Serum concentrations of E and LH over the estrous cycle
| Diestrus | Proestrus | Estrus | ||
|---|---|---|---|---|
| AM | PM | |||
| Estradiol (pg/ml) | 16 ± 4a | 55 ± 9b | 57 ± 9b | 23 ± 8a |
| LH (ng/ml) | 0.9 ± 0.3a | 0.9 ± 0.2a | 16.2 ± 1.1b | 0.8 ± 0.1a |
Data are presented as the mean ± SEM. Serum levels of E were elevated during the morning [2 hr after lights on (AM)] and evening [1 hr before lights off (PM)] of proestrus compared with diestrus II and estrus (all p < 0.05). Levels of serum LH were elevated only during the evening of proestrus (p < 0.0001 compared with all other groups).