Presence and localization of a 30-kDa basic fibroblast growth factor-like protein in rodent testes

We have used a recently characterized rabbit antiserum against
basic fibroblast growth factor (bFGF), which recognizes various
forms of bFGF, to examine the presence and localization of bFGF in
the testes of adult rats and mice and the 5-day-old rat. In Western
blots of testicular homogenates of adult rats and mice and immature
rats, immunoreactive single bands at approximately 30 kDa were
detected. Immunocytochemistry revealed specific staining restricted
to the tubular compartment. In 5-day-old rat testes,
prespermatogonia were immunoreactive. The cytoplasm of pachytene
spermatocytes was heavily stained in the adult testes of both
species. Staining of these cells became evident around stage IV/V,
was prominent in stage VII through IX and declined about stage
XII/XIII (rat) or X-XI (mouse). Staining was seen in type A
spermatogonia and in elongating spermatids in their cytoplasmatic
lobes and along their flagellae. Sertoli cells were unstained. We
propose that the pluripotential growth factor bFGF could be
involved in the regulation of germ cell proliferation and
differentiation in the adult and immature testis.