Ovine interferon-tau (oIFN-tau) may stabilize endometrial progesterone receptor (PR) and/or inhibit estrogen receptor (ER) gene expression during pregnancy recognition to suppress endometrial oxytocin receptor (OTR) formation and production of luteolytic prostaglandin (PG) F2 alpha pulses. This study determined whether or not oIFN-tau stabilized PR expression in the endometrium during PR down-regulation by continuous exposure to progesterone. Twenty cyclic ewes were bilaterally ovariectomized and fitted with uterine catheters on Day 2 of the estrous cycle (Day 0 = estrus). Ewes were then assigned randomly to be treated, in a 2 x 2 factorial arrangement, with recombinant oIFN-tau (roIFN-tau; 2 x 10(7) antiviral units per ewe per day) or control proteins (6 mg/day) by intrauterine injection from Days 10 to 14, and with daily i.m. injections of 20 mg progesterone from Days 2 to 14 (P) or progesterone from Days 2 to 14 plus 50 micrograms estradiol-17 beta from Days 12 to 14 (P+E). All ewes were hysterectomized on Day 15. Endometrial PR mRNA (p < 0.01) and protein (p < 0.03) were higher in ewes receiving P+E than in those receiving P alone. However, the increase in PR mRNA and protein was not as great in the endometrium of roIFN-tau-treated ewes as compared to controls (p < 0.08, treatment x steroid). In ewes receiving P alone, PR mRNA and immunoreactive PR were localized to stroma and deep glandular epithelium and were not present in endometrial luminal and shallow glandular epithelium. Values for endometrial ER mRNA (p < 0.02) and ER protein (p < 0.01) were greater in controls than in roIFN-tau-treated ewes regardless of steroid treatment. Among controls, ER mRNA and immunoreactive ER protein were present in the luminal and glandular epithelium and were increased in the epithelium and stroma in ewes receiving estrogen. In contrast, endometrial ER mRNA and immunoreactive ER protein were very low or absent in the endometrium of roIFN-tau-treated ewes and were not increased by estrogen. Among controls, endometrial OTR density was greater (p < 0.09) in ewes treated with P+E than in those treated with P alone. In roIFN-tau-treated ewes, endometrial OTR density was lower (p < 0.01) than in the controls. Results indicate that roIFN-tau did not stabilize or prevent autologous down-regulation of PR mRNA or protein expression in the endometrium. However, roIFN-tau did suppress endometrial ER expression and OTR formation in ewes regardless of steroid treatment. The results support the hypothesis that the antiluteolytic effects of oIFN-tau are to suppress endometrial ER gene expression in the endometrial epithelium, thereby inhibiting formation of OTR and production of luteolytic PGF2 alpha pulses.

We analyzed the pattern of gap junction protein (connexin) expression in vivo by indirect immunofluorescence. In normal rat lung sections, connexin (Cx)32 was expressed by type II cells, whereas Cx43 was more ubiquitously expressed and Cx46 was expressed by occasional alveolar epithelial cells. In response to bleomycin-induced lung injury, Cx46 was upregulated by alveolar epithelial cells, whereas Cx32 and Cx43 expression were largely unchanged. Given that Cx46 may form gap junction channels with either Cx43 or Cx32, we examined the ability of primary alveolar epithelial cells cultured for 6 days, which express Cx43 and Cx46, to form heterocellular gap junctions with cells expressing other connexins. Day 6 alveolar epithelial cells formed functional gap junctions with other day 6 cells or with HeLa cells transfected with Cx43 (HeLa/Cx43), but they did not communicate with HeLa/Cx32 cells. Furthermore, day 6 alveolar epithelial cells formed functional gap junction channels with freshly isolated type II cells. Taken together, these data are consistent with the notion that type I and type II alveolar epithelial cells communicate through gap junctions compatible with Cx43.

