Species differences in expression of angiotensin II receptors and angiotensin-converting enzyme in human, canine and rat mitral valve leaflets

In normal valvular collagen turnover in the rat, angiotensin (Ang) II and a ngiotensin-converting enzyme (ACE) seem to be involved. In common human and canine valvular diseases, changes in valvular collagen play a pathogenetic role and the valvular renin-angiotensin system is therefore of particular interest in these species. Healthy mitral valve leaflets and adjacent left ventricular myocardium were taken from five rats and five dogs immediately after euthanasia, and from five humans at autopsy. The valvular and myocard ial Ang II receptors and ACE were detected and measured by quantitative aut oradiography. In rat valves, high levels of Ang II receptors and ACE were f ound. In human and canine valves, insignificant levels were found. Signific ant myocardial levels of Ang II receptors and ACE were found only in the ra t. The study demonstrated major species differences regarding the level of valvular and myocardial Ang II receptors and ACE in man, dog and rat. The l ack of valvular Ang II receptors and ACE in man and dog, suggest that the r enin-angiotensin system plays a minor, if any, role in the physiological va lvular collagen formation in these two species. The findings in humans, how ever, need to be confirmed using fresh material. (C) 1999 Elsevier Science Inc. AII rights reserved.