Expressions and regulation of endothelial and inducible nitric oxide synthases in mouse uterus during the estrous cycle and early pregnancy

Abstract

Nitric oxide (NO) has been implicated in many cellular processes. We examined the temporal and spatial expressions of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) in mouse uteri during the estrous cycle and early pregnancy, as well as the regulation of eNOS and iNOS by estradiol (E2) and progesterone (P4) in ovariectomized mouse uteri using in situ hybridization and immunohistochemistry. Our results showed that positive eNOS and iNOS signals were localized in the uterine luminal epithelium and glandular epithelium during the estrous cycle. In ovariectomized mice, both E2 and P4 regulated the expression of eNOS and iNOS. During early pregnancy, eNOS and iNOS were detected not only in epithelium, but also in the primary decidual zone surrounding implanting embryos on day 6 of pregnancy, and in the whole decidualized stroma on day 7 of pregnancy. In conclusion, the results demonstrated that two NOS isoforms were localized in mouse uteri in specific temporal and spatial patterns during the estrous cycle and early pregnancy, and ovarian hormones can regulate their expression. Furthermore, the data suggest that the expression of NOS during the peri-implantation period might lead to enhance NO production, which could promote embryo implantation.

Select Nutrients in the Ovine Uterine Lumen. V. Nitric Oxide Synthase, GTP Cyclohydrolase, and Ornithine Decarboxylase in Ovine Uteri and Peri-Implantation Conceptuses1

“…In that study, NOS3 protein was detected in endothelial cells, as well as uterine LE and GE in intercaruncular areas of uterine endometrium [25], whereas NOS2 was most abundant in stromal cells, mainly macrophage/ monocyte lineage cells, in intercaruncular areas, and its abundance did not change during late pregnancy [25,43]. This expression pattern for NOS3 in uterine endometrium of late pregnant ewes [25] is consistent with that for mice [17], rats [18], mares [19], and humans [20]. Patterns of expression for NOS2 appear to be inconsistent among these different species [17].…”

“…This expression pattern for NOS3 in uterine endometrium of late pregnant ewes [25] is consistent with that for mice [17], rats [18], mares [19], and humans [20]. Patterns of expression for NOS2 appear to be inconsistent among these different species [17]. Because expression of NOS2 in uterine endometia of cyclic and early pregnant ewes is low to undetectable and not affected by pregnancy status, P4, or IFNT, there is little evidence to suggest that NOS2 plays a significant role in NO synthesis in ovine uteri during early pregnancy.…”

“…Among the three isoforms of the NOS, NOS1 was the most abundant in ovine endometria (Fig. 1), but NOS2 has been reported to be the most highly expressed in rat uteri [18], whereas NOS2 and NOS3 are more abundant in the uteri of mice [17]. Also of interest is the observation that the stimulatory phosphorylated form of NOS3 decreased in uterine epithelia after Day 12 of the estrous cycle and pregnancy, which corresponds to the time of loss of expression of progesterone receptors in those cells [35].…”

“…Among these species of mammals, the various isoforms of NOS exhibit differential temporal and spatial expression in uterine endometrium [17][18][19][20][22][23][24][25] and respond differentially to regulation of expression by progesterone (P4) and/or estrogen [17,22,[26][27][28][29][30]. In sheep, activities of NOS3 and NOS2 increase in the placenta and uterine endometria during early and mid gestation [31], whereas ODC1 activity peaks in midpregnancy in the placenta and uterine endometrium [32].…”

“…To date, different isoforms of NOS have been identified in the endometria of mice [17], rats [18], and mares [19] during the estrous cycle, and in humans [20,21] during the menstrual cycle, pregnancy, or premenopausal and postmenopausal stages. Among these species of mammals, the various isoforms of NOS exhibit differential temporal and spatial expression in uterine endometrium [17][18][19][20][22][23][24][25] and respond differentially to regulation of expression by progesterone (P4) and/or estrogen [17,22,[26][27][28][29][30].…”