Terbutaline decreases the blood flow of the pancreatic islets but does not reduce the diabetogenic action of streptozotocin in the rat.

Male Sprague-Dawley rats were injected i.v. with either 0.5 ml saline or terbutaline (1 mg/kg body weight) and 5 min later the whole pancreatic blood flow (PBF) and the islet blood flow (IBF) were measured with a microsphere technique. Injection of terbutaline increased the serum insulin concentrations, but had no effect on the serum glucose concentration of the animals. The IBF was decreased by terbutaline by approximately 40%, while the PBF remained unchanged. Furthermore, the diabetogenic action of streptozotocin (SZ; 35 mg/kg bodyweight; i.v.) was not affected by the administration of terbutaline 5 min before the SZ injection. It is concluded that the beta 2-selective adrenoceptor agonist terbutaline selectively decreases the blood flow of the pancreatic islets in spite of its stimulatory effects on the release of insulin. This confirms our previous findings that the IBF and the release of insulin can be dissociated. Moreover, the hyperglycemic action of a single diabetogenic dose of SZ could not be reduced by terbutaline administration despite the reduction in the IBF. This suggests that a decrease in the islet blood flow is not sufficient to prevent the cytotoxicity of SZ.