Antihypertensive responses of vasoactive androgens in an in vivo experimental model of preeclampsia.
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Dehydroepiandrosterone (DHEA), testosterone (TES) and its 5-reduced metabolites induce a nongenomic vasorelaxation in several vascular beds of mammals; similarly these hormones produce systemic hypotensive and antihypertensive responses in normotensive and hypertensive male rats. Thus, it was hypothesized that the antihypertensive response of androgens, whose levels are elevated during gestation, protect against gestational hypertension. An animal model of preeclampsia was induced in female Wistar rats using DOCA-salt-treated pregnant (PT) and normal pregnant (NP) rats. In vivo experiments in conscious rats revealed that bolus intravenous injections of DHEA, TES, 5- or 5-dihydrotestosterone (-DHT) log -1.0 to 2.0molk-1min-1, produced substantial transient reductions in arterial blood pressure (BP), without significant changes in heart rate (HR). Mean arterial blood pressure (MAP) was reduced significantly in both groups. PT rats were more sensitive to the antihypertensive responses of androgens than NP. DHEA and 5-DHT were the most potent to reduce MAP: 6607 and 692.0mmHg in PT but only 330.5 and 351.2mmHg in NP rats, respectively. In isolated aortas of PT and NP, the concentration-response curves to each androgen (0.1-100M) indicated that KCl-induced pre-contraction is more sensitive to all androgens than phenylephrine (Phe) pre-contractions. Notably, 5-DHT is the greatest vasorelaxant with KCl-induced contraction than with Phe contraction of both groups, suggesting a preferential blockade on L-VOCCs. TES exhibited minor vasorelaxing effect of aortas pre-contracted with KCl, compared to its precursor DHEA and its 5-reduced metabolites. These data show that these androgens exert acute vasorelaxing effects in vitro and remarkably, reduce the BP in vivo in PT and NP at term pregnancy. Moreover, a deficit in feto-placental androgen production during pregnancy may trigger the development of preeclampsia or gestational hypertension.