LOCALIZATION OF INTEGRIN BETA-1, ALPHA-1, ALPHA-5, AND ALPHA-9 SUBUNITS IN THE RAT TESTIS

Very late activation (VLA, beta(1); alpha(1); alpha(5), alpha(9)) inte grins were studied by immunoblotting and immunohistochemistry in the t estes of sexually mature rats. AU integrin subunits were present in me mbrane fractions of homogenized testes. Immunohistochemistry revealed that tile anti beta 1 antibody recognized peritubular cells and the ba sement membrane of blood vessels. Immunoreactivity was also demonstrat ed in the lamina propria, basement membrane, and the basal cytoplasm o f Sertoli cells. In elongating spermatids, beta 1 integrin was localiz ed to the acrosome. The alpha(1) subunit was expressed in peritubular cells and in the lamina propria. In the adluminal compartment, round s permatids were stained diffusely for the alpha(1) subunit. Immunoreact ivity for alpha(1) integrin was found additionally in the acrosomes of elongating spermatids shortly before their release into the seminifer ous tubule lumen. The alpha(5) subunit was expressed in the acrosomes of elongating spermatids as well as in their distal cytoplasm during s tages III-VI; the cytoplasmic lobes of elongate spermatids and/or resi dual bodies also appeared to be immunostained in seminiferous tubules at stages VII-VIII. The alpha 9 subunit was immunolocalized only in th e basement membrane and in peritubular cells. These data suggest that integrins are involved in spermatogenesis, in particular ill the proce ss of spermatid maturation.