Results The presence of heparin in the vas deferens fluid, resulting from the intra testicular injection, affected the spermatozoa remaining under such conditions for 2 hours by inducing a statistically significant (P< 0.01) decrease in their motility (Table 1), as compared with the spermatozoa obtained from the other vas deferens (communicating with the testis to which only saline was injected) and from vasa deferentia of the control mice. The observed changes were permanent, ie persisted during the incubation of spermatozoa in PBS for at least 120 min in vitro, following the removal of heparin from the environment of spermatozoa. Discussion

Heparin has been detected in various vertebrate tissues, where it can effect a number of different physiological processes at the cellular level (JAQUES 1979; VESTRATE 1984). Heparin is also present in the female reproductive system of mammals (TADANO & YAMADA 1978; FOLEY et al. 1978; MILLER & AX 1990), in which it can also exert an effect on spermatozoa. Heparin binds to the spermatozoan cell membrane in a highly specific process similar to the receptor-mediated hormone attachment. The effectiveness of this binding depends on some surrounding fluid (DELGADO et al. 1982). After attachment to the plasmalemmal receptors, heparin is permanently bound to the cell membrane, but a subsequent transport to the cytoplasm has not been observed. Thus, heparin influences the cytophysiological processes by altering the transport properties and enzymatic activities of the cell membrane (JAQUES 1979). Specific interaction of heparin with the cell membrane brings about various changes in the structure and physiology of spermatozoa, ie the decondensation of the nuclear chromatin observed in human spermatozoa (DELGADO et al. 1980) or initiation of