Ovarian androstenedione production is enhanced by insulin during the period of delayed ovulation in a vespertilionid bat, Scotophilus heathi.

The aim of the present study was to evaluate the role of insulin in the production of high concentrations of androstenedione in the ovary of Scotophilus heathi during the period of delayed ovulation. The concentrations of serum insulin were found to be high during November and December and declined significantly before ovulation. A significant correlation was observed between circulating insulin concentration and body weight as well as with serum androstenedione concentrations. Autoradiographic study demonstrated specific accumulation of 125I-labelled insulin in the ovarian thecal and interstitial cells. Insulin increased both basal and hCG-stimulated androstenedione production by the ovary in vitro during November. These results indicate that insulin may be involved in inducing high androstenedione synthesis by the ovary and thus may be indirectly responsible for inducing delayed ovulation in S. heathi.