H. Fujinaga et al., FSH AND LH UP-REGULATE EPIDERMAL GROWTH-FACTOR RECEPTORS IN RAT GRANULOSA-CELLS, Journal of Endocrinology, 140(2), 1994, pp. 171-177
Epidermal growth factor (EGF) modulates ovarian folliculogenesis and s
teroidogenesis and its binding sites have been demonstrated in the ova
ry. We investigated the localization of EGF-binding sites in the rat o
vary, and the effects of FSH and LH on EGF binding to cultured granulo
sa cells. Autoradiographic localization of I-125-labelled mouse EGF-bi
nding sites was demonstrated in the granulosa and luteal cells. Displa
cement study and Scatchard analysis showed that a single class of spec
ific binding sites for I-125-labelled mouse EGF was present in the gra
nulosa cells, obtained from the ovaries of immature rats treated with
diethylstilboesterol. The number of binding sites and the apparent dis
sociation constant were 4336 binding sites/cell and 3.42 pmol/l respec
tively. The granulosa cells were cultured for 48 h at 37-degrees-C in
medium alone or with increasing amounts of ovine FSH (oFSH; 1-1000 mug
/l). FSH treatment increased I-125-labelled mouse EGF binding to the g
ranulosa cells in a dose-dependent manner. After culture with oFSH (10
0 mug/l) for 48 h, the cells were cultured in medium alone or with inc
reasing amounts of ovine LH (oLH; 1-1000 mug/l) for an additional 48 h
. LH treatment also increased I-125-labelled mouse EGF binding in a do
se-dependent manner, compared with the control. However, neither FSH n
or LH altered receptor-binding affinity. Furthermore, after culture wi
th oFSH (FSH-primed) or oFSH followed by oLH (LH-primed), tissue plasm
inogen activator (tPA) activities in the conditioned media were examin
ed by fibrin autography. FSH-primed or LH-primed granulosa cells were
more responsive to EGF action to induce an increase in tPA activity. I
n conclusion, it is suggested that functional receptors for EGF in rat
granulosa cells are up-regulated by FSH and LH.