No expression of angiotensin II receptors and angiotensin-converting enzyme in myxomatous canine mitral valve leaflets. An autoradiographic study

The renin-angiotensin system, including angiotensin (Ang) II and angiotensi n-converting enzyme (ACE), plays an important role in cardiac fibrous tissu e formation. Since changes in valvular collagen are a central part of myxom atous mitral valve disease in the dog, we speculated that Ang II and ACE mi ght pla! a role in the pathogenesis of this disease. In 10 mitral valves, five with and five without clear myxomatous changes, t hr presence and distribution of Ang II receptors and ACE was examined autor adiographically, using I-125-Ang II and I-125-lisinopril, respectively. At postmortem examination, diseased valves were taken from old dogs, control v alves from young adult dogs. No significant level of Ang II and lisinopril binding was found in normal a s well as diseased valve leaflets. Equally low, insignificant levels of I-1 25-Ang II binding were found in the myocardium of dogs with and without val vular disease. No significant level of myocardial I-125-lisinopril binding was found. The lack of autoradiographic evidence of Ang II receptors and ACF, in norma l and diseased canine mitral valve leaflets suggests that the renin-angiote nsin system does not play a major role in the pathogenesis of the valvular changes.