Insulin sensitivity and glucose effectiveness estimated by the minimal model technique in spontaneously hypertensive and normal rats

This study was performed to compare glucose metabolism in anaesthetised spo ntaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) in an attemp t to clarify whether this animal model of hypertension approximates the ins ulin-resistant state seen in human hypertension. With this aim the minimal model of glucose kinetics was applied to glucose and insulin data derived f rom a 12-sample, 120 min intravenous glucose tolerance test (IVGTT) perform ed in ten SHR and nine WKY rats under pentobarbital anaesthesia. This metho d provided two metabolic indices: the glucose effectiveness, S-G, which qua ntifies the ability of glucose per se to enhance its rate of disappearance and to inhibit hepatic glucose production, and the insulin sensitivity, S-I , which measures the ability of insulin to enhance plasma glucose disappear ance and to inhibit hepatic glucose production. Systolic and diastolic arte rial pressures in the SHR group were significantly higher (P < 0.0005) than in the WKY group. Mean S-G and S-I estimates from the SHR group (S-G = 16. 2 (+/- 2.0) x 10(-2) dl min(-1) kg(-1) and S-I = 12.5 (+/- 1.9) x 10(-4) dl min(-1) kg(-1) (<mu>U ml(-1))(-1)) were not significantly different (P > 0 .05) from mean estimates that characterised the WKY group (S-G = 13.1 (+/- 1.5) x 10(-2) dl min(-1) kg(-1) and S-I = 15.8 (+/- 4.3)x 10(-4) dl min(-1) kg(-1) (muU m(-1))(-1)). This result is in contrast with reported findings from humans in which insulin sensitivity is significantly reduced in the p resence of hypertension.