Differentiation-related changes in the distribution of glycoconjugates in rat testis.

The distribution of glycoconjugates in differentiating rat testis was investigated by fluorescein labeled lectins during embryogenesis and postnatal development. Double immunofluorescence with rhodamine coupled laminin antibodies was used to delineate testicular cords from the interstitium in embryonic testes. Rat testis was found to be rich in various glycoconjugates, with distinct differentiation-related changes in their distribution. All types of germ cells contained carbohydrate rich compounds in their cytoplasm. Glycosylation in the embryonic testis was different from that in the adult rat. At an early stage of testicular differentiation, the labeling of germ cells and other testicular cells was almost identical. The lectin binding patterns of embryonic germ cells and somatic cells were related to the developmental age of the animal, with a graded disappearance of galactose containing glycoconjugates in embryonal spermatogonia. Spermatogenic cell differentiation was characterized by striking changes in lectin binding patterns of germ cells, particularly in the acrosomes of developing spermatids, in relation to their functional activation and the emergence of adult type of glycosylation during the postnatal maturation of the testis. As the knowledge of regular glycosylation throughout tissue differentiation is of significance for the analysis of aberrant glycosylations occurring in pathologic disorders, our findings suggest the usefulness of lectin histochemistry for the studies on germ cell differentiation.