Effects of long term treatment with an alpha 1 adrenoceptor blocker on cardiac hypertrophy, contractility, and myosin isoenzymes in spontaneously hypertensive rats.
OBJECTIVE
The aim was to investigate the effects of long-term treatment with an alpha 1 blocker, bunazosin hydrochloride, on blood pressure, heart weight, myocardial contractility, and ventricular myosin isoenzyme pattern in spontaneously hypertensive rats (SHR).


METHODS
Bunazosin hydrochloride was given orally in a dose of 10 mg.kg-1.d-1 for 8-9 weeks. Isometric tension development was measured in isolated left ventricular papillary muscles. The left ventricular myosin isoenzyme pattern was determined by pyrophosphate gel electrophoresis.


METHODS
14 male SHR (seven treated and seven untreated rats) aged 23 to 24 weeks were studied.


RESULTS
The blood pressure of the bunazosin treated rats was approximately 14% lower than that of the untreated rats at the end of the treatment period. The ventricular weight of treated SHR was significantly lower (around 8%) than that of untreated rats, but there were no significant differences between the two groups in the mechanical data obtained from isolated left ventricular papillary muscles. The myosin isoenzyme pattern of the left ventricle was significantly shifted toward VM-1 in the bunazosin treated SHR, the VM-1 concentration in the treated group being 38% greater than in the untreated group.


CONCLUSIONS
These results indicate that long term treatment with bunazosin hydrochloride reduces blood pressure and leads to the regression of cardiac hypertrophy in SHR. Myocardial energetics (as represented by the myosin isoenzyme pattern) were affected, but there was no influence on myocardial tension development.
Department of Internal Medicine, Aoto Hospital, Jikei University School of Medicine, Tokyo, Japan.
N
N
Takeda
I
I
Nakamura
T
T
Ohkubo
T
T
Iwai
A
A
Tanamura
M
M
Nagano
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D006321:Heart / Q000033:anatomy & histology / Q000187:drug effects*; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000201:enzymology; D009218:Myosins / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D011799:Quinazolines / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D013997:Time Factors
D000317:Adrenergic alpha-Antagonists; D011799:Quinazolines; C018176:bunazosin; D009218:Myosins