This study determined whether intrauterine injection of interferon-tau (IFN tau) could block luteolysis in cyclic ewes treated with a luteolytic dose of 17 beta-estradiol benzoate (E) on day 12 of the estrous cycle. Thirty-two ewes were fitted with uterine catheters on day 5 of the estrous cycle and treated with recombinant ovine IFN tau (2 x 10(7) antiviral units/ewe/day) or control proteins (6 mg/day) by intrauterine injection from day 10 until hysterectomy. At 1900 h on day 12, all ewes received 750 micrograms E, im, and were hysterectomized 12, 24, 36, or 48 h post-E administration. Plasma concentrations of progesterone declined in control animals but increased in IFN tau-treated ewes after E injection (P < 0.01, treatment x day interaction). Likewise, total corpus luteum weight decreased in control but not IFN tau-treated ewes after E administration (P < 0.02, treatment x time interaction). In control ewes, endometrial estrogen receptor (ER) messenger RNA (mRNA; P < 0.03) and progesterone receptor (PR) mRNA (P < 0.10) increased after 12 h, whereas concentrations of ER protein (P < 0.02) and PR protein (P < 0.04) increased after 24 h. In situ hybridization and immunohistochemical analyses indicated that ER gene expression increased first in the epithelium at 12 h and then in the stroma by 48 h, whereas PR gene expression first increased in the stroma and then in the epithelium. In control ewes, endometrial oxytocin receptor (OTR) density increased (P < 0.10) after 12 h, with the largest increase occurring between 36-48 h. In IFN tau-treated ewes, endometrial ER mRNA and protein and OTR density did not increase after E administration. Levels of PR mRNA increased (P < 0.01) between 12-36 h, but decreased after 36 h. PR mRNA abundance increased between 12-36 h in the stroma, but not in the epithelium. Concentrations of PR protein were low and did not change in IFN tau-treated ewes. Immunoreactive PR protein was present at low levels in the stroma of all IFN tau-treated ewes. The results indicate that induction of luteolysis by E in control ewes involved sequential increases in endometrial ER mRNA and ER protein in the epithelium that preceded maximal increases in OTR density. Intrauterine injection of recombinant ovine IFN tau prevented luteolysis by inhibiting estrogen-induced increases in endometrial ER and OTR gene expression.

This study examines the distribution and abundance of progesterone receptors (PR) and estrogen receptors (ER) in the decidua basalis (DB) during proliferation (Days 8-12 of gestation) and regression (Days 14-21) in the rat. Stromal cells of the DB and metrial gland exhibited strong nuclear immunostaining for PR throughout gestation. Nuclear localization of ER was detectable only between Days 8-12. The heavily granulated natural killer cells were always negative for PR and ER. DB were dissected between Days 8 and 17 to measure progesterone (P4)-binding sites and receptor proteins by Western blotting. The latter revealed four specific PR isoforms: B (110 kDa), A1 (90 kDa), A2 (76-82 kDa), and C (60-64 kDa). Stromal cell nuclei contained more than 50% of P4-binding sites during DB proliferation but less than 22% during regression (p < 0.05). PR-A and PR-B expression was greatest at proliferative stages (p < 0.05). PR-C increased in relative abundance during DB regression. Two ER isoforms of 66 kDa and 49 kDa were revealed. The 66-kDa ER, the most abundant form, was maximally expressed during proliferation, declining 71% by Day 12 (p < 0.01), whereas the 49-kDa form accounted for up to 90% of ER during regression. Northern blot analysis revealed three prominent transcripts of approximately 11, 7, and 4 kilobases (kb) for PR mRNA, which declined markedly at Days 14 to 17 (p < 0.05), and one of 6.0 kb for ER mRNA, which declined markedly on Day 17 (p < 0.05). Our study establishes that the DB expresses heterogeneity of receptor message and proteins. We propose that preferential expression of receptor isoforms in late pregnancy limits P4 action and promotes DB regression in spite of invariant levels of serum P4, P4-binding sites, and total receptor protein.

This study examines the distribution of the estrogen receptor (ER) in the mesometrial decidua basalis (DB) and the chorioallantoic placenta between Days 8 and 21 of pregnancy (Day 1 = presence of vaginal sperm) and its regulation by estradiol and progesterone. Immunocytochemistry revealed that ER was localized within nuclei of cells of the DB but not in trophoblastic cells (Day 10) or in cells of the junctional zone (JZ) or labyrinth zone (LZ). Western blot analysis and estradiol binding assays of DB, JZ, and LZ also revealed that only DB expressed ER. Native ER (66 kDa) was most abundant on Days 8 and 9, and declined 67% on Day 11 (p < 0.01), becoming barely detectable by Day 17. A truncated ER moiety (49 kDa) gradually increased, becoming the dominant form on Day 13. The effects of estradiol and progesterone on ER were studied during periods of growth and decline of DB (i.e., Days 8-10 and 12-14, respectively). Rats were ovariectomized on Day 8 or 12 and treated with estradiol daily (0.2, 0.75, or 2 micrograms, s.c.), with a progesterone pellet, or with both, for 48 h. Progesterone, but not estradiol, stimulated the 66-kDa ER moiety and ER binding activity (p < 0.01). Estradiol administered with progesterone antagonized progesterone action, at least in part, by enhancing expression of the 49-kDa ER at the expense of the native form (p < 0.01). Thus, progesterone up-regulated ER whereas estradiol down-regulated ER in rat DB.