Erythropoietin kinetics in normal and uremic sheep

Homologous erythropoietin (Ep)-rich plasma was infused into sheep to determine the kinetics of this hormone in a large animal model. Ep levels after infusion were measured by radioimmunoassay using a sheep standard. Twenty-seven infusions into normal (14), subtotally nephrectomized (11), and anephric (two) animals were analyzed according to a single-compartment model. The volume of distribution was also calculated, and compared with values obtained indirectly from measurement of chromium 51-labeled red blood cells. The data showed that the t 1/2 of the infused hormone was ~9 hours and was independent of renal function. After multiple infusions, the t 1/2 appeared to shorten. The volume of distribution for this hormone corresponded to the plasma volume of the animals. These studies suggest that Ep, if administered to patients with chronic renal failure, could be given infrequently with little dependence on renal function.