LOCALIZATION OF FIBROBLAST GROWTH-FACTOR-2 (FGF-2) PROTEIN AND THE RECEPTORS FGFR-1-4 IN NORMAL HUMAN SEMINIFEROUS EPITHELIUM

Fibroblast growth factor 2 (FGF-2), which occurs in various isoforms b oth species and tissue specifically, regulates cell proliferation and differentiation via a dual receptor system consisting of heparan sulph ate proteoglycans and receptor tyrosine kinases (FGFRs). This study de monstrates for the first time the distribution pattern of FGF-2 and th e receptors FGFR 1-4 in the normal seminiferous epithelium of adult me n. In western blot analyses, the polyclonal antibody, anti-FGF-2, show s two immunoreactive bands at 18 and 24 kDa. On paraffin sections, pos itive immunoreaction occurs within the cytoplasm of spermatogonia. The distribution pattern of the polyclonal anti-FGFR 1-4 antibodies is as follows: anti-FGFR-1 (one 68-kDa band) stains nuclei and cytoplasm of spermatogonia; anti-FGFR-3 (five bands at 68, 78, 105, 125 and 145 kD a) stains the nuclei of all germ cells except those of elongated sperm atids; and anti-FGFR-4 (one 48-kDa band) stains the cytoplasm of prima ry pachytene spermatocytes. We were unable to demonstrate FGFR-2 immun oreactivity either in western blot analysis or on paraffin sections. T his distribution pattern suggests that FGF-2 in spermatogonia is invol ved in the autocrine and paracrine regulation of the proliferation and differentiation of spermatogonia and spermatocytes via the receptors FGFR-1, FGFR-3 and FGFR-4.