The effect of age on insulin-degrading activity in rat tissue.

Insulin-degrading activity was measured in the 100,000g supernatant fraction of muscle, liver, and kidney from rats of varying ages. Young animals (four weeks old) had the highest activity in all three tissues. By seven weeks of age the activity in both muscle and liver had decreased significantly as compared with four-week-old animals. A slight but nonsignificant decrease occurred in kidney. In animals over one year of age the insulin-degrading activity in all three tissues was significantly less than the activities at either four or seven weeks. In contrast the effect of age on degradation of albumin and parathormone was much less marked.