終於 the end of summer...(the 3rd maniscript)

Testosterone benefits ovarian development by modifying the expressions levels of ovarian VEGF-Flk in Japanese eel (Anguilla japonica) during artificial maturation

abstract
Angiogenesis is essential to the development. Ovarian follicular development is associated with ovarian vascular developments in mammals, and the degeneration of follicular vascular capillaries is the major cause to follicle atresia. VEGF (vascular endothelial growth factor) is the most important factor to ovarian angiogenesis, two VEGF receptors, Flt and Flk, have been identified. VEGF is conserved from fishes to mammals. A commercial scale of artificial eel (Anguilla japonica) seed production is not well established, an abnormal physiological status provoked by artificial hormonal manipulations is suggested. We proposed an abnormality on ovarian angiogenesis in the exogenous hormones stimulated eel. Testosterone (T) has been showed to stimulate and enhance the survival and synchronous development of eel ovary. Our aims were to investigate the correlation between ovarian development and VEGF-Flk expressions by CPE and T on ovarian VEGF-Flk expressions. Eel were treated with CPE or T supplement weekly for 9 weeks. RT-PCR and histoimmunochemistry were employed to test the levels of ovarian VEGF-Flk. Our data showed that ovarian expressions levels of VEGF were stimulated first then the expressions levels decreased by CPE; ovarian expressions levels of Flk were inhibited by CPE. Anyways, a negative correlation between ovarian development (GSI) and ovarian VEGF-Flk expressions were observed, but ovarian vasculatures have developed, the increase of ovarian podocalyxin (Podo, a specific surface marker for vascular endothelia) expressions supported this hypothesis. By contrast, the supplement of T (CPT+T) for 9 weeks increased GSI, rescued the decrease of ovarian VEGF-Flk expressions, and stimulated ovarian Podo expressions as compared with 9 weeks of CPE alone. We can not deny the possibility that the eel used for the manipulation were at the pre-silver stage, the exogenous hormones treatments leaded the abnormal ovarian angiogenesis. Our results may provide a base to ameliorate the hormonal treatment regime during the eel artificial maturation procedure.