Blood pressure response to hyperinsulinemia in salt-sensitive and salt-resistant rats

Abstract

We investigated the role of insulin in salt-sensitive hypertension in Dahl salt-sensitive and salt-resistant rats. The rats were kept in metabolic cages, and sodium intake and urinary sodium excretion were measured In salt-sensitive rats receiving a 0.3% NaCl diet, sodium retention was significantly greater at weeks 1 and 2 in rats that received an insulin infusion than in those receiving a saline infusion Mean arterial blood pressure and plasma norepinephrine levels were significantly higher at week 3 in insulin-treated rats than in saline-treated rats (mean arterial pressure, 137 ± 3 mm Hg versus 119 ± 3 mm Hg, p<0.05; plasma norepinephrine, 0.40±0.02 ng/ml versus 0.27±0.01 ng ml, p<0.05). Insulin did not influence sodium retention, mean arterial pressure, or plasma norepmephrine in salt-resistant rats. Coadminbtration of an α-blocker (bunazosin, 10 mg/kg per day for 3 weeks) in salet-sensitive rats abolished the insulin-induced elevations in mean artenal pressure and sodium retention. When salt-sensitive rats were fed a low salt diet (0.03% NaCl), insulin did not raise mean artenal pressure. Thus insulin elevated blood pressure only in the salt-sensitive model. The sympathetic nervous system and sodium retention in the early phase of insulin overload may contribute to elevation of mean artenal pressure in this model.