INFLUENCE OF DISAPPEARANCE RATE AND DISTRIBUTION SPACE ON PLASMA CONCENTRATION OF ERYTHROPOIETIN IN NORMAL RATS.

Abstract Endogenous and exogenous erythropoietin disappears from the plasma of normal rats in an exponential fashion and with a velocity constant k of 0.32. The distribution space v of erythropoietin equaled twice the plasma volume and was found to be independent of plasma concentration c or rate of formation p. The kinetics of the hormone can therefore be described by the equation c=p (1− e −kt )/kv. The numerical value of k implies that 99 per cent of the final plasma concentration is reached in the normal rat within 16 hours at any given rate of formation. In steady states, therefore, the erythropoietin present in 1 ml. of plasma equals one hundredth of the total erythropoietin formed in the rat during 24 hours.