ERYTHROPOIETIN PRODUCTION IN THE RAT ADDITIVE ROLE OF KIDNEY AND LIVER

Erythropoietin (Ep) levels were evaluated in serum of neonate, weanling or adult rats subjected to sham operation, nephrectomy and/or subtotal hepatectomy and a standard bout of hypoxia (0.45 atm air/6 h, starting 1 h after the operation). Ep activity was quantitated by strictly controlled assays in exhypoxic polycythemic mice. The sum of Ep titers in the serum of nephrectomized or hepatectomized rats was compared to Ep levels in sham-operated animals of corresponding age levels, with the exception of 1 wk old rats; no significant difference was apparent between these Ep production curves. Evidence indicated for the 1st time that Ep derives from 2 functionally distinct and additive sources, i.e., the kidney and the liver. Liver Ep, although prevalent in neonatal animals, is obscured in the weanling adult rat by both gradual initiation of massive renal Ep production and progressive decrease of hepatic Ep activity.