Hormone Secretion in the Asian Elephant (Elephas maximus): Characterizationof Ovulatory and Anovulatory Luteinizing Hormone Surges

Abstract

In the elephant, two distinct LH surges occur 3 wk apart during the nonluteal phase of the estrous cycle, but only the second surge (ovLH) induces ovulation. The function of the first, anovulatory surge (anLH) is unknown, nor is it clear what regulates the timing of these two surges. To further study this observation in the Asian elephant, serum concentrations of LH, FSH, progesterone, inhibin, estradiol, and prolactin were quantified throughout the estrous cycle to establish temporal hormonal relationships. To examine long-term dynamics of hormone secretion, analyses were conducted in weekly blood samples collected from 3 Asian elephants for up to 3 yr. To determine whether differences existed in secretory patterns between the anLH and ovLH surges, daily blood samples were analyzed from 21 nonluteal-phase periods from 7 Asian elephants. During the nonluteal phase, serum LH was elevated for 1-2 days during anLH and ovLH surges with no differences in peak concentration between the two surges. The anLH surge occurred 19.9+/-1.2 days after the end of the luteal phase and was followed by the ovLH surge 20.8+/-0.5 days later. Serum FSH concentrations were highest at the beginning of the nonluteal phase and gradually declined to nadir concentrations within 4 days of the ovLH surge. FSH remained low until after the ovLH surge and then increased during the luteal phase. Serum inhibin concentrations were negatively correlated with FSH during the nonluteal phase (r = -0.53). Concentrations of estradiol and prolactin fluctuated throughout the estrous cycle with no discernible patterns evident. In sum, there were no clear differences in associated hormone secretory patterns between the anLH and ovLH surge. However, elevated FSH at the beginning of the nonluteal phase may be important for follicle recruitment, with the first anLH surge acting to complete the follicle selection process before ovulation.

Fecal 20-oxo-pregnane concentrations in free-ranging African elephants (Loxodonta africana) treated with porcine zona pellucida vaccine

“…For the remaining focal animals, 5-pregnan-3-ol-20-on concentrations were expressed as µg/g dried faeces and plotted against time (weeks) for each pZP-treated cow. Baseline values of 5-pregnan-3-ol-20-on concentrations were ascertained for each female using an iterative process as described by Brown et al [45,46]. The average was subsequently recalculated and the elimination process was repeated until there were no values greater than the mean plus 2 standard deviations (SD).…”

“…The remaining values yielded the baseline 5-pregnan-3-ol-20-on concentration. Ovarian cycle length and periodicity was then determined according to the procedure described by Brown et al [45,47]. Phase length estimates as well as ovarian cycle length estimates are given as mean ± SD.…”

Assessment of luteinizing hormone and prolactin immunoactivity in Asian and African elephant urine using assays validated for serum

“…Peak and baseline hormone concentrations were determined for each individual by an iterative process in which high values were excluded if they exceeded the mean plus 2 standard deviations (Brown et al, 1999). The highest concentration within a group of elevated samples was considered a peak.…”

“…In general, the elephant exhibits the longest estrous cycle of any mammal: 13-17 weeks in duration with a 4-6 week follicular phase and an 8-10 week luteal phase. Another unique aspect of the elephant estrous cycle is the occurrence of two LH surges about 20 days apart during the follicular phase (Kapustin et al, 1996;Brown et al, 1999). The anovulatory LH surge can be used to time artificial insemination and natural breeding attempts; however, the physiological function of this first surge is unknown.…”

The pattern of ovulation in the southern African spiny mouse (Acomys spinosissimus)

“…Individual baseline FPM values were evaluated using the method described in Brown et al (1999). The mean + 1.5 standard deviation (SD) from an individual's data set was calculated and all concentrations that exceeded this value were excluded.…”