Vanadyl sulfate lowers plasma insulin and blood pressure in spontaneously hypertensive rats

Spontaneously hypertensive rats (SHR) are hyperinsulinemic compared with their Wistar-Kyoto (WKY) controls. Since previous studies have demonstrated that vanadyl sulfate lowers insulin levels in nondiabetic rats, we used vanadyl to explore the relation between hyperinsulinemia and hypertension. In a prevention study, 5-week-old SHR and WKY rats were started on long-term vanadyl sulfate treatment. Vanadyl in doses of 0.4 to 0.6 mmol/kg per day lowered plasma insulin (252 +/- 22.8 versus 336 +/- 12.6 pmol/L, treated versus untreated, P < .01) and systolic blood pressure (158 +/- 2 versus 189 +/- 1 mm Hg, P < .001) in SHR without causing any change in plasma glucose. No changes were seen in the treated WKY rats. At 11 weeks of age, a group of untreated rats from the prevention study was started on vanadyl treatment as before. Again, vanadyl caused significant and sustained decreases in plasma insulin (264 +/- 12.6 versus 342 +/- 6.6 pmol/L, treated versus untreated, P < .001) and blood pressure (161 +/- 1 versus 188 +/- 1 mm Hg, P < .001) in SHR but had no effect in the normotensive WKY controls. Furthermore, restoration of plasma insulin in the vanadyl-treated SHR to pretreatment levels (subcutaneous insulin, 14,000 pmol/kg per day) reversed the effects of vanadyl on blood pressure (vanadyl with insulin, 190 +/- 3.0 mm Hg versus vanadyl without insulin, 152 +/- 3.0 mm Hg, P < .001). Since vanadyl treatment resulted in decreased weight gain, treated SHR were compared with a corresponding pair-fed group.(ABSTRACT TRUNCATED AT 250 WORDS)