# 초대배양한 신장 근위세뇨관세포에서 estradiol-17β와 IGF-I 수용체 발현과의 상관관계

• Han, Ho-jae (College of Veterinary Medicine, Chonnam National University) ;
• Nam, Seong-ahn (College of Veterinary Medicine, Chonnam National University) ;
• Park, Kwon-moo (College of Veterinary Medicine, Chonnam National University)
• 한호재 (전남대학교 수의과대학, 호르몬연구센터) ;
• 남성안 (전남대학교 수의과대학, 호르몬연구센터) ;
• 박권무 (전남대학교 수의과대학, 호르몬연구센터)
The mechanisms of $estradiol-17{\beta}$ regulating growth of both normal and neoplastic cells are not clear until now. In studies using various estrogen-dependent breast cell lines, it is recently known that estrogen controls the cell growth by regulating the expression of growth factors and/or their receptors. In the present study, we investigated the effects of $estradiol-17{\beta}$on cell growth and IGF-I binding sites using primary cultured renal proximal tubule cells. We have obtained results as follows : $Estradiol-17{\beta}(10^{-9})$ has stimulatory effects in cell growth. Cotreatment of $estradiol-17{\beta}(10^{-9}M)$ and $IGF-I(5{\times}10^{-8}M)$ significantly increased the growth of primary rabbit renal proximal tubule cells compared to that of $estradiol-17{\beta}$ or IGF-I alone treated cells. In binding studies, we found that the binding of $^{125}IGF-I$ on cell membranes was incubation time- and temperature-dependent. Incubation at $37^{\circ}C$ results in higher binding of $^{125}IGF-I$ than that of $23^{\circ}C$ or $4^{\circ}C$. Maximum binding was observed at $37^{\circ}C$ between 30 and 60 minutes. The binding of $^{125}IGF-I$ to both control and $estradiol-17{\beta}-treated$ cells was inhibited by unlabelled $IGF-I(10^{-8}{\sim}10^{-12}M)$ in a concentration-dependent manner. However, EGF did not compete for $^{125}IGF-I$ binding at $10^{-8}{\sim}10^{-12}M$. IGF-I binding to the membranes from both control and $estradiol-17{\beta}-treated$ cells was also analyzed. We found that $estradiol-17{\beta}-treated$ cells exhibited higher binding activity for IGF-I. When $estradiol-17{\beta}$ or tamoxifen alone, or $estradiol-17{\beta}$ and tamoxifen cotreated cells were compared, the binding ratio of $^{125}I-IGF-I$ of $estradiol-17{\beta}-treated$ cell was significantly increased but was similar to control in both $estradiol-17{\beta}$ and tamoxifen cotreated cell. These results suggest that $estradiol-17{\beta}$ in part controls cell proliferation by regulating the expression of IGF-I receptors in primary rabbit renal proximal tubule cells.