Disruption of the secretion and action of 17,20 beta-dihydroxy-4-pregnen-3-one in response to a rise in temperature in the Arctic charr, Salvelinus alpinus. Consequences on oocyte maturation and ovulation
2011
Gillet, Christian | Breton, Bernard | Mikolajczyk, Tomasz | Bodinier, Pascal | Fostier, Alexis,
Plasma levels of 17,20β-dihydroxy-4-pregnen-3-one (17,20βP), and the timing of ovulation were investigated in female Arctic charr (Salvelinus alpinus) reared at 5 °C and at 10 °C during the pre-spawning period. The effects of switching from 5 to 10 °C, and from 10 to 5 °C were also investigated. 17,20βP plasma levels were higher at 5 °C than at 10 °C. A switch from 10 to 5 °C stimulated 17,20βP secretion, whereas a switch from 5 to 10 °C had the opposite effect. Ovulation occurred spontaneously in the females kept at 5 °C, and in those switched from 10 to 5 °C. In contrast, ovulation was inhibited in females reared at 10 °C, and in those switched from 5 to 10 °C. Oocyte maturation at 5 °C and at 10 °C in the presence of LH or of 17,20βP was also investigated in vitro using donor females reared at 5 or 10 °C. Both LH and 17,20βP stimulated oocyte maturation more effectively in oocytes incubated at 5 °C than at 10 °C. At both incubation temperatures, the rearing temperature of the donor females had a significant impact on their responsiveness to LH stimulation, but had no effect on their responsiveness to 17,20βP stimulation. In addition to the inhibition of LH secretion, which had already been reported, the results reported here show that in Arctic charr raising the temperature above the physiological range reduces both follicular responsiveness to LH stimulation and the sensitivity of oocytes to 17,20βP stimulation.
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