Coronary Hemodynamics in Diabetic Spontaneously Hypertensive Rats

Abstract

We investigated the coronary hemodynamics in conscious spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats 4 and 20 weeks after Streptozotocin or vehicle injection. The hemodynamic parameters were measured at rest and during maximal coronary vasodilation with dipyridamole. Streptozotocin, 40 or 60 mg/kg, produced moderate or severe diabetes in both strains, but resulted in a mortality of 11.3 or 40.8% in SHR alone. The left and right ventricular weights were decreased with no change in their ratios to body weight in both strains. Severely diabetic SHR and WKY revealed hypotension, bradycardia, an increased cardiac index and decreased total peripheral resistance index at both weeks. Moderately diabetic SHR revealed similar changes except for an unaltered cardiac index. Short-term severely diabetic SHR alone displayed an in-creased basal bi-ventricular coronary flow (per u n i t mass). The maximal coronary flow was unaltered i n any group by diabetes. The left ventricular transmural flow distribution was also unaltered i n any group. However, severe diabetes i n SHR diminished a coronary flow reserve (maximal minus basal flow) of the l e f t ventricle a t 4 weeks, and that of both ventricles a t 20 weeks. Thus, the severity and duration of diabetes had a strain-related influence on the systemic and coronary hemodynamics, w i t h deaths and a reduced coronary flow reserve i n SHR alone. The minimal coronary vascular resistance i n both ventricles (per u n i t mass) showed no increase i n each group by diabetes, suggesting no overalldecrease i n functional cross-sectional area of the coronary vasculature.

Key Words:

• Streptozotocin Diabetes
• Spontaneously Hypertensive Rats
• Wistar-Kyoto Rats
• Dipyridamole
• Coronary Flow
• Coronary Vascular Resistance