Testosterone modulates vasodilation in mesenteric arteries of hypertensive rats

Aims: To evaluate the effects of testosterone on endothelium-dependent vasodilation and oxidative stress in mesenteric resistance arteries.

Main methods: Spontaneously hypertensive rats (SHR), aged 8 to 10 weeks, were divided into four groups: intact (SHAM), intact treated with testosterone (TTO; 3 mg/kg/day) via subcutaneous route (s.c.), intact treated with testosterone and anastrozole [aromatase enzyme inhibitor (TTO + ANA; 0.1 mg/kg/day, s.c.)] and intact treated with testosterone and finasteride [5 α-reductase enzyme inhibitor (TTO + FIN; 5 mg/kg/day, s.c.)] for four weeks. Concentration-response curves to acetylcholine (ACh, 0.1 nmol/L - 10 μmol/L) were obtained in mesenteric resistance arteries previously contracted with phenylephrine (PE, 3 μmol/L), before and after the use of selective inhibitors. Reactive oxygen species (ROS) levels were assessed in the vessels and the endothelium analyzed by scanning electron microscopy.

Key findings: TTO group showed a lower participation of nitric oxide (NO), increased oxidative stress, and participation of prostanoids and endothelium-dependent hyperpolarization (EDH), possibly to maintain the vasodilator response. Lower participation of NO and prostanoids, combined to an increased participation of EDH, were observed in the TTO + ANA group, in addition to higher levels of ROS and altered endothelial morphology. The vasodilation to ACh was impaired in TTO + FIN, along increased participation of NO, reduction of prostanoids, and greater EDH-dependent vasodilation.

Significance: Testosterone contributes to endothelial vasodilation by enhancing EDH through an increased participation of epoxyeicosatrienoic acids. While the decrease in NO appears to involve the participation of dihydrotestosterone, 17 β-estradiol seems to stimulate the action of the NO pathway and prostanoids.