EFFECTS OF INSULIN ON THE INTACT LEVATOR ANI MUSCLE OF THE RAT

Abstract

ABSTRACT Effects of insulin in vitro on the rate of intracellular accumulation of α-aminoisobutyric acid (AIB) and D-xylose were studied in the intact levator ani muscle prepared as described by Arvill & Ahrén (1966 a). In some of the experiments the effects of insulin were also studied in the intact diaphragm preparation of Kipnis & Cori (1957). Insulin increased the rate of uptake of AIB and D-xylose in both preparations. A linear dose-response relationship was found within certain dose levels of insulin for the AIB transport in the levator ani preparation. The sensitivity to insulin of the AIB transport was found to be greater in summer than in winter. Addition of glucose to the incubation medium decreased the rate of penetration of D-xylose into the levator ani muscle but it did not influence the rate of AIB uptake or the effect of insulin on the AIB transport. A rapid reduction of the insulin activity in the incubation medium was found in the experiments with the diaphragm preparation but not in the experiments with the levator ani muscle. Insulin was found to cause a flux of water from the extracellular to the intracellular compartments in the diaphragm but not in the levator ani muscle. The results are discussed and it is concluded that the intact levator ani preparation is very suitable for further experiments concerning the mechanism of action of insulin.