EPO and hypertensive disorder: Several mechanisms underlie EPO-induced hypertension, including increased blood viscosity, and, potentially, a skewed balance between vasoconstrictor and vasodilator prostaglandins with vascular resistance to the vasodilator effects of NO.183 Indeed, in rats treated with EPO, elevated vascular intracellular calcium concentrations were observed, which associated with vasoconstrictor effects that could not be compensated by cGMP upregulation.184