[Effect of recombinant human erythropoietin on cytosolic free calcium concentration in platelets]

Intracellular free calcium concentration ([Ca2+]i) was examined in the platelets of 15 control subjects (NT), 6 predialysis patients with chronic renal failure (CRF), 17 patients on hemodialysis (HD), 20 patients on continuous ambulatory peritoneal dialysis (CAPD), 10 normotensive persons with genetic hypertension (GHT) and 8 essential hypertensive patients (EHT). Levels of [Ca2+] i in the platelets were measured by the fluorescent calcium indicator Fura-2. Resting [Ca2+] i in CRF and HD patients was higher than the value in NT and that in CAPD patients was similar to NT. rHuEPO significantly increased the level of [Ca2+] i in CRF and HD patients compared to those in NT. Under resting and EPO-stimulated conditions, the levels of [Ca2+] i in GHT and EHT were higher than those in NT. rHuEPO increased the levels of [Ca2+] i in the absence of extracellular calcium in NT, GHT and EHT. In addition, EPO-stimulated calcium influx in GHT and EHT was greater than that in NT. Thus, it appears that the mechanism of rHuEPO-induced hypertension may be mainly due to elevation of [Ca2+] i. EPO may contribute to the development of genetic hypertension.