Levels of Some Ovarian Hormones in the Pre- and Post Spawning Periods of Chalcalburnus tarichi Pallas, 1811, and the Postovulatory Structure of Follicles


Abstract: The structure of postovulatory follicles and the levels of ovarian 11-dehydrocorticosterone (11-DHC), estradiol-17\beta (E_2), 17\alpha-hydroxyprogesterone (17\alpha -OH-P), and progesterone (P), before and after spawning, were studied in Chalcalburnus tarichi. It was observed that postovulatory follicles are characterized by a highly vascular thecal layer and hypertrophied granulosa cells containing dense smooth endoplasmic reticulum, many large mitochondria with tubular cristae, and lipid droplets. Ovary 11-DHC level was low in the pre- and post-spawning periods (38.3 ± 4.9-22.3 ± 2.6 ng/ml). The level of E_2 was 216.8 ± 31.1 ng/ml before spawning. This hormone declined on the 1^{st} and 5^{th} day after spawning and increased again to the level of 216.8 ± 6.7 ng/ml on the 10^{th} day; however, the E_2 level decreased significantly on the 15^{th} day (61.5 ± 17.8 ng/ml) (P < 0.01). The 17\alpha -OH-P level was low (84.5 ± 49.4 ng/ml) before spawning and reached a peak (295.7 ± 52.5 ng/ml) on the 10^{th} postspawning day, but a slight decline was observed on the 15^{th} day (190 ± 21.5 ng/ml) (P > 0.01). The P level was low (23.4 ± 18.3 ng/ml) before spawning. Its level began to increase after spawning and reached a peak on the 10^{th} postspawning day (200.7 ± 29.1 ng/ml) (P < 0.01), but declined significantly on the 15^{th} day (63.2 ± 19.5 ng/ml) (P < 0.01). The results obtained from this study indicate that: a) In the postovulatory follicles, the granulosa cells produce steroids; b) 11-DHC has no effect before or after spawning; c) E_2 induces spawning; d) 17\alpha -OH-P and P have an effect after spawning. It can be concluded that the apoptotic cells in postovulatory follicles increased on the 15^{th} day, at which time E_2 and P hormones were at their lowest levels after spawning in C. tarichi.

Keywords: Chalcalburnus tarichi, postovulatory follicle, ovarian steroids

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