Effect of chronic administration of 17 beta-estradiol on the vasopressor responses induced by the sympathetic nervous system in insulin resistance rats

Several studies have demonstrated that the underlying mechanism of insulin resistance (IR) is linked with developing diseases like diabetes mellitus, hypertension, metabolic syndrome, and polycystic ovary syndrome. In turn, the dysfunction of female gonadal hormones (especially 17 beta-estradiol) may be related to the development of IR complications since different studies have shown that 17 beta-estradiol has a cardioprotector and vasorelaxant effect. This study aimed was to determine the effect of the 17 beta-estradiol administration in insulin-resistant rats and its effects on cardiovascular responses in pithed rats. Thus, the vasopressor responses are induced by sym-pathetic stimulation or i.v. bolus injections of noradrenaline (alpha 1/2), methoxamine (alpha 1), and UK 14,304 (alpha 2) adrenergic agonist were determined in female pithed rats with fructose-induced insulin resistance or control rats treated with: 1) 17 beta-estradiol or 2) its vehicle (oil) for 5 weeks. Thus, 17 beta-estradiol decreased heart rate, pre-vented the increase of blood pressure induced by ovariectomy, but with the opposite effect on sham-operated rats; and decreased vasopressor responses induced by i.v. bolus injections of noradrenaline on sham-operated (control and fructose group) and ovariectomized (control) rats, and those induced by i.v. bolus injections of methoxamine (alpha 1 adrenergic agonist). Overall, these results suggest 17 beta-estradiol has a cardioprotective effect, and its effect on vasopressor responses could be mediated mainly by the alpha 1 adrenergic receptor. In contrast, IR with ovariectomy 17 beta-estradiol decreases or loses its cardioprotector effect, this could suggest a possible link between the adrenergic receptors and the insulin pathway.