Effects of Adrenergic Drugs on Isolated and Perfused Hearts of Streptozotocin-Induced Diabetic Rats
1987 Volume 44 Issue 3 Pages 233-240
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1987 Volume 44 Issue 3 Pages 233-240
To examine the myocardial contractile response of the diabetic heart, effects of isoproterenol (ISO) and norepinephrine (NE) on perfused hearts isolated from streptozotocin (STZ)-induced diabetic rats and insulin-treated diabetic rats were evaluated. Male Sprague-Dawley rats, weighing 200-260 g, were divided into the control (C)-group, diabetes mellitus (DM)-group and diabetes mellitus treated with insulin (DMI)-group. The C group was injected with buffered vehicle. DM and DMI groups were injected intravenously with 60 mg/kg STZ on the first day. Three days after STZ injection, the DMI group was subsequently treated with 4 U of Lente insulin subcutaneously every day. At 45 days after injection of STZ, experiments were performed using a Langendorff perfused heart preparation. The heart was paced at 300 beats/min, and myocardial developed tension (T) was measured isometrically. Plasma glucose values (mg/dl) were 142.4±8.7 in C, 499.3±15.6 in DM and 370.6±27.6 in DMI group. The order of percent increase in T induced by ISO (3×10-9-3×10-8g) was C=DMI>>DM, and that by NE (10-7-10-6g) was C>DMI>DM. On the other hand, the percent increase in T induced by CaC12 (1.1 ×10-4-2.2×10-3g) and aminophylline (AMI, 0.31×10-3-5.00 ×10-3g) was not significantly different among three groups. These results indicate that adrenergic receptor-mediated contractile response was significantly depressed in the diabetic heart.
