Increased Coronary Reactivity and Endothelial Dysfunction in Young Cardiomyopathic Hamsters.

Abstract

Previous data by our group indicated the presence of vascular dysfunction in the aorta of 2‐month‐old cardiomyopathic (CM) hamsters (Bio‐T02 strain). To determine the status of coronary resistance (CR) in these animals, isolated hearts from control (CT) and CM of 1, 2, and 6 months of age were studied using a Langendorff setup. At 1, 2, and 6 months of age, CR (mmHg × mL / min × g, RU) in CT was 1.11 ± 0.39, 1.79 ± 0.31, and 5.67 ± 2 RU, respectively. These values were similar to those of CM at their respective age groups. Infusion of thromboxane (THX, 0.1 μM) in CT, increased CR by 2.02, 3.58, and 3.78‐fold at 1, 2, and 6 months of age (P≤0.05), respectively. In CM, THX increased CR by 2.51, 4.70, and 5.16‐fold in these age groups (P≤0.05). Bradykinin (1 μM) inhibited the THX‐induced contraction in CT by 91±8%, 57±11%, and 48±7%, whereas in CM this parameter was reduced by 76±3%, 31±10%, and 48±7% at 1, 2, and 6 months of age, respectively (P≤0.05). SNP abolished the THX‐induced contraction to values not different from basal levels in all groups. These findings indicate that the coronary circulation of CM is hyperreactive to THX, an effect that increases as age progresses. The reduced bradykinin induced relaxation in CT and CM indicates the development of endothelial dysfunction, an effect that peaks (≈50%) at 2 months of age in CM. We conclude that coronary dysfunction is present in young CM. Supported by NIH 2S06‐GM 08224.