Metabolism of collagen and muscle protein of adult rats in protein depletion and repletion.

Abstract

The effect of protein depletion and repletion on the contents of rat body collagen and muscle protein has been investigated. Adult male rats were placed on a protein-free diet for 64 days, and thereafter fed with a 20% casein diet for 83 days. Total nitrogen, hydr oxyproline and Nτ-methylhistidine were determined in several tissues. Skin collagen was fractionated into neutral salt-soluble, acid-soluble and insoluble collagen.In prolonged protein depletion, the total amounts of liver protein, skin collagen and muscle protein were markedly decreased, while carcass collagen (excluding skin) showed little effect. The concentrations of skin and carcass collagen were significantly increased in protein depleted rats. Some differences in metabolism between skin collagen and other carcass collagen were discussed.After 64 days of depletion, refeeding on an adequate protein diet brought about a rapid increase in body weight, liver protein and muscle protein. Skin collagen did not increase in the early period of refe...