The Effects of Hypophysectomy and Growth Hormone on the Metabolism of Adipose Tissue of Diabetic Rats

Abstract

Incorporation of ¹⁴C from U-¹⁴C-glucose into fatty acids and CO₂ by epididymal fat was studied in vitro. Simultaneous measurements of glycerol and free fatty acid (FFA) production were also made. Induction of diabetes with streptozotocin (50 mg/kg iv.) markedly inhibited fatty acid synthesis and increased glycerol and FFA production. Total adipose tissue mass was grossly reduced. Hypophysectomy of the diabetic animals reversed these changes. Oxidation of glucose to ¹⁴CO₂ was only slightly affected by any of the procedures. Three hrs. after administration, growth hormone (100/µg/rat) inhibited glucose oxidation and fatty acid synthesis in both hypophysectomized and hypophysectomized-diabetic animals. Similarly, when added in vitro to adipose tissue of hypophysectomized-diabetic rats, growth hormone (1 µg/ml) increased the oxidation of glucose and the incorporation of its carbons into fatty acids. These observations are consonant with the suggestion that both the early, insulin-like and the late, anti-insulin-like effects of growth hormone may be independent of endogenous insulin. The data also indicate that in isolated adipose tissue as in whole animals, the metabolic effects of insulin deficiency can be reversed by hypophysectomy.

Key words

Streptozotocin-Diabetes - Hypophysectomy - Growth Hormone - Glucose Oxidation - Lipolysis