Effect of ageing on insulin and insulin-glucose sensitivity tests in rats.

Insulin tolerance tests have shown old rats to respond to injection of the hormone by a sharp and lasting drop in blood sugar. The difference between these animals and young and adult ones lies in their inability to restore a normal blood glucose level. Glucose tolerance and insulin-glucose tolerance tests show that glucose uptake under the influence of the hormone is significantly reduced with age in absolute terms. However, the difference in glucose assimilation coefficient in the absence or presence of insulin (deltaK) is comparable in all age groups; thus senile rats were found to be as sensitive even to small doses of hormone as the adult ones, if basal levels are taken into account.