dietary protein and blood urea levels in rat

previous work by other investigators indicates a direct relation between the amount of protein in the diet and the level of urea in the blood . however, the present report shows that the type of protein , apart from its level in the ration , also has an effect on blood urea concentrations. when adult male or female rats of two strains were fed a ration in which the only source of protein was wheat flour , the blood urea level was 20 percent lower than in rats fed an isonitrogenous ration containing casein. this reduction was apparent in the first blood samples taken one week after the start of the wheat ratio . it was most prominen in the blood samples secured 18 hours after removing the feed cups from the cages . the reduction in blood urea was not due to a decreased digestibility of the flour ration nor to a change in the proportion of urinary nitrogen excreted as urea.