RELATION OF GLYCOSYLATED HEMOGLOBIN TO IN-VIVO CARDIAC-FUNCTION IN RESPONSE TO DOBUTAMINE IN SPONTANEOUSLY DIABETIC BB WOR RATS

The contribution of metabolic control to in vivo myocardial contractil e function in response to beta(1)-adrenergic stimulation was determine d in the spontaneously diabetic BB Wor rat. The study involved a group of insulin-dependent BB Wor rats showing marked variations in metabol ic control, assessed by the level of glycosylated hemoglobin (gHb). Th ese diabetic BB rats were divided into moderate and severe (%gHb > 14) diabetic groups. A group of Wistar rats and diabetes-resistant BB Wor rats served as controls. In vivo myocardial contractile function was measured under basal conditions and after i.v. dobutamine infusions in anesthetized rats, using a catheter-tip pressure transducer inserted into the left ventricle. No dramatic differences in heart rate with do butamine stimulation were observed between the moderate, severe diabet ic, and diabetes-resistant groups. However, heart rate was lower in Wi star control rats compared with these groups. Systolic left ventricula r pressure was depressed in severe diabetic rats compared with Wistar controls. In addition, positive dP/dt was significantly less in the se vere diabetic group at the highest doses of stimulation, whereas negat ive dP/dt was depressed under basal conditions and remained so with in creasing doses of dobutamine. In the diabetic group maximal systolic l eft ventricular pressure, rate-pressure product, and negative dP/dt re sponses to dobutamine were all inversely correlated with gHb. These re sults indicate that changes in metabolic control of the insulin-depend ent BB diabetic rat can contribute to a depressed myocardial contracti le function.