Profiles of reproductive hormone in the microminipig during the normal estrous cycle.

We investigated changes in the peripheral plasma concentrations of ovarian steroids and gonadotropins throughout the estrous cycle of the Microminipig (MMpig), a novel experimental animal model. The mean (± standard error of the mean (SEM)) duration of estrous and the estrous cycle in seven animals was 66.0 ± 5.2 h and 20.6 ± 0.3 days, respectively. A luteinizing hormone (LH) surge was observed 16.5 ± 6.5 h after the onset of estrous in six out of the seven animals. The LH peak and the duration of the LH surge were 14.0 ± 4.5 ng/ml and 34.0 ± 2.0 h, respectively. Plasma progesterone concentrations started to decline on Day 7 (Day 0 = the day of the LH peak) and increased from Day 4. Estradiol-17β levels increased from Day 3 and reached a maximum (37.0 ± 1.6 pg/ml) on Day 0.75. Follicle-stimulating hormone (FSH) concentrations showed a first and second surge on Days 0 and 1.75. An inverse relationship between FSH and estradiol-17β concentrations was noted before the LH surge. The characteristics of estrous and the gonadotropin and ovarian steroid profiles throughout the estrous cycle of MMpigs are similar to those of domestic pigs and other miniature pig strains.