Hypogonadal Hypertension in Male Sprague‐Dawley Rats Is Reversed by Testosterone Replacement Therapy, which Suppresses Renin‐Angiotensin System Expression

Abstract

Testosterone (TES) and other androgens are efficacious vasodilators acutely, both in vitro and in vivo; however, their long‐term effects on arterial blood pressure (BP) are unclear. We previously reported that castration (CsX) produced hypertension in normal male rats, and that TES replacement therapy (TRT) was antihypertensive and normalized BP. Thus, long‐term effects of endogenous TES and exogenous TRT on BP and renin‐angiotensin system (RAS) function were studied in intact (InT) and castrated (CsX) male Sprague‐Dawley (SD) and Testicular‐feminized male (Tfm, androgen receptor defective) rats (12–13 wk old). Weekly measurements of systolic BP (tail cuff plethysmography) revealed a progressive rise in BP over 10 wks in CsX (108 ± 0.9 vs. 139 ± 1.2 mmHg), while BP remained stable in InT (109 ± 3.1 vs. 115 ± 0.5). During the next 5 weeks, half of CsX received TRT (CsX+TES‐enanthate‐replaced; 1.75 mg/kg, 2X/wk). BP gradually declined to normal in CsX+TES replaced rats (115 ± 1.2), while BP remained elevated in CsX (141 ± 1.2) and normal in InT (113 ± 0.3). In separate CsX‐SD rats, treatment with Losartan (LST; 250 mg/L drinking water) prevented development of hypertension at 10 wks (95 ± 0.8 CsX+LST vs. 139 ± 1.2 in CsX). During the next 5 weeks with TRT, BP declined in CsX+TES (113 ± 1.3) and remained lower in CsX+LST (99 ± 0.4). In Tfm, CsX resulted in a similar rise in BP (108 ± 0.6 vs. 139 ± 0.4 mmHg), and TRT reduced BP to a similar extent (106 ± 1.5). Real‐time PCR (rt‐PCR) of kidney from InT, CsX, and CsX+TES rats revealed that CsX increased expression of renin (45.5%), AT1 receptor (AT1R; 38%), and angiotensin converting enzyme (ACE; 239%) mRNA, while TRT normalized expression of renin, AT1R, and ACE mRNA to levels of InT rats. In contrast, CsX reduced expression of angiotensinogen (Angt) mRNA (59%) while TRT restored Angt mRNA to 78% of InT rats. 24 hr urine output (UO) in InT‐SD was 48.3 ml/kg at baseline, 34.3 at 10 wks, 38.4 at 12 wks, and 34.8 at 15 wks. UO in CsX‐SD was 47.6, 30.3, 25.2, and 27.7; UO in CsX+TRT was 46.1, 29.2 36.2, and 29.5. These data suggest that: 1) endogenous androgens (TES) exert antihypertensive effects in male SD and Tfm rats; 2) the antihypertensive effect of TES appear to involve a diuretic effect on the kidney, which is non‐genomically mediated; and 3) these antihypertensive effects may involve TES‐induced reductions in RAS expression in the kidney.Support or Funding InformationState of TexasThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.