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The aim of the present study was to develop an in vitro system for short time conservation of ovarian follicles in Sterlet sturgeon (Acipenser ruthenus). In this study in vitro effect of 17α, 20β- Dihydroxyprogesterone (DHP) on the oocyte maturation of Sterlet was studied to develop a method for estimating the physiological state of oocytes to select the breeders capable of producing high quality gametes after hormonal stimulation. The oocytes were cultivated in Ringer solution (RMS) and L-15 medium supplemented with 20% FBS, Streptomycin sulphate, Penicillin G potassium and Amphotericine B in the presence of DHP at 1μg/ml (group 1) and 2 μg/ml (group 2) concentrations or absence the DHP (control group) for 12, 16 and 20 hr. In this study the effect of 15% and 20% FBS, as well as temperatures 16°C and 18°C were examined. After 12, 16 and 20 hr., polarization index (PI) of 30 ovary follicles from each group measured to determine GV position. The cells of cultivated oocytes did not proliferate in Ringer solution but they proliferated in L-15 very well. After fourteen days, confluent monolayer of propagated cells formatted on the bottom surface of culture vessel. Mean polarity index (PI) of oocytes in control groups and groups 1 and 2 in fish 1, 2 and 3 after 12 hours was (0.13 ± 0.007, 0.12 ± 0.006, 0.11 ± 0.007); (0.109 ± 0.007, 0.108 ± 0.006, 0.106 ± 0.007); (0.10 ± 0.005, 0.09 ± 0.005, 0.11 ± 0.006); after 16 hours was (0.098 ± 0.007, 0.102 ± 0.006, 0.064 ± 0.004); (0.108 ± 0.007, 0.095 ± 0.004, 0.056 ± 0.003); (0.11 ± 0.007, 0.092 ± 0.006, 0.06 ± 0.004) and after 20 hours was (0.097 ± 0.007, 0.063 ± 0.006, 0.069 ± 0.009); (0.097 ± 0.007, 0.063 ± 0.006, 0.069 ± 0.009); (0.113 ± 0.005, 0.056 ± 0.005, 0.070 ± 0.004), respectively. The minimum mean oocyte PI observed after 16 hr. incubation of the follicles with 2μg/ml and 20 hr. with 1μg/ml concentration of DHP. It was not observed maturation (GVBD) in oocytes. With the successful cultivation of ovarian follicles of Sterlet sturgeon, it can be applied as an in vitro model for different purposes, such as monitoring of the physiological and developmental state of ovarian follicles, studying the hormonal stimulation of oocyte maturation and the effects of different factors on the physiological state of ovarian follicles in order to develop a criterion for the selection of suitable females to aid breeding. Key words: Sterlet sturgeon, Acipenser ruthenus, oocyte, in vitro
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