Seasonal Changes in Luteal Progesterone Concentration and mRNA Expressions of Progesterone Synthesis-related Proteins in the Corpus Luteum of Mares |
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| Authors: | Kozai Keisuke Hojo Takuo Takahashi Masashi Acosta Tomas J Nambo Yasuo Okuda Kiyoshi |
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| Institution: | Laboratory of Reproductive Physiology, Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan. |
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| Abstract: | Although circulating progesterone (P(4)) levels tend to change with the season, little is known about the seasonal changes of P(4) synthesis-related proteins in the corpus luteum (CL) of mares. To examine these changes, seventy-four ovaries containing a CL were collected from Anglo-Norman mares at a local abattoir in Kumamoto, Japan (~N32°), five times during one year. The stages of the CLs were classified as early, mid and regressed by macroscopic observation of the CL and follicles. The mid CL, which had the highest P(4) concentration, was used to evaluate the seasonal changes in P(4) synthesis. The luteal P(4) concentration and mRNA expression of luteinizing hormone receptor (LHCGR) were lowest during early winter and highest during late winter. The mRNA expressions of steroidogenic acute regulatory protein (StAR), P450 cholesterol side-chain cleavage enzyme (P450scc) and 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) were lowest during early winter and increased during late winter. These results suggest that P(4) synthesis in the CL is affected by the seasonal changes in the mRNA expressions of P(4) synthesis-related proteins in mares. |
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