Captopril improves hypertension and cardiomyopathy in rats with pheochromocytoma

Cellular mechanisms of captopril-induced matrix remodeling in Syrian hamster cardiomyopathy

BACKGROUND

Although angiotensin-converting enzyme (ACE) inhibitors have become a mainstay of treatment for chronic congestive heart failure (CHF), it is not known whether the cardiac remodeling effects are a secondary phenomenon, resulting from ACE inhibitors' hemodynamic actions of afterload reduction, or occur through an independent mechanism.

METHODS AND RESULTS

We used ultrasonic tissue characterization to define potentially salutary effects of treatment with ACE inhibitors on the material properties of the heart and its potential influence on cardiac remodeling at the cellular level. Ten 1-month-old, cardiomyopathic (CM) Syrian hamsters and 6 normal (NL) hamsters were treated with captopril (2 g/L water ad libitum), and 10 CM hamsters and 10 NL hamsters were maintained untreated for 3 months. Hearts were excised, and backscattered radiofrequency data were acquired from 1200 independent sites from each specimen with a high-resolution 50-MHz acoustic microscope for calculation of integrated backscatter (IB). Treatment with captopril reduced left ventricular mass, calcium concentration, and IB in CM hearts without affecting myofiber size or collagen concentration. The IB from grossly normal regions of myocardium in NL hamsters, treated CM hamsters, and untreated CM hamsters was not significantly different. The IB from the microscopic regions of scar tissue in treated CM hamsters was significantly less (P = .0004) than that from scar tissue in untreated CM hamsters.

CONCLUSIONS

The reduced IB from treated scar tissue components reflects specific alterations in the material properties (elastic stiffness, density) of fibrous regions in CM hearts induced by captopril. This is the first report that defines specific cellular effects of ACE inhibitors on the material properties of isolated components of cardiac tissue in experimental cardiomyopathy. These alterations in material properties of scar tissue components represent a potential mechanism for the salutary actions of ACE inhibitors in heart failure.

Rapid reversal of heart failure in a patient with phaeochromocytoma and catecholamine-induced cardiomyopathy who was treated with captopril

A patient with a phaeochromocytoma and severe left ventricular heart failure caused by a catecholamine-induced cardiomyopathy is described. The clinical signs of congestive heart failure resolved rapidly on treatment with captopril and myocardial performance became normal within two weeks of medical treatment with captopril for one week and with captopril in combination with phenoxybenzamine for another week.

Comparative effects of antihypertensives on proteinuria: angiotensin-converting enzyme inhibitor versus alpha 1-antagonist

Control of hypertension improves the course of renal disease. We compared the renal hemodynamic and permselective responses to an angiotensin-converting enzyme inhibitor (CEI) (enalapril) and an alpha 1-antagonist (prazosin) in 14 patients with established glomerular disease. A single-blinded, randomized, cross-over design was used consisting of a 3-week baseline period followed by two 4-week treatment periods, which were separated by a 4-week washout period. During the treatment periods, the CEI or alpha 1-antagonist was added to the patients' baseline antihypertensive medications. Mean arterial pressure (MAP) was reduced to similar levels by both drugs, although the time-averaged blood pressure throughout the study was higher with the alpha 1-antagonist. Twenty-four-hour urinary protein, albumin, and IgG excretion were not significantly different at the end of the CEI and alpha 1-antagonist periods. However, compared with baseline values, significant decreases in total protein and IgG excretion occurred only during the CEI period, while albumin excretion decreased with both drugs. A 22% decrease in the fractional clearance of albumin (4.95 +/- 1.44 to 3.88 +/- 1.57 x 10(-3); P less than 0.01) and a 49% decrease in the fractional clearance of IgG (1.58 +/- 0.42 to 0.81 +/- 0.28 x 10(-3); P less than 0.001) occurred during CEI therapy with no significant changes in these parameters being seen with alpha 1-antagonist therapy (albumin: 4.95 +/- 1.44 to 4.48 +/- 1.51 x 10(-3), P = NS; IgG: 1.58 +/- 0.42 to 1.71 +/- 0.70 x 10(-3), P = NS). At the time of the fractional clearance measurements, MAP proved to be lower on the CEI. Reanalysis of the data for the subgroup of 11 patients without differences in MAP during the clearance period demonstrated a beneficial effect favoring CEI. Except for the greatest decreases in blood pressure (21 to 30 mm Hg), a greater antiproteinuric effect for a given decrease in blood pressure was seen with the CEI. Additionally, reduction in proteinuria occurred in a subset of seven patients whose baseline MAP was in the normotensive range. In conclusion, lowering MAP improves proteinuria. CEI appears to exert a more favourable effect even at similar MAP. Reductions in blood pressure, even within the accepted normal range, lessen permselective defects.