Uterine glands of the pig during pregnancy

Abstract

The ultrastructure of the porcine uterine glands is described from material taken from 11 pregnant pigs at exactly known stages of gestation (day 30; 58; 80; 100; 110). Fixation was performed by perfusion via a branch of the uterine artery and the tissue was routinely processed for electron microscopy. Additionally, cytochemical studies (phosphotungstic acid reaction for glycoproteins, according to Rambourg 1967; acid phosphatase reaction; ultrastructural localization of cellular iron, according to Parmley et al. 1978) were performed. On day 30 of pregnancy the uterine glands are coiled, simple tubular glands with a narrow lumen. The epithelial lining is simple columnar and consists basically of two cell types, ciliated cells and secretory cells. The secretory activity of the glandular epithelium is low; only a few secretory granules are present in the supranuclear cytoplasm. At midpregnancy the ultrastructure of the glands has significantly changed and the cells now show all the characteristics of high secretory activity: numerous parallel cisternae of rough endoplasmic reticulum, an extensively developed Golgi apparatus and many secretory granules which give a positive reaction for acid phosphatase and glycoproteins. The lumina of the glands are significantly enlarged and filled with a great amount of a granular, acid phosphatase-positive material. In the last third of pregnancy, only minor changes in the ultrastructure of the uterine glands are observed. The secretory activity is still high. The amount of rough endoplasmic reticulum has further increased and parallel arrays of cisternae occupy a considerable part of the supranuclear cytoplasm. The importance of the uterine secretion for embryonic nutrition and development is only partly understood. One of the secreted glycoproteins, uteroferrin, is believed to play an important role in the iron transfer from mother to fetus. From midpregnancy onward, a special cell type, the "granule laden cell" is found scattered between normal secretory cells of the uterine glands. Contrary to the opinion of Perry and Cromby (1982), we could demonstrate that these cells frequently extend to the lumen of the gland; hence the term "basal cell" seems inappropriate for this cell type.

Effects of long-term progesterone on developmental and functional aspects of porcine uterine epithelia and vasculature: progesterone alone does not support development of uterine glands comparable to that of pregnancy

“…There are few descriptions of the hypertrophy and hyperplasia that the uterine GE of pigs undergo as GE increases production of histotroph, particularly between days 30 and 90 of pregnancy (Knight et al 1977, Basha et al 1980, Perry & Crombie 1982, Sinowatz & Friess 1983. Endometrial GE development, or adenogenesis, begins during early postnatal life in pigs (Bartol et al 1993, Gray et al 2001.…”

“…The GE remain simple, coiled, and tubular through day 30 of pregnancy, but develop characteristics of increased secretory activity by day 35 when GE cells exhibit extensive rough endoplasmic reticulum with flocculent-filled cysternae. By midpregnancy, the lumens of uterine glands are greatly enlarged and filled with secretory products (Perry & Crombie 1982, Sinowatz & Friess 1983. In the present study, there were no differences in the number of uterine glands per unit area of shallow endometrium (near the LE) between ovariectomized gilts treated with either CO or progesterone for 40 days, but adenogensis was clearly unable to keep pace with growth of the uterine wall as GE were decreased in deep endometrium (near the myometrium) of progesterone-treated pigs compared with CO-treated pigs.…”

“…However, the histomorphology of uterine GE and structural modifications to endometrium, including vasculature, for increased secretory activity have never been examined in ovariectomized gilts given exogenous progesterone through the critical window of days 30-40 when ultrastructural adaptations of uterine epithelia for secretion have been noted in pigs (Perry & Crombie 1982, Sinowatz & Friess 1983. Therefore, in order to address the role progesterone serves to modulate molecular factors within the endometrium, impacting placental function and pregnancy maintenance in the absence of confounding factors due to the presence of the ovary and conceptuses, gilts were ovariectomized on day 12 of the estrous cycle and treated daily with progesterone for 28 days to assess the effects of long-term progesterone on the morphology and expression of selected structural proteins by porcine uterine LE and GE in the absence of conceptus and/or ovarian factors.…”

Effects of long-term progesterone exposure on porcine uterine gene expression: progesterone alone does not induce secreted phosphoprotein 1 (osteopontin) in glandular epithelium

“…The GE remain simple, coiled, and tubular until day 30 of pregnancy, but shows numerous characteristics of high secretory activity by day 35. By mid-pregnancy, the lumens of uterine glands are greatly enlarged and filled with secretory products (Perry & Crombie 1982, Sinowatz & Friess 1983. During early pregnancy, the pig uterus secretes only moderate levels of histotroph, but total uterine secretions increase dramatically after day 30 of pregnancy (Knight et al 1974, Schlosnagle et al 1974, Basha et al 1980.…”

“…The second involves 10-15% of the remaining conceptuses and occurs during early to midgestation (Pope 1994). This second period of conceptus loss correlates with increasing GE development, endometrial secretory activity, placental growth and differentiation, and fetal growth (Knight et al 1974, 1977, Perry & Crombie 1982, Sinowatz & Friess 1983, Dwyer et al 1994. Much is not understood about the mechanisms that underlie these waves of conceptus loss.…”