(M169) PULSATILITY OF LUTEINIZING HORMONE (LH) RELEASE DURING THE ANOVULATORY AND OVULATORY LH PEAKS IN THE AFRICAN ELEPHANT, Loxodonta africana.
Dahl, Nancy1, Blasko, David2, Roser, Janet1, 1 University of California, Davis, CA2 Six Flags Marine World, Vallejo, CA
ABSTRACT- Elephants have two LH peaks per follicular phase, separated by approximately 20 days, where ovulation occurs only after the second peak, the ovulatory (Ov) LH peak. Progesterone levels also only increase with the OvLH peak, remaining at baseline for the anovulatory (An) LH peak. Previous studies in our lab demonstrated an early rise in progesterone the day before and the day of the OvLH peak, suggesting that progesterone may play a role in driving ovulation in the elephant. Due to the concentrations of the two LH peaks being statistically equal when using daily blood sampling, intensive sampling was used to look at the pulse frequency and amplitude of LH during the two peaks. Previous studies in other species have demonstrated that progesterone feedback affects LH pulse frequency and amplitude, and that the pulsatility of LH changes as the time of ovulation approaches. Blood was drawn at five-minute intervals for a period of three hours and five minutes in one African female during the two peaks. A validated RIA was used, with purified elephant LH as standard, iodinated equine LH as tracer, and an anti-bovine LH monoclonal antibody (518B7) as the primary antibody. The frequency of the AnLH peak was 2.92 pulses/hour with an average duration of 26.1 minutes and a range of 20-50 minutes. The average amplitude was 1.65 ng/ml with a range of 0.55-3.25 ng/ml. The frequency of the OvLH peak was 1.33 pulses/hour, with an average duration of 52.5 minutes and a range of 45-60 minutes. The average amplitude was 1.29 ng/ml with a range of 1.16-1.56 ng/ml. These preliminary data suggest that an early rise in progesterone may affect a change in the pulsatile LH release that is necessary to drive ovulation.
KEY WORDS: Loxodonta africana, ovulation, LH pulsatility, progesterone