Effect of age and day time on the adenosine modulation of basal and insulin-stimulated glucose transport in rat adipocytes

Abstract

1. 1. The relationship between the activity of adenosine metabolizing enzymes 5′nucleotidase (5′N), adenosine kinase (A.T.) and adenosine deaminase (A.D.) with basal and insulin-stimulated glucose transport in isolated fat cells from young and old animals was studied at 08:00 and 16:00 hr. 2. 2. In cells from young animals a larger insulin-stimulation of glucose transport was observed at 16:00 hr than at 08:00 hr. Also at 16:00 hr small changes in 5′N, A.K. and A.D. activities suggest a decrease in adenosine formation. 3. 3. In the cells from old animals no effect of insulin was observed at any time, while a 3–5-fold increase in 5′N indicated a predominance of adenosine formation at both times studied. 4. 4. An inverse relationship was observed in the changes of adenosine metabolism and insulin action.