Insulin increases blood flow rate in the microvasculature of cremaster muscle of the anesthetized rats.

: The hemodynamic actions of insulin in skeletal muscle microvasculature are not yet well elucidated. In the present study, we investigated the effects of systemic insulin injection on arteriole and capillary diameter and blood flow rate in rat cremaster muscle, using intravital real-time confocal laser-scanning microscope system in combination with selective fluorescent labeling. Subcutaneous insulin injecbon (1 U/kg) significantly increased serum insulin levels at 15 minutes as compared with saline injection. At 15 and 30 minutes after insulin injection, blood glucose levels were significantly lower compared to saline injected controls. Arteriolar diameter was significantly increased at 15 and 30 minutes by insulin. Arteriolar erythrocyte flow velocity was significantly increased at 15 and 30 minutes. In addition, capillary erythrocyte flow velocity was increased at 15 and 30 minutes. These results demonstrated that calculated blood flow rates in capillary and arteriole increased after insulin injection.