Relationship between blood pressure, plasma insulin and triglyceride concentration, and insulin action in spontaneous hypertensive and Wistar-Kyoto rats. Previous results have shown that spontaneously hypertensive rats (SHR) are insulin resistant, hyperinsulinemic, and hypertriglyceridemic as compared to Wistar-Kyoto rats (WKY). Since SHR rats also have higher blood pressures than WKY rats, the current study was initiated in an attempt to evaluate the relationship between the magnitude of blood pressure and the differences in insulin and lipid metabolism seen in SHR and WKY rats. The experimental variables to be compared were determined in three groups of SHR and WKY rats, varying in age: Group I rats were 6 to 7 weeks of age; Group II rats were 8 to 9 weeks old; whereas Group III rats were 12 to 13 weeks of age. Maximal insulin-stimulated glucose transport by adipocytes isolated from SHR rats was significantly lower (P less than .005) than isolated adipocytes from WKY rats in all three groups, whereas plasma insulin and triglyceride concentrations were significantly higher (P less than .005). Blood pressure was also higher in SHR than in WKY rats within each group. Since absolute values for maximal insulin-stimulated glucose uptake did not change statistically as the rats grew older, the magnitude of the decrease in SHR rats was similar in each group. The increase in plasma insulin and triglyceride concentration observed in SHR rats was also the same in each group, but the absolute values increased with age in both SHR and WKY rats. However, blood pressure rose significantly with age in SHR, but not WKY rats, leading to a progressive increase in the degree of hypertension in SHR rats. These results support the view that hypertension, per se, does not lead to insulin resistance, hyperinsulinemia, and hypertriglyceridemia. 