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(Hypertension. 1999;34:920-923.)
© 1999 American Heart Association, Inc.

Scientific Contributions

Gender Differences in Hypertension in Spontaneously Hypertensive Rats

Role of Androgens and Androgen Receptor

Jane F. Reckelhoff; Huimin Zhang; Kumud Srivastava; Joey P. Granger

From the Department of Physiology and Biophysics, The Center for Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson, Miss.

Correspondence to Jane F. Reckelhoff, PhD, Associate Professor, Physiology and Biophysics, University of Mississippi Medical Center, 2500 N State St, Jackson, MS 39216-4505. E-mail JReckelhoff{at}physiology.umsmed.edu

Abstract—Males are at greater risk of cardiovascular and renal disease than are females. For example, male spontaneously hypertensive rats (SHR) have higher blood pressures than females. Androgens have been strongly implicated in the hypertension of male SHR, because castration attenuates the hypertension. This study determined whether the androgen receptor plays a role in hypertension in male SHR and whether testosterone alone can cause the hypertension or whether conversion to dihydrotestosterone is necessary. Male SHR, aged 10 weeks, were given the androgen receptor antagonist flutamide (8 mg/kg SC; n=8) or the 5-reductase inhibitor finasteride (30 mg · kg^-1 · d^-1 SC; n=11) daily for 5 to 6 weeks. Control rats (n=10) received vehicle (20% benzyl benzoate or ethanol in castor oil). After 5 to 6 weeks, blood pressure (mean arterial pressure) and glomerular filtration rate were measured. Long-term flutamide treatment caused a reduction in mean arterial pressure (control 178±5 mm Hg; flutamide 159±3 mm Hg; P<0.01), but finasteride had no effect (180±5 mm Hg). There were no differences in glomerular filtration rate among the groups. These data indicate that hypertension in male SHR is mediated via the androgen receptor and does not require conversion of testosterone to dihydrotestosterone.

Key Words: flutamide • finasteride • blood pressure • gender