In all mammalian species, progesterone is essential to both the preparation for, and maintenance of, pregnancy. The 20α-hydroxysteroid dehydrogenase (20α-HSD) enzyme predominantly converts progesterone into its biologically inactive form 20α-hydroxyprogesterone, thereby regulating its activity. Thus, to directly assess sexual maturation in the MediKinetics micropig®, we analyzed the concentration of the steroid hormones progesterone and estradiol during the estrous cycle.Our results show that the progesterone level exhibited by the analyzed micorpig® was low at the beginning of the estrous cycle, and then abruptly increased to 30.32±10.0 ng/mL and 46.37±11.0 ng/mL by days 9 and 11 of the cycle, respectively. It reached the highest level 55.87±3.5 ng/mL on day 13 of the estrous cycle, before decreasing to 46.58±13.1 ng/mL and 10.0±7.6 ng/mL by days 15 and 17 of the cycle, respectively. In contrast, the estradiol level was shown to be highest (27.13±11.2 ng/mL) at the initiation of the estrous cycle, after which point it decreased to 13.29±6.5 ng/mL and 10.94±5.9 ng/mL by days 4 and 5 of the estrous cycle, respectively. By day 17 of the estrous cycle, the estradiol level decreased to 4.13±7.6 ng/mL.We anticipate that these results will provide useful information to enable the study of human ovulation and reproductive physiology using the MediKinetics micoripig® as a model system. We recommend further investigation to elucidate the functional mechanisms underlying the regulation of sexual maturation in the MediKinetics micropig®.

Equine chorionic gonadotropin (eCG) is a unique molecule that elicits the response characteristics of both follicle- stimulating hormone (FSH) and luteinizing hormone (LH) in other species. Previous studies from this laboratory had demonstrated that recombinant eCG (rec-eCG) from Chinese hamster ovary (CHO-K1) cells exhibited both FSH- and LH-like activity in rat granulosa and Leydig cells. In this study, we analyzed receptor internalization through rec-eCGs, wild type eCG (eCGβ/α) and mutant eCG (eCGβ/αΔ56) with an N-linked oligosaccharide at Asn56 of the α-subunit. Both the rec-eCGs were obtained from CHO-K1 cells. The agonist activation of receptors was analyzed by measuring stimulation time and concentrations of rec-eCGs. Internalization values in the stably selected rat follicle-stimulating hormone receptor (rFSHR) and rat luteinizing/ chorionic gonadotropin receptor (rLH/CGR) were highest at 50 min after stimulation with 10 ng of rec-eCGβ/α. The dose-dependent response was highest when 10 ng of rec-eCGβ/α was used. The deglycosylated eCGβ/αΔ56 mutant did not enhance the agonist-stimulated internalization. We concluded that the state of activation of rFSHR and rLH/CGR could be modulated through agonist-stimulated internalization. Our results suggested that the eLH/CGRs are mostly internalized within 60 min by agonist-stimulation by rec-eCG. We also suggested that the lack of responsiveness of the deglycosylated eCGβ/ αΔ56 was likely because the site of glycosylation played a pivotal role in agonist-stimulated internalization in cells expressing rFSHR and rLH/CGR.