Erythropoietin increases cytosolic free calcium concentration in vascular smooth muscle cells.

Abstract

The underlying pathophysiological mechanism leading to raised blood pressure after treatment with erythropoietin is a point of much discussion. Direct vasopressor effects of erythropoietin have been shown recently. The aim was to determine whether erythropoietin effects cytosolic free calcium concentration ([Ca2+]i in vascular smooth muscle cells. The effect of erythropoietin on ([Ca2+]i was measured with the fluorescent dye fura2 in cultured vascular smooth muscle cells from Wistar Kyoto rats. Mean resting [Ca2+]i was 90.8(SEM 5.6) nM (n = 32). Addition of erythropoietin at concentrations of 100 U.ml-1 and 250 U.ml-1 increased [Ca2+]i to 112.3(5.0) nM (n = 23, p < 0.05) and 128.4(4.0) nM (n = 10, p < 0.01), respectively. Preincubation with erythropoietin caused a dose dependent increase in angiotensin II induced changes of [Ca2+]i in vascular smooth muscle cells. One mechanism of erythropoietin induced hypertension may be an increase in [Ca2+]i in vascular smooth muscle cells.