Cytochemical and Western blot analysis of the subcompartmentalization of the acrosome in rodents using soybean lectin

In the present study, the formation and development of the acrosome during spermiogenesis in four different rodent species (rat, mouse, hamster and gu inea pig) was compared by means of cytochemical and blotting techniques usi ng a lectin from soybean (SBA). This lectin recognizes specifically the acr osome of the four species at all steps of formation. At the ultrastructural level, SBA-binding pattern was similar in the acrosome of the rat, mouse a nd hamster. SBA preferentially labelled the electron-lucent area of the acr osome in early spermatids (Golgi and cap phases) and the outer region of th e acrosome in mature spermatids (acrosome and maturation phase). The lectin binding pattern was more complex in the guinea pig acrosome. Three differe nt subdomains can be established in the early acrosome of the guinea pig. T he lectin bound the three subdomains but mainly a thin fold which spreads o ver the nucleus during the cap phase. In the acrosome phase, SBA strongly r eacted with the principal segment. In contrast, no reactivity was observed in most of this segment in maturation phase spermatids. In this phase, SBA bound preferentially a thin area covering the dorsal region of the apical s egment. Lectin blots of detergent-extracted testes indicated that SBA only recognizes proteins of high molecular weight (> 100 kD) in the four species studied. The results obtained in the present study suggest that the develo pment of acrosomal subdomains is very similar in the mouse, rat and hamster but shows a more complex pattern in the guinea pig.