CHANGES IN ENZYMES (GOT AND GDH) AND METALS (ZN,MN,AND MG) IN LIVER OF RATS DURING ENDOCRINE IMBALANCE AND CALORIC RESTRICTION

Extract Restriction of essential trace metals in the diet interferes with growth. In this study the converse conditions pertained. Livers from calorie-restricted and hypophysectomized rats (with or without hormone treatment) were analyzed for protein, ribonucleic acid (RNA), deoxyribonucleic acid DNA), Mn, Zn, and Mg content and for enzyme activity of glutamic oxalic transaminase (GOT) and glutamic dehydrogenase (GDH). The data are expressed per unit of DNA in liver. Hypophysectomized rats had reduced amounts of metal and enzyme activity in liver and also decreased protein and RNA: DNA ratios. Calorie-restricted rats with adequate protein intake showed opposite findings. GOT activity was not increased. Injection of insulin or bovine growth hormone into hypophysectomized rats increased liver weight and protein and RNA content, but injection of growth hormone only increased DNA content. Injection of insulin increased Zn, Mn, and Mg content and GDH activity per unit of DNA. These results closely resembled the analyses in liver of a previously reported calorie-restricted group. Injection of growth hormone decreased values per unit of DNA, but only significantly so for Zn, RNA, and protein. Conjoint injection of growth hormone and epinephrine inhibited accretion of protein and reduced expected increments in DNA. The RNA: DNA ratio increased, however, and presumably, Mg and Zn were taken up by the liver cell. Sympathetic stimulation inhibited growth. Activity of GDH in liver paralleled the Zn: DNA ratio, and the latter closely followed fluctuations in the RNA: DNA ratio. Activity of GOT, normally directed toward gluconeogenesis, increased in the absence of protein accretion. Speculation Zn and Mn play important intermediate roles in the action of hormones, particularly growth hormone, at the cellular level. Zn is closely retarded to both enzyme activity and RNA activity and to protein synthesis. The Mn: DNA ratio in liver reaches constancy at weaning, and departures from expected values at postweaning may represent changes in mitochondrial mass under abnormal conditions. The similarity in the analyses of liver of hypophysectomized rats treated with insulin and of calorie-restricted rats may indicate that insulin activity is more influential than is growth hormone activity during caloric restriction with adequate protein intake. © International Pediatrics Research Foundation, Inc. 1969. All Rights Reserved.