Biochemical changes in progressive muscular dystrophy: V. Incorporation of leucine-C 14 into protein of various tissues of normal and dystrophic mice

Abstract

Normal and dystrophic mice were injected intravenously with leucine-C 14 at various stages of the disease. Except in the case of the dystrophic muscle where the incorporation increased considerably, all other tissues from dystrophic mice (liver, brain, kidney, spleen, and pancreas) showed a decrease as compared to the normal values of all stages investigated. Maximum increase (dystrophic muscle) or decrease (dystrophic liver, brain, etc.) occurred at 90 days of the disease. Similar results were also observed on the in vitro incorporation of leucine-C 14 catalyzed by cell free preparation of the dystrophic mice muscle. In the case of dystrophic muscle, the increase noted at 90 days was followed by a slight decline in the incorporation. The decrease in the incorporation of leucine-C 14 in the absence of either Mg ++, GTP, ATP, and creatine phosphate was more pronounced in dystrophic muscle than in normal muscle. When ATP and CrP were omitted from the system, a decrease of 81% in the incorporation was observed in the dystrophic muscle, as compared to 48% in the control. Replacement of Mg ++ by CO ++ gave a 48% increase in the incorporation in the normal muscle, but has no effect in the case of the dystrophic muscle. It is suggested that the decrease in the incorporation of leucine-C 14 into dystrophic liver, brain and kidney with a concomitant increase in the dystrophic muscle might be an indication that different mechanism of controls regulate the protein biosynthesis in these organs. Furthermore it is observed that the decrease in protein content of the dystrophic muscle is not due to a decrease in the protein synthesis, since dystrophic muscle incorporates leucine-C 14 at an increased rate as compared to normal.