Orchidectomy attenuates high-salt diet-induced increases in blood pressure, renovascular resistance, and hind limb vascular dysfunction: role of testosterone.

Abstract

Sex hormone-dependent vascular reactivity is an underlying factor contributing to sex differences in salt-dependent hypertension. This study evaluated the role of androgens (testosterone) in high salt-induced increase in blood pressure (BP) and altered vascular reactivity in renal blood flow and perfused hind limb preparation. Weanling male rats (8weeks old, 180-200g) were bilaterally orchidectomised or sham operated with or without testosterone replacement (Sustanon 250, 10mg/kg intramuscularly once in 3weeks) and placed on a normal (0.3%) or high (4.0%) NaCl diet for 6weeks. The high-salt diet (HSD) increased arterial BP, renal vascular resistance (RVR) and positive fluid balance (FB). These changes were accompanied by decreased plasma nitric oxide levels. The increased BP, RVR and FB observed in the rats fed a HSD were reversed by orchidectomy while testosterone replacement prevented the reversal. Phenylephrine (PE)-induced increased vascular resistance in the perfused hind limb vascular bed was enhanced by HSD, the enhanced vascular resistance was prevented by orchidectomy and testosterone replacement reversed orchidectomy effect. Vasorelaxation responses to acetylcholine (ACh) and sodium nitroprusside (SNP) were impaired in HSD groups, orchidectomy attenuated the impairment, while testosterone replacement prevented the orchidectomy attenuation. These data suggested that eNOS-dependent and independently-mediated pathways were equally affected by HSD in vascular function impairment and this effect is testosterone-dependent in male Sprague-Dawley rats.