A correlative study of porcine endometrium and hormone levels during early lactation and the late luteal phase.

This study sought to determine what morphological similarities there were between sow uterus 6-10 days post-partum and during the late luteal phase of the estrous cycle (day 14 post-estrum). An attempt to assess blastocyst receptivity was made. SEM examination of the uterine surfaces in all sows revealed two distinct types of gland openings: 1) Several wider openings (40-60 microM diam.) were always surrounded by large numbers of ciliated cells. At day 7 post-partum distinct epithelial "ridges" surrounding these ciliated patches were very pronounced and consisted of proliferating/differentiating non-ciliated cells. These "ridges" seemed to appear as "valleys" on day 8 post-partum and were densely populated with cells bearing a single cilium. 2) Smaller, (2-4 micron diam.) more numerous gland openings were not associated with large numbers of ciliated cells. The larger gland openings were more numerous in post-partum uterus. Surface and glandular epithelial heights were similar in all sows. Circulating levels of steroids and prostaglandins were very low in post-parturient sows and appeared to exert little effect on cell morphology. Secretory cells lacking microvilli appeared around days 6 and 7 post-partum but were less prominent around days 8-10 post-partum. Several similarities were noted between the luteal phase uterus and the uterus at days 8 and 9 post-partum. These included cell heights, lipid inclusions and large secondary lysosomes, the amount of breakdown within the surface epithelium, and the densities of the zona compacta and the zona spongiosa. It was concluded that attempts at blastocyst implantation might be feasible at around days 8 and 9 post-partum.