IMMUNOHISTOCHEMICAL STUDY OF SEMINIFEROUS EPITHELIUM IN ADULT BOVINE TESTIS USING MONOCLONAL-ANTIBODIES AGAINST KI-67 PROTEIN AND PROLIFERATING CELL NUCLEAR ANTIGEN (PCNA)

The distribution pattern of proliferating cell nuclear antigen (PCNA) and Ki-67 protein was studied in adult bovine seminiferous epithelium by means of immunohistochemistry using monoclonal antibodies. Tailorin g the methodological protocol for each of the two proliferation marker s was a necessary prerequisite for obtaining optimal results in tubula r sections and whole-mounts. A-, I- and B-spermatogonia displayed PCNA -positive nuclei, except during meta-, ana- and telophases of mitosis. PCNA-negative nuclei in the basal tubular compartment, excluding thos e from non-cycling Sertoli cells, belonged to the spermatogonia precur sor cell line. However, only about 30%, 45% and 47% of the respective A-, I-, B-spermatogonia had positive nuclei after exposure to the MIB- 1 antibody directed against the Ki-67 protein. Spermatogonia with MIB- 1-negative nuclei represented cells in the G(1)-phase. Both antibodies reacted intensely with the nuclei of preleptotene primary spermatocyt es. PCNA reactivity was also present during leptotene through pachyten e. Ki-67 protein expression was absent during leptotene and zygotene b ut was again encountered during pachytene and meiosis I and II. Anti-P CNA/anti-protein gene product 9.5 double-labelling indicated that the transition from spermatogonia precursor cells into A(1)-spermatogonia is not strictly synchronized in a given tubular segment, a possible re ason for the flexibility in A-spermatogonial propagation seen in bovin e seminiferous tubules.