The aim of this study was to examine alterations in skeletal muscle microvascular hemodynamics occurring one week after the onset of streptozotocin diabetes. Diabetes was induced in 9 male, Sprague-Dawley rats by intraperitoneal streptozotocin (60 mg/kg); 10 age-matched rats acted as controls. The animals were then studied 6-8 days after the induction of diabetes. For study of skeletal muscle microvascular hemodynamics the right cremaster muscle was exteriorized. Vessel diameters were measured with an image shearing monitor and red blood cell velocity was determined with an optical Doppler velocimeter. Measurements were taken in the resting and dilated (adenosine applied topically to the muscle) states. In the resting state, diabetic rats showed significant enlargement of venules less than 120 microM, while arteriolar diameters were comparable to those of controls. The extent of dilation in response to adenosine was significantly decreased in both the arterioles and venules of the diabetic animals. Blood flow through the main arteriole supplying the tissue was significantly decreased in the diabetic animals in both the resting and dilated states. The results of this study demonstrate changes in skeletal muscle hemodynamics after one week of streptozotocin diabetes. The diabetic animals are characterized by decreased perfusion and diminished ability to lower vascular resistance by vasodilation.