Studies on protein metabolism in rats fed a tropical diet

ABSTRACT

This thesis is an account of investigations in which a special diet was fed to rats and the resulting effects on protein metabolism studied. The special diet closely resembled a type of diet consumed by poorer Jamaicans; similar diets are implicated in the protein malnutrition common in tropical areas. Rats fed this special diet were compared with others consuming adequate amounts of all the known essential nutrients. It was shown that the special diet was deficient in protein of good nutritional quality, and also in certain vitamins and minerals. The protein deficiency was chiefly responsible for the growth failure observed. The diet induced an increased susceptibility to Hypoglycin A, a toxic principle derived from the fruit of Blighia sapida. It appeared likely that this was a result of depressed gluconeogenesis. Liver and kidney, but not heart, were found to be depleted of protein. In liver, protein of varying sulphur content appeared equally affected. Serum albumin and globulin were both reduced, with no change in ratio. Respiration rates of tissue slices remained normal. The protein depletion in liver was accompanied by a parallel decrease in succinic dehydrogenase enzyme. Methionine containing radioactive sulphur was used to observe the rates of protein synthesis in tissue of animals fed the special diet. Experiments "in vitro" with liver slices gave inconclusive results, but experiments "in vivo" showed that synthesis of liver, serum and kidney protein was depressed, while that of heart protein was normal. Radioactive measurements on urine and on the non-protein fraction of serum supported the conclusion that protein synthesis was depressed in rats fed the special diet. It appeared that the major effect of the special diet was to decrease the rate of protein synthesis in the animals, the result being most apparent in tissues normally containing appreciable stores of labile protein (AU)