[Possible involvement of the renin-angiotensin system in reproduction. I. Occurrence and role in the male reproductive tract].

With regard to the blood pressure the regulative function of the renin-angiotensin-system (RAS) is well known. Knowledge of the last years is that components of the RAS are available also in organs and excrets of the male reproductive tract. So, the angiotensin-converting-enzyme (ACE) - a key enzyme of the RAS - exists in the testes in an extraordinary high activity exceeding those of the lung tissue. In the ejaculate this so-called "testicular ACE" is associated with sperms, whereas the seminal plasma contains the higher molecular "pulmonary ACE". Because both isoenzymes posses the same catalytic effectiveness, the occurrence of adequate substrates (angiotensin I, bradykinin) and degrading products as effectors (angiotensin II), respectively, is of high importance for the valuation of the physiological relevance of the RAS in the process of fertility. Up to date, the knowledge is still insufficient, partly even contradictory. Therefore at present the regulative function(s) of the RAS in the male reproductive tract can only be expressed as postulates.