SOME BIOCHEMICAL EFFECTS OF THE GROWTH HORMONE ANALOGUE PRODUCED BY PLEROCERCOIDS OF THE TAPEWORM SPIROMETRA MANSONOIDES ON CARBOHYDRATE METABOLISM OF ADIPOSE TISSUE FROM NORMAL, DIABETIC, AND HYPOPHYSECTOMIZED RATS

Plerocercoids of Spirometra mansonoides produce a functional analogue of mammalian growth hormone (GH). Plerocercoid growth factor (PGF) mimics the growth-promoting actions of GH, but has not been shown to duplicate all of the actions reported for GH. The purpose of this study was to determine the effects of plerocercoid infection (chronic PGF treatment) on glucose metabolism of adipose tissue and to compare the effects to those elicited by insulin and GH in intact, diabetic, and hypophysectomized male rats. Groups of rats were constantly exposed to PGF (via plerocercoid infection) or injected twice daily with bovine GH, insulin, or saline for 10 days. Basal oxidation rates of (U-'14C)glucose to '4CO2 in adipose tissue segments were measured in vitro immediately after tissue removal. Other aliquots of adipose tissue were preincubated in hormone-free medium for 3 hr prior to testing the ability of the tissue to respond to insulin or human GH (hGH) added in vitro. Adipose tissue from PGF-treated intact and hypophysectomized rats had significantly elevated basal glucose oxidation rates, and the tissue was sensitive to further stimulation by insulin or hGH. The results obtained with intact and hypophysectomized rats were essentially the same, indicating that the effects of PGF were not due to suppression of endogenous GH. The basal glucose oxidation rate in adipose tissue from diabetic rats was stimulated (P < 0.01) by PGF, but the tissue was not sensitive to insulin added in vitro. Furthermore, PGF had no effect on body growth or blood glucose concentrations of diabetic rats. Therefore, as is true for mammalian GH, the ability of tissues to respond to PGF was dependent on ambient insulin. The results suggest that plerocercoids produce a somatogenic factor which has a direct and persistent insulin-like effect in adipose tissue.