Submitted on November 14, 2006
Accepted on March 1, 2007
Effect of Hypoxia on the Release of Vascular Endothelial Growth Factor and Testosterone in Mouse TM3 Leydig cells
Guey-Shyang Hwang1, Shyi-Wu Wang, Wen-Min Tseng2, Ching-Han Yu2, and Paulus S. Wang3*
1 Department of physiology, National Yang-Ming Universuty, No.155, Sec.2, Li-nong St., Taipei, 112, Taiwan - Republic of China
2 Taipei 11221, Taiwan - Republic of China
3 Department of Physiology, National Yang-Ming University, Shih-Pai, Taipei 11221,Taiwan, 11221
* To whom correspondence should be addressed. E-mail: pswang{at}ym.edu.tw.
Hypoxia has been shown to stimulate the expression of vascular endothelial growth factor (VEGF) which is a major mediator for angiogenesis and vasculogenesis. During hypoxia, VEGF promotes angiogenesis in the testis. However, the effect of VEGF on the steroidogenesis of testosterone and the cell proliferation in Leydig cells is unclear. To assess the effects and the action mechanisms of hypoxia, a mouse TM3 Leydig cell line was employed in the present study. The Leydig cells were incubated in an incubator chamber (95% N2, 5% CO2) for 1-24 hours. The cultured media were collected and assayed by testosterone radioimmunoassay and VEGF enzyme immunoassay. MTT assay was used to detect the proliferation of Leydig cells. The present results showed that the proliferation of Leydig cells was enhanced significantly by hypoxia. The basal VEGF release was increased, and the response of VEGF production to hCG was also enhanced in hypoxic condition. During hypoxia, administration of hCG or VEGF stimulated proliferation of Leydig cells, but the stimulatory effect was abolished by the administration of anti-VEGF antibody. Higher doses of VEGF stimulated testosterone release in a dose dependent manner. Administration of anti-VEGF antibody abolished the stimulatory effect of VEGF on testosterone release. These data suggest that hypoxia stimulates cell proliferation and testosterone release in Leydig cells via an increase of VEGF production.
