Localization of orexin A and orexin B in the porcine uterus.

The presence of orexins and their receptors in gonads indicate that these hormones participate in the control of reproductive functions. The aim of the study was to compare the expression of the prepro-orexin (PPO) gene in porcine endometrium and myometrium and the intensity of OXA- and OXB-immunoreactivity in the following uterine structures: endometrial glandular and luminal epithelium and stroma as well as the myometrial longitudinal and circular muscles during the four stages (days 2-3, 10-12, 14-16, 17-19) of the estrous cycle. The highest expression of PPO mRNA was observed in the endometrium and the myometrium on days 14-16 of the cycle. The expression of the PPO gene on days 2-3 was more pronounced in the myometrium than in the endometrium, whereas on days 17-19 the gene expression was markedly higher in the endometrium. The OXA signal intensity was highest on days 2-3 in the luminal epithelium and on days 2-3 and 10-12 in the stroma. In circular muscles of the myometrium, the highest immunoreactivity was found on days 2-3 and 10-12, while in longitudinal muscles on days 2-3. OXB-immunoreactivity was highest on days 10-12 in longitudinal muscles, on days 17-19 in glandular epithelium and stroma, and on days 10-12 and 14-16 in luminal epithelium. Our results suggest that orexin A and B are produced in the porcine uterus and that their release is dependent on the hormonal status of animals.