Influence of Dietary Protein Concentration and Quality on Response to Erythropoietin in the Polycythaemic Rat

S ummary . The effects were examined of dietary protein concentration and quality on the response of polycythaemic hypertransfused rats to 6 units of human urinary erythropoietin. Rats were either starved or fed one of 14 different diets. Four protein sources were used, having a quality gradient from 100 to about 24. Two proteins—casein and wheat gluten—were used at five different levels of concentration (5–25%) in the diet. The response of rats maintained on the standard diet (Purina rat chow, 23.4% protein/g) was taken as the normal standard. The response to erythropoietin was 25% of normal in starved rats and 35% of normal in rats put on a protein-free diet. When 10% protein in the diet was obtained by using high biological value proteins (egg yolk or casein) the response to erythropoietin was normal. When the same concentration was achieved by using low biological value proteins (wheat gluten or corn protein) the response to erythropoietin was undistinguishable from that of rats put on the protein-free diet. When rats were maintained on diets with different concentrations of casein (5–25%) a normal response was observed when protein concentration was 10% with no further changes at higher concentrations. When rats were fed diets with different wheat gluten concentrations (5–25%) the response to erythropoietin was subnormal. These data suggest that the ability of rats to respond normally to erythropoietin is dependent on a continuous dietary intake of proteins at levels which are dependent on their biological values.