Hepatic gluconeogenic enzymes, RNA metabolism and amino acid levels in rats carrying transplantable growth hormone-secreting pituitary tumors.

Abstract

The metabolic effects of a growth hormone-secreting transplantable pituitary tumor, strain MtT.W5, were investigated in the rat. Body weight, liver weight and liver/body weight ratio were markedly elevated. However, the rise in adrenal weight was only proportional to the increment in body weight. The following metabolic alterations were observed in the liver as expressed on a per cell basis. The hepatic enzymes examined were markedly increased: glucose 6-phosphatase, 202%; fructose 1,6-diphosphatase, 301%; malic dehydrogenase, 182%; and malic enzyme, 766%. Liver homogenate and supernatant nitrogen and free amino acid nitrogen were elevated to about 200 %. The hepatic glycogen level was increased 3-fold but blood sugar concentrations were in normal range. The liver RNA level was raised to 238 % and the incorporation of labeled orotate into total hepatic RNA was 180 % of the control values. Adrenalectomy did not reverse or affect these hepatic biochemical alterations. Thus, the metabolic effects observed were not due to a hormone action mediated through the adrenal gland. (Endocrinology79: 865, 1966)