Temporal relationships between hormonal concentrations and the electrical resistance of the vaginal tract of blue foxes (Alopex lagopus) at pro-oestrus and oestrus

摘要

Summary. During pro-oestrus, baseline LH concentrations for 9 vixens (pooled data) ranged from 0·8 to 5·3 ng/ml. In each vixen, baseline levels were interrupted by elevations of LH ranging from 3·1 to 10·4 ng/ml. A major preovulatory LH surge was detected in all the vixens. The LH peak ranged from 13·5 to 73·0 ng/ml with an average of 27·8 ± 18·8 (s.d.) ng/ml. Plasma LH concentrations declined to a basal level of 1·3 ± 1·0 ng/ml within 48 h of the peak value. The duration of the LH surge was 1–3 days. The LH peak occurred 1 or 2 days before any sexual receptivity was observed. All the vixens were mated twice 2–5 days after the LH peak; 8 conceived. Plasma concentrations of oestradiol-17β increased gradually during the last 6–7 days before oestrus and reached maximum values (124–373 pg/ml) at the time of the preovulatory LH peak. The first significant increase in plasma progesterone concentration occurred simultaneously with the LH peak. During oestrus (normally 3–5 days), progesterone levels rose steeply, attaining a mean concentration of 57·0 ± 17·5 ng/ml when the vixens went out of heat. Androstenedione and testosterone values changed similarly, both increasing at the beginning of pro-oestrus and reaching maximum values (805–1879 pg/ml and 328–501 pg/ml respectively) 1 day before to 1 day after the oestradiol-17β peak.