Effects of insulin and prior exercise on prostaglandin release from perfused rat muscle Evidence that prostaglandins do not mediate changes in glucose uptake

Prostaglandin generation and its inter-relation to the metabolic effects of insulin and prior exercise were examined in perfused muscle of fed rats. During a 60 min perfusion of the rat hindquarter, a substantial release of the prostaglandins PGF2 alpha, PGE2 and 6-oxoPGF1 alpha was observed. Blood cells present in the perfusate released these substances in negligible amounts indicating the prostaglandins were produced by the hindquarter. Addition of insulin to the perfusate increased both glucose uptake and the generation of PGE2 and 6-oxoPGF1 alpha. At 30 min after intense treadmill exercise, glucose and alpha-aminoisobutyric acid (AIB) uptake by the hindquarter were increased in the absence of added insulin, but prostaglandin release was not increased. Insulin further increased glucose and AIB uptake; however, in contrast with its effects in non-exercised rats, insulin no longer stimulated prostaglandin generation. Indomethacin (10 microM) added to the perfusate inhibited the release of PGF2 alpha and PGE2 by 90% and the release of 6-oxoPGF1 alpha by 54%. It had no effect on the stimulation of glucose uptake by either insulin or prior exercise. The data indicate that insulin increases prostaglandin synthesis by perfused rat muscle, and that prior exercise blocks this effect. They suggest that under the conditions studied prostaglandins do not mediate the effects of insulin or prior exercise on glucose uptake.