Endocrine Correlates of Reproduction in the Wolf. I. Serum Progesterone, Estradiol and LH during the Estrous Cycle 1

Supported in part by the U. S. Fish and Wildlife Service, the Bush Foundation and Varian Associates.

Biology of Reproduction, Volume 21, Issue 5, 1 December 1979, Pages 1057–1066, https://doi.org/10.1095/biolreprod21.5.1057

Cite

U. S. Seal and others , Endocrine Correlates of Reproduction in the Wolf. I. Serum Progesterone, Estradiol and LH during the Estrous Cycle, Biology of Reproduction, Volume 21, Issue 5, 1 December 1979, Pages 1057–1066, https://doi.org/10.1095/biolreprod21.5.1057

Abstract

The estrous cycle of 10 intact female wolves, aged 8 months-8 years at the initiation of the study, was characterized in terms of vaginal smears, behavioral observations and serum concentrations of estradiol-17β, progesterone and luteinizing hormone (LH) from January through June. No estrous cycles occurred in these animals between June and December. All were housed with male wolves. Two pups and 1 adult remained anestrous during this interval. One pup and 2 adults produced litters between May 4–6. Four adults exhibited endocrine changes similar to those of the pregnant animals but no litters or signs of abortion were observed. The duration of proestrus was 15.7 ± 1.6 days (X̄ ± SEM, n = 6), of estrus 9.0 ± 1.2 days (n = 4) and of the luteal phase 63 ± 2 days (n = 6). The duration of pregnancy was between 60–65 days. The anestrous females (86 blood samples) had 6 progesterone values between 1–2 ng/ml and the remainder below 1 ng/ml. Their estradiol-17β concentrations varied between 5–20 pg/ml. Values for LH varied between 0.1–2 ng/ml, except for 1 value above 15 ng/ml for each of the 2 anestrous pups on 12 January.

The 7 estrous animals (260 samples) included 1 pup and 2 adults that delivered litters. Estradiol-17β varied between 10–20 pg/ml during proestrus, peaked at 30–70 pg/ml late in proestrus and fluctuated between 10–30 pg/ml during pregnancy or the duration of luteal activity in the nonpregnant animals. The preovulatory LH rise, 5–15 ng/ml, extended over 3 days during and immediately following the peak estradiol-17β values. An earlier elevation in LH was observed in 3 of the estrous animals. Progesterone began increasing during the LH surge and peaked 11–14 days later at 22–40 ng/ml. Progesterone concentrations greater than 3 ng/ml were maintained for 56–68 days in 6 of the 7 animals exhibiting estrus. Progesterone concentrations declined at parturition but continued to fluctuate between 0.2–3 ng/ml for 3–6 weeks.

Author notes

Supported in part by the U. S. Fish and Wildlife Service, the Bush Foundation and Varian Associates.