title: Long-term alpha 1 blockade does not reverse cardiac hypertrophy in spontaneously hypertensive rats.
abstract: Not all antihypertensive drugs induce regression of left ventricular (LV) hypertrophy in hypertension, although they may equally lower blood pressure. The effects of alpha 1-blockers on regression have been inconsistent. In this study, bunazosin, a selective alpha 1-blocker, (15 mg/kg/day in food) was given to male spontaneously hypertensive rats (SHR) from 15 to 35 weeks of age to evaluate its effects on cardiac hypertrophy, hemodynamics, and neurohumoral factors. Age- and sex-matched SHR served as controls. LV function and cardiac output were determined by a micromanometer and thermodilution, respectively. Bunazosin significantly decreased blood pressure in conscious rats (from 209 to 192 mmHg, p < 0.01) but did not reduce LV mass. Heart rate, LV end-diastolic pressure, dp/dtmax, and cardiac output were similar in the 2 groups. Plasma renin activity was unaltered but plasma norepinephrine levels were higher in the treated rats (p < 0.05). Thus, bunazosin produced a significant relative reduction of blood pressure but did not reverse LV hypertrophy in SHR. Inadequate afterload reduction (8%) due to severe hypertension (> 200 mmHg) may explain the absence of regression. The rise of plasma norepinephrine levels may also offset the beneficial effects of bunazosin.
authors.affiliation: Third Department of Internal Medicine, Osaka Medical College, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nishimura
authors.forename: J
authors.initials: J
authors.lastname: Kubota
authors.forename: M
authors.initials: M
authors.lastname: Okabe
authors.forename: M
authors.initials: M
authors.lastname: Ueyama
authors.forename: T
authors.initials: T
authors.lastname: Oka
authors.forename: K
authors.initials: K
authors.lastname: Kawamura
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage* / Q000494:pharmacology; D000818:Animals; D006439:Hemodynamics / Q000187:drug effects; D006973:Hypertension / Q000150:complications*; D017379:Hypertrophy, Left Ventricular / Q000188:drug therapy*; D008297:Male; D009638:Norepinephrine / Q000097:blood; D011799:Quinazolines / Q000008:administration & dosage* / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D012083:Renin / Q000097:blood
chemical_list: D000317:Adrenergic alpha-Antagonists; D011799:Quinazolines; C018176:bunazosin; D012083:Renin; D009638:Norepinephrine