Abstract: 336

IMMUNOCYTOCHEMICAL LOCALIZATION OF L-SELECTIN IN RAT TESTIS AND SPERMATOZOA.

Ann-Marie Broome^{1 *}, Clarke F. Millette¹
University of South Carolina, School of Medicine, Columbia, SC 29208 ¹

Selectins are cell adhesion molecules involved in leucocyte homing. Previously thought limited to the vasculature, we have recently demonstrated expression and functioning of L-selectin in the testis [Broome and Millette 1997,1998]. In these earlier studies, we identified L-selectin on Sertoli cell plasma membranes. L-selectin was not, however, detected on the surfaces of early-to-mid spermatogenic cells using Western blotting, immunofluorescence, RT-PCR or ELISA protocols. Here, we report immunocytochemical localization of testicular selectin. Using antibodies specific for either the extracellular or cytoplasmic domain of L-selectin (Santa Cruz Biochemicals), labeling in sectioned rat testis is detected on membranes surrounding all differentiating germ cells up to early condensing spermatids. Reaction product is not detected in the cytoplasm of these cells. We interpret these findings to confirm our prior biochemical determinations of L-selectin expression on Sertoli cell surfaces. Surprisingly, however, early condensing spermatids exhibit intense cytoplasmic staining for L-selectin. Label is retained throughout spermiogenesis. Accordingly, we have initiated studies examining expression of L-selectin by rat sperm. Immunofluorescent data reveal L-selectin on the convex anterior surfaces of the rat sperm head. Preliminary ultrastructural immunogold studies suggest that selectin is on the plasma membrane, not acrosomal membranes. Ongoing experiments are designed to confirm this localization by using SEM and by investigating acrosome-reacted spermatozoa. Our results suggest that sperm L-selectin could play a role in epididymal maturation, interactions with epithelia of the female reproductive tract, or recognition of the oocyte. (Supported by HD-15269; USCSM RDF)

    This abstract is being presented on Monday, August 2 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.