Behavior of Hepatic Gluconeogenic Enzymes, RNA Metabolism and Amino Acid Level in Rats Carrying Transplantable ACTH-Secreting Pituitary Tumors

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Abstract
The metabolic effects of an ACTH-secreting transplantable mammotropic pituitary tumor, strain MtT.F4, were investigated in the rat. The body weight of the rats was not increased, but the liver weight and liver to body weight ratio were increased more than 2-fold and the adrenal weight was enlarged to 6 times that of normal rats. The activities of the hepatic enzymes involved in gluconeogenesis, glucose 6-phosphatase, fructose 1,6-diphosphatase, lactic dehydrogenase, and those of the malic enzyme and malic dehydrogenase were markedly increased. The liver homogenate and supernatant nitrogen, the free amino acid nitrogen content and the glycogen level increased approximately 2- fold. The amount of RNA was elevated 3- fold, whereas the incorporation of orotate into RNA decreased to one third the activity found in control, normal rats. V\fhen the animals bearing the ACTH-secreting pituitary tumors were adrenalectomized, the inci'eased enzyme activities, nitrogen, glycogen and RNA content decreased markedly. However, some of the parameters did not return completely to normal. The enzymatic and metabolic alterations in the liver of the ACTHproducing tumor-bearing host are attributed to increased adrenocortical hormone secretion. The changes are similar to those found in rats treated with exogenous adrenocortical hormones. (Endocrinology76: 902, 1965)