizing consecutive freezing and thawing of platelet-rich plasma. The platelet Ca content of uremic patients was found to be markedly higher (20.86 +/- 0.9 ng/200,00 platelets, p less than 0.01) than that of a group of 20 normals (12.8 +/- 1.2 ng/200,000 platelets). 1 months after treatment with 1 alpha (OH) vitamin D at a dosage of 0.5-2.5 microgram/day, the platelet Ca content of the dialysis patients decreased to 14.99 +/- 2.14 ng/200,000 platelets (p less than 0.05). The data show that in dialysis patients the platelet Ca content is markedly elevated in comparison with that of normals, and the treatment with 1 alpha (OH) vitamin D may significantly reverse this abnormality. It is suggested that elevated Ca content may play a role in the pathogenesis of uremic platelet dysfunction, and that 1 alpha (OH) vitamin D administration may be of benefit in correcting this disorder.