Fig. 1. Immunohistochemical localization of MT1-MMP in 19-day-old (A,B), 33-day-old (C-F) and 60-day-old (G,H) rat testis. MT1-MMP was uniformly distributed in 19-day-old testis (A) but it concentrated in the apical portions of the seminiferous tubules in 33-day-old testis (C). Late pachytene spermatocytes (E) and early spermatids (F) are intensely stained in 33-day-old rats. In adult rats (G), immunoreactivity differed according to the stages indicated in roman numerals, with sperm cells in stage VIII being the most strongly labeled. Controls in B, D and H show no staining. Bar, 350 µm for A-D,G,H and 110 µm for E,F. Abbreviation: bv, blood vessel.