Advances in Fetal and Neonatal Physiology by Lubo Zhang & Charles A. Ducsay

Author:Lubo Zhang & Charles A. Ducsay
Language: eng
Format: epub
Publisher: Springer New York, New York, NY

Recently we also determined if the pregnancy specific changes observed in our in vitro model [7] were also seen in vivo [6] and thus have physiologic relevance in pregnancy. In this study, we utilized an in vivo ovine model restricting pregnancy to a single uterine horn [6, 137–139]. In Fig. 11.4 we show that Cx37 and 43 were both expressed and upregulated by the physiologic state of pregnancy in UAendo and/or uterine artery vascular smooth muscle (UAvsm) [6]. Moreover, UAvsm Cx37 and Cx43 were elevated by the follicular phase, but even more so by pregnancy; a physiologic state of high estrogen [15, 120, 125, 140, 141]. The nongravid unilateral side also showed elevations in UAvsm Cx37 and Cx43, demonstrating that systemic circulating hormones (e.g. estrogen) may partly regulate VSM connexins. This is consistent with another smooth muscle cell type in the myometrium, in which Cx43 is up-regulated when endogenous estrogen is elevated in labor [142]. Cx43 is classically categorized as a “contraction associated protein” elevated in labor when the estrogen/progesterone ratio is elevated [40, 142]. The pregnancy-associated fold changes of Cx37 were similar in UAendo and UAvsm suggesting that Cx37 synthesis may be co-regulated and we proposed this is the basis for the formation of myoendothelial GJs for heteromeric cell communication between UAendo and UAvsm [8, 9]. By contrast, pregnancy-induced Cx43 increases were much greater in UAendo than in UAvsm [8, 9] and specifically support a role for endothelial–endothelial homomeric cell communication.

Fig. 11.4Connexin 37 and Connexin 43 protein expression in ovine (a) uterine artery endothelium (UAendo) and (b) vascular smooth muscle (UAvsm) from luteal, follicular, nongravid/gravid unilateral pregnant, and control pregnant ewes. Uterine horns were ligated laterally before breeding, therefore restricting pregnancy to a single uterine horn yielding one horn that was gravid while the other was nongravid [6, 137–139]. Western Blot analysis comparing relative levels of connexin 37 and 43 in (a) UA endo and (b) UAvsm obtained from luteal (n = 8), follicular (n = 8), unilateral (nongravid vs. gravid; n = 15), and pregnant (n = 23) sheep. Data shown from these treatment groups are expressed as means ± SEM fold of Luteal. Different letters denote differences (P < 0.05). This figure is partly adapted from data originally reported [6]

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