K(ATP) channels and pancreatic islet blood flow in anesthetized rats: increased blood flow induced by potassium channel openers.

K(ATP) channels are important for insulin secretion and depolarization of vascular smooth muscle. In view of the importance of drugs affecting K(ATP) channels in the treatment of diabetes, we investigated the effects of these channels on splanchnic blood perfusion in general and pancreatic islet blood flow in particular. We treated anesthetized Sprague-Dawley rats with the K(ATP) channel openers diazoxide or NNC 55-0118 or the K(ATP) channel closer glipizide. Both diazoxide and NNC 55-0118 dose-dependently increased total pancreatic and islet blood flow in the presence of moderate hyperglycemia, but had no effects on the blood perfusion of other splanchnic organs. Diazoxide markedly lowered the mean arterial blood pressure and thus increased vascular conductance in all organs studied. NNC 55-0118 had much smaller effects on the blood pressure. Glipizide did not affect total pancreatic blood flow, but decreased islet blood flow by 50% in the presence of hypoglycemia. We conclude that K(ATP) channels actively participate in the blood flow regulation of the pancreatic islets and that substances affecting such channels may also influence islet blood flow.