Influence of norepinephrine and exercise on lipolysis in adipose tissue of diabetic rats.

The lipolytic effect of norepinephrine (NE) in adipose tissue in vitro was studied before and after exercise in non-fasted rats with severe, untreated streptozotocin diabetes. It was observed that: 1. NE in increasing concentrations stimulated glycerol release in vitro to an equal extent from the adipose tissue of nondiabetic and diabetic rats. However, the re-esterification of free fatty acids (FFA) in adipose tissue in vitro was decreased by NE in diabetic rats as compared to normal rats. 2. During exercise NE further decreased the re-esterification of FFA in vitro in adipose tissue of diabetic rats. 3. Exercise did not change NE-induced glycerol release in vitro in the adipose tissue of diabetic rats. 4. In diabetic animals the increase in plasma glycerol and FFA during exercise was correlated inversely with the NE-induced release of glycerol and FFA from the adipose tissue of the same animals after exercise. The lipolytic effect of NE is not significantly different in adipose tissue of diabetic and nondiabetic rats. By decreasing the re-esterification of FFA in vitro, NE is probably responsible for the observed increase in the release of FFA in vivo, a likely energy source in severely diabetic animals.