Changes in Enzymes (GOT and GDH) and Metals (Zn, Mn, and Mg) in Liver of Rats During Endocrine Imbalance and Caloric Restriction

Abstract

ExtractRestriction of essential trace metals in the diet interferes with growth. I n 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. SpeculationZn 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 mitochondria1 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. 434 CHEEK, GRAYSTONE Changes in enzymes ( G O T a n d GDH) a n d metals (Zn, Mn, and Mg)

An investigation of sites that bind human somatotropin (growth hormone) in the liver of the pregnant rabbit

“…The highest specific (displaceable by excess unlabelled hormone) binding of 1251I-labelled human somatotropin was found in the liver of the late-pregnant rabbit (Tsushima & Friesen, 1973). This is consistent with several of the known actions of somatotropin, such as the stimulation of somatomedin production (McConaghey & Sledge, 1970) and protein synthesis (Korner, 1959) in the liver, and effects on the activities of certain enzymes in the liver, such as glutamate dehydrogenase (Cheek & Graystone, 1969), ornithine decarboxylase and RNA polymerase (Janne & Raina, 1969).…”

Comparisons Between Nucleic Acids, Protein, Zinc, and Manganese in Rat Liver: A Relation Between Zinc and Ribonucleic Acid

“…While Zn deficiency may exist in mammals as a definite entity, the hypothesis can be made that in protein deficiency, as with other situations, RNA content of the cell will fluctuate with the Zn content [3].…”

“…These interrelations are considered for control rats, In an earlier paper [3] it was reported that during a rats receiving adequate protein but inadequate calories, variety of circumstances affecting growth of rats and for rats that had been hypophysectomized. (endocrine imbalance, calorie restriction) the ratios Regression equations presented in this communicain liver of both zinc and ribonucleic acid to deoxyribo-tion contain a common factor, liver weight, through nucleic acid appeared to parallel each other closely.…”

Changes of Trace Minerals (Serum Iron, Zinc, Copper and Magnesium) in Thalassemia

“…This element has been observed to be an integral part of several metalloenzymes including carbonic anhydrase, alkaline phos phatase, pancreatic carboxypeptidase and lactic dehydrogenase. It is also required for synthesis of nucleic acids and protein metabolism [13][14][15][16], Zinc deficiency was once thought impossible in man owing to the wide spread presence of the element in food and water. This concept is now changed.…”