Abstract
Summary: Serum from dogs with anemia secondary to infection, malignancy and chronic renal disease was tested for the capacity to inhibit in vitro erythropoiesis. Serum inhibition was found in seven of 10 dogs with infectious diseases, four of 10 dogs with malignant diseases, and two of 10 dogs with chronic renal failure. The results were reproducible with at least three different marrow donor dogs. Serum inhibition did not correlate with decreased packed cell volumes. However, serum inhibition occurred in the two dogs with greatest azotemia suggesting that inhibitors of erythropoiesis are present only in advanced stages of renal failure.