Determination of hormones inducing oocyte maturation in Chalcalburnus tarichi (Pallas, 1811)

Abstract

Chalcalburnus tarichi is an endemic cyprinid species living in the Lake Van basin, in eastern Anatolia, Turkey. The present study was undertaken to determine which hormones induce oocyte maturation in C. tarichi. The levels of 17alpha,20beta,21-trihydroxyprogesterone (20beta-S), progesterone (P), 17alpha-hydroxyprogesterone (17alpha-HOP), 11-deoxycortisol (11-DOC), and 17alpha-hydroxy-20beta-dihydroprogesterone (17,20beta-P) were measured in fish caught from Lake Van and the Karasu River, and injected with human chorionic hormone (hCG) (1,000 and 1,500 IU/kg). Oocytes of fish caught from the lake were also incubated in vitro with different doses (50, 200, and 1,000 ng/ml) of 20beta-S, 17alpha-HOP, 11-DOC, and 17,20beta-P. 11-DOC was found to be the most effective hormone among those measured for inducing oocyte maturation in vivo and in vitro. 17,20beta-P could not be determined in the plasma of any fish in vivo (P < 0.05). 1,000 IU/kg dose of hCG given by injection caused a statistically significant increase in all plasma hormone levels (P < 0.05). It was found that there was a significant decrease in the P level only at 1,500 IU/kg dose of hCG injected (P < 0.05), while the level of other hormones increased at this dose (P < 0.05). It was also determined that all the hormones were effective in germinal vesicle breakdown (GVBD) in in vitro oocyte culture (P < 0.05). However, 11-DOC was found to be the most effective hormone in GVBD at a dose of 200 ng/ml (70% GVBD). In conclusion, 11-DOC synthesized during final oocyte maturation in C. tarichi was found to be a potent inducer of GVBD, which shows that 11-DOC may be described as an oocyte maturation steroid in this species.

Human follicular fluid shows diverse metabolic profiles at different follicle developmental stages

“…In addition, DOC can stimulate Gn release, promote the development of follicles, and induce LH surges to ovulate [28]. DOC was discovered to effectively induce GVBD at all concentrations, and regulates the final oocyte maturational stages in fish [29,30]. These two metabolites are associated with the sensitivity of the body to Gn and could be used as prediction indices for Gn.…”

Synthesis of 17,20β,21‐trihydroxypregn‐4‐en‐3‐one by ovaries of reproductively mature Atlantic cod Gadus morhua

“…Although 17,21‐P has long been known to induce in vitro FOM in fishes (Colombo et al , 1973; Sundararaj et al , 1985; Scott & Canario, 1987), it has never shown to be as effective as 17,20β‐P or 17,20β,21‐P (Canario & Scott, 1988; Thomas & Das, 1997), except in the most primitive of the species that have been tested, A. transmontanus (Webb et al , 2000). There has been a recent claim that 17,21‐P is the MIS in a cyprinid, Alburnus tarichi (Güldenstädt) (Unal et al , 2008). This study, however, did not test the effect of 17,20β,21‐P, but of its 20β,21‐diacetate (which would almost certainly have been inactive).…”

Maturation Inducing Hormones in teleosts: Are progestogens always the first to be nominated?

“…Despite all the information listed above, there exists some fish species with minimal or no increases in the plasma concentrations of either or both of the so-called progestogens during FOM (Alvarado et al, 2015;Roche et al, 2018;Ünal et al, 2008). Furthermore, in vivo or in vitro assays might sometimes contradict with regards to the nomination of progestogens as MIHs.…”