Concentration of Serum Progesterone and Cortisol during Estrous Cycle and Early Pregnancy in Mares

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  • ウマの性周期ならびに妊娠初期における血中プロゲステロンとコルチゾールの消長について
  • ウマ ノ セイシュウキ ナラビニ ニンシンキ ニ オケル ケッチュウ プロゲス

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Abstract

The serum concentration of progesterone and cortisol was determined by radioimmunoassay in the normal 22 mares (9 Percherons and 13 Bretons). Blood samples were collected by jugular venipuncture at 10 AM from all mares every other day during estrus, and every 2 day during luteal phase and early gestation period. Progesterone levels during pregnancy were compared with those during estrous cycles. The progesterone levels for the first 12 days of pregnancy increased almost similarily to those for the 12 day of estrous cycle in the non-pregnant mares, but were still maintained even after the 15-18 days of pregnancy, while levels of the cyclic mares declined rapidly. In the non-pregnant mares, the average concentration of serum cortisol on the day of ovulation was 50.9±13.7(Mean±S.D.) ng/ml, and two peaks were observed at 6 days before ovulation, 109.7±28.2ng/ml and at 18 days after ovulation, 111.9±55.3ngfml. The highest concentration of cortisol in the pregnant mares, 61.9±18.6ng/ml was observed at 18 days after ovulation, and the lowest, 24.2±14.7ng/ml was at 6 days before ovulation. A cyclic pattern was observed for cortisol in the non-pregnant mares with peaks appeared at the beginning of estrus.

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