EFFECTS OF EXERCISE TRAINING ON INSULIN-RESPONSE TO INTRAVENOUS GLUCOSE IN PUBERTAL RATS

This study was undertaken to evaluate the effects of exercise training on glucose tolerance and glucose-stimulated insulin response (GSIR) in 55- and 90-day-old peripubertal female rats. Intravenous glucose tolerance tests (0.5 g/kg) were done in: 1) 90-day-old rats exercised in swimming sessions for either 5 or 10 weeks and evaluated 48 h after the last exercise bout; 2) 55-day-old rats exercised for 5 weeks and evaluated either 24 h or 48 h after the last exercise bout and; 3) unexercised 55- and 90-day-old rats. The total area under the GSIR curve was suppressed in 55- and 90-day-old rats exercised since the age of 21 days. However, this decrease was obsered 48 and only 24 h after the last exercise bout in the 90- and 55-day-old rats respectively. Exercise did not affect the GSIR curve for the 90-day-old rats subjected to 5 weeks of exercise training (started at 55 days of age) when evaluated 48 h after the last exercise bout. Nor did one single bout of swimming exercise (2 h) in the last 24 h affect the GSIR in unexercised 55-day-old rats. These results suggest that the shorter duration of the residual effects of exercise in the younger rats (55 days) was related to the shorter length of the training programme. Body weight was not significantly reduced with exercise in 55-day-old rats, whereas the same amount of exercise in 90-day-old rats caused body weight reduction of approximately 35 g (p < 0.05). It is concluded that exercise training before and during puberty in female rats, is associated with a decline in glucose-stimulated insulin concentrations.