NITRENDIPINE IMPROVES GLUCOSE-TOLERANCE AND DEOXYGLUCOSE UPTAKE IN HYPERTENSIVE RATS

We assessed the effect of the vasodilating calcium channel blocker nit rendipine on glucose tolerance in young spontaneously hypertensive rat s (SHR) (n = 15). The nitrendipine group received 1 g/kg chow for 3 we eks. Untreated SHR (n = 14) served as controls. At 3 weeks body weight was comparable, whereas systolic blood pressure was 157+/-9 mm Hg in nitrendipine-treated rats versus 191+/-10 mm Hg in controls (mean+/-SD , P<.00001). Fasting glucose was 6.8+/-2.7 mmol/L in nitrendipine-trea ted versus 8.9+/-1.5 mmol/L in control rats (P<.03). An intravenous gl ucose tolerance test (300 mg/kg) showed plasma glucose levels at 2, 5, 15, and 30 minutes to be significantly lower in the nitrendipine-trea ted group versus controls (two-way ANOVA, P<.03). Glucose utilization was estimated by the uptake of [H-3]deoxyglucose after its intravenous administration (2 mu Ci/100 g body wt) to instrumented awake animals. Heart and striated muscle uptake was, respectively, 7983+/-5812 and 9 51+/-731 cpm . mu L/ g min in the nitrendipine-treated group versus 35 32+/-2316 and 424+/-201 cpm . mu L/g min in controls (P<.02 and P<.04, respectively). [H-3]Deoxyglucose plasma half-life and fasting and pos t-glucose load insulin levels were comparable in the two groups. The r esults show that nitrendipine improves glucose tolerance by increasing muscle glucose uptake. We suggest that glucose tolerance in SHR is in fluenced by muscle blood flow and can be improved by vasodilation.