Vitamin C metabolism in rats fed a low-protein diet and exposed to cold.

Abstract

Male rats of the Wistar strain were fed a low-protein (5% casein) or a control (20% casein) diet at environmental temperatures of 24 and 5 °C. Measurements were made of daily food intake, body weight, and urinary excretion of vitamin C, and of ascorbic acid synthesis and destruction by liver homogenates in vitro. From the results of several experiments it was observed that (a) rats fed the low-protein diet excreted decreased amounts of vitamin C which were increased by exposure to cold; (b) ascorbic acid synthesis was decreased in rats fed the low-protein diet; (c) ascorbic acid synthesis was increased by cold exposure in rats fed the low-protein diet ad libitum but not when pair-fed; (d) destruction of ascorbic acid was not affected markedly by either dietary protein level or by cold exposure; (e) subcutaneous injection of ascorbic acid (5 mg/100 g body weight) significantly increased body weight gain in rats fed the low-protein diet at 24 and 5 °C and in rats fed the control diet at 5 °C. These observations indicate an inadequate synthesis of ascorbic acid in rats fed a low-protein diet.