Effects of delapril hydrochloride on the myocardium of spontaneously hypertensive rats.
OBJECTIVE
To investigate the effects of long term treatment with delapril hydrochloride (an angiotensin-converting enzyme inhibitor) on myocardial contractility and ventricular myosin isoenzymes in spontaneously hypertensive rats (SHR).


METHODS
Delapril hydrochloride (10 mg/kg/day by mouth) was administered to 22- to 24-week-old male SHR for eight to 10 weeks. The isometric contractions of isolated left ventricular papillary muscles were observed while being perfused with Tyrode's solution (32 degrees C, pH 7.4, bubbled with 95% oxygen: 5% carbon dioxide, stimulation frequency 0.2 Hz). The left ventricular myosin isoenzymes were separated using pyrophosphate-gel electrophoresis.


RESULTS
The mean systolic blood pressure of the delapril-treated group was significantly lower than that of the untreated control group. The mean ventricular weight was also lower in the delapril-treated than control group (mean +/- SD, untreated: 211 +/- 11 mmHg, n = 6; delapril-treated: 183 +/- 14 mmHg, n = 8, P < 0.01). The mean isometric developed tension (T) and +/-dT/dtmax of isolated left ventricular papillary muscles from the delapril-treated and untreated SHR did not differ significantly. The left ventricular myosin isoenzyme pattern obtained by pyrophosphate-gel electrophoresis, however, showed a significant shift towards VM-1 after long term delapril treatment.


CONCLUSIONS
Long term treatment of SHR with delapril hydrochloride reduced blood pressure, which was associated with regression of cardiac hypertrophy, and changed the ventricular myosin isoenzyme pattern without significantly affecting myocardial contractility.
Takeda
N
N
Department of Internal Medicine, Aoto Hospital, Jikei University School of Medicine, Tokyo, Japan.
Iwai
T
T
Tanamura
A
A
Nakamura
I
I
Nagano
M
M
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology; D007189:Indans / Q000494:pharmacology / Q000627:therapeutic use*; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR
D000806:Angiotensin-Converting Enzyme Inhibitors; D007189:Indans; D007527:Isoenzymes; D009218:Myosins; C047759:delapril