Effects of exercise on insulin distribution and action in testosterone-treated oophorectomized female rats

Administration of testosterone (T) to oophorectomized (Ovx) female rats is followed by severe insulin resistance, localized to postreceptor cellular e vents in the muscle. In this study, intervention by exercise was introduced to examine whether circulatory adaptations are involved in insulin resista nce. Two groups of Ovx rats were studied: one group was given T (Ovx+T); an other group had free access to running wheels (Ovx+T+Ex). In addition, one control group (sham operated) was studied. Insulin sensitivity was measured with the euglycemic hyperinsulinemic clamp technique (submaximal) for 150 min. Muscle interstitial glucose and insulin concentrations were measured b y microdialysis. The measurements showed that, in Ovx+T rats, the onset of insulin action was significantly (P < 0.05) slower during the first 95 min of the clamp compared with that in Ovx+T+Ex and controls. Muscle interstiti al concentrations of insulin but not glucose were lower in both Ovx+T and O vx+T+Ex rats than in controls throughout the clamp. It was concluded that p hysical exercise prevented the slow onset of insulin action in Ovx+T rats w ithout changing the distribution time of muscle interstitial insulin. The r esults indicate that hyperandrogenicity is characterized by delayed muscle insulin action. Physical exercise reverses these defects without any benefi cial effect on muscle interstitial insulin concentrations.