Effects of enalapril on human sperm motility

The angiotensin converting enzyme inhibitor, enalapril, reduced the motility of washed human spermatozoa. The concentrations producing 50% inhibition were: (percentage motility) 11.6 +/- 2.6 mM, (average forward velocity) 8.0 +/- 1.5 mM and (motility index) 8.5 +/- 2.1 mM (mean + s.e.m.). Enalapril 20 mM prevented all forward movement and reduced percentage motility to an extremely low level. Motility was reduced within 20 sec of addition and little further change occurred during a 60-min incubation period. Inhibition of percentage motility by enalapril was reversible with a 5-min washing procedure following a 5-min incubation period, but not following a 60-min incubation period. Enalapril 20 mM did not impair plasma membrane integrity (hypoosmotic swelling test) or viability (nigrosin-eosin stain). It is concluded that the antimotility effects of enalapril are not caused by inhibition of angiotensin converting enzyme, but may be of interest in the search for new spermicidal agents.