Abstract
Utilization of dietary protein in vitamin B_<12> (B_<12>)-deficient rats was evaluated by determination of plasma proteins levels, hepatic xanthine oxidase activity, and urinary excretion of nitrogen compounds after the rats had been fed on the B_<12>-deficient soy bean protein diet for 90 days. It was confirmed that the rats was extremely B_<12>-deficient for distinct increase in urinary methylmalonic acid and marked decrease in hepatic B_<12> contents. Growth of the B_<12>-deficient rats was significantly retarded as compared with the ad libitum-feeding control rats and the pair-feeding control rats. Plasma total protein and albumin levels in rats fed on the B_<12>-deficient diet decreased, compared with the pair-feeding control, although the increase in urea-nitrogen was observed. And the decrease of hepatic xanthine oxidase activity was observed in the B_<12>-deficient rats. The excretion of urinary nitrogen compounds, such as urea-nitrogen, allantoin, and creatinine, were all significantly decreased by B_<12>-deficiency compared with the pair-feeding control. The above results suggested that extreme B_<12>-deficiency depressed the utilization of dietary protein in rats. Moreover, adaptation to decrease of dietary protein utilization due to the B_<12>-deficiency was possibly supposed.
