Pathophysiological changes in serum erythropoiesis stimulating activity.

The mouse fetal liver cell bioassay has been used to study serum levels of erythropoiesis stimulating activity (ESA) in patients with a variety of haematological disturbances. The results indicate that this assay system provides a quantitative measurement of ESA, the concentration of which varies predictably in a manner which is consistent with it having a function as an in vivo regulator of erythropoiesis. Dose-response curves for serum ESA show highly significant parallelism with those obtained from sheep plasma erythropoietin and the International Reference Preparation of human urinary erythropoietin.