Chronic-intermittent cold stress in rats induces selective ovarian insulin resistance

Abstract

In rat ovary chronic cold stress increases sympathetic nerve activity, modifies follicular development, and initiates a polycystic condition. To see whether there is a relationship between the previously described changes in follicular development and metabolic changes similar to those in women with polycystic ovary, we have studied the effect of chronic cold stress(4°Cfor 3 h/day, Monday to Friday, for 4 wk) on insulin sensitivity and the effect of insulin on sympathetic ovarian activity. Although cold stressed rats ate more than the controls, they did not gain more weight. Insulin sensitivity, determined by hyperinsulinemic euglycemic clamp, was significantly increased in the stressed animals. Insulin in vitro increased the basal release of norepi- nephrine from the ovaries of control rats but not from those of stressed rats, suggesting a local neural resistance to insulin in stressed rats. The levels of mRNA and protein for IRS1 and SLC2A4(also known as GLUT4), molecules involved in