The Influence of Cortisol Level on Progesterone and Ovulation in the Estrus Dogs

혈액 내 코티졸의 패턴 변화가 발정 암캐의 P4 변화와 배란에 미치는 영향

It is generally accepted that chronic stress impairs female reproduction. It negatively affects ovarian function and the number of ovulated oocytes. Chronic stress lowers the number of retrieved oocytes. Ovarian follicular development is regulated by both pituitary-derived gonadotropins and intraovarian regulatory factors. The main corticosteroids are cortisol, cortisone, 11-deoxycortisol and corticosterone, cortisol being one of the most commonly used welfare and stress physiological indicator. In this study, we investigated the effect of cortisol level on progesterone patterns and ovulation in the dog. Cortisol and progesterone level of serum were analyzed by radioimmunoassay. The day of ovulation was considered as the day when serum progesterone concentration was 6.0~8.0 ng/ml. In vivo dog oocytes were collected by flushing oviducts of mixed-breed bitches at three days after ovulation. We classified dogs as having group 1 (cortisol level, 0 ${\leq}$ or < $2{\mu}g/dl$), group 2 (corisol level, 2 ${\leq}$ or < $4{\mu}g/dl$), group 3 (cortisol level, 4 ${\leq}$ or < $6{\mu}g/dl$) and group 4 (cortisol level, $6{\mu}g/dl$ ${\leq}$). The patterns of progesterone were not different in four cortisol groups. The average numbers of retrieved oocytes was not different in four cortisol groups. These results suggest that different cortisol levels on estrus dogs do not affect ovulation, number of ovulated oocytes and progesterone changes.