It is well established that uterine oxytocin receptors (OTRs) are strongly up-regulated immediately before parturition as well as in response to estrogen (E2) administration. Progesterone (P4), on the other hand, induces a rapid down-regulation. We recently cloned the rat OTR gene and characterized its expression in the rat uterus. In this study, we examined the regulation of OTR messenger RNA (mRNA) levels in rat uterus during pregnancy, the estrous cycle, and in response to gonadal steroid treatment. OTR mRNA levels increased more than 25-fold during gestation: 4.5-fold during the first 21 days and 6-fold within 24 h between day 21 and the onset of parturition. Uterine OTR mRNA levels fell rapidly by 85% within 24 h following parturition. By in situ hybridization, OTR mRNA was localized specifically to the longitudinal and circular layers of the myometrium but was not detected in the endometrium. During the estrous cycle, OTR mRNA levels increased 2-fold between metestrus and proestrus, whereas oxytocin (OT) binding rose more than 10-fold within this same interval. Treatment of ovariectomized rats with E2 lead to a significant increase in both OTR mRNA levels (4.4-fold) and OT binding (< 6-fold). Cotreatment with P4 strongly reduced OT binding by 75% (P < 0.01) but did not significantly affect the E2-induced rise in OTR mRNA (11% decrease, P > 0.1). Our data suggest that the increased expression of OT binding sites observed at the onset of labor and at proestrus is mediated, at least in part, by an E2-induced up-regulation of OTR gene expression. However, it also appears that OTR mRNA levels are not the sole determinants of uterine OT binding. Specifically, P4-mediated OTR down-regulation cannot be explained by an effect on OTR mRNA accumulation and may involve novel mechanisms acting at translational or posttranslational levels.
In elderly, high-risk surgical patients, sutureless aortic valve replacement (AVR) can often be an alternative to conventional AVR; shorter aortic cross-clamp and cardiopulmonary bypass times are the chief advantages. We compared the outcomes of sutureless AVR with those of conventional AVR in 70 elderly patients who underwent concomitant cardiac surgical procedures. We retrospectively analyzed the cases of 42 men and 28 women (mean age, 70.4 ± 10.3 yr; range, 34-93 yr) who underwent cardiac operations plus AVR with either a sutureless valve (group 1, n=38) or a conventional bioprosthetic or mechanical valve (group 2, n=32). Baseline patient characteristics were similar except for worse New York Heart Association functional status and the prevalence of diabetes mellitus in group 1. In group 1, the operative, cross-clamp, and cardiopulmonary bypass times were shorter (all =0.001), postoperative drainage amounts were lower (=0.009), hospital stays were shorter (=0.004), and less red blood cell transfusion was needed (=0.037). Echocardiograms before patients' discharge from the hospital showed lower peak and mean aortic gradients in group 1 (mean transvalvular gradient, 8.4 ± 2.8 vs 12.2 ± 5.2 mmHg; =0.012). We found that elderly, high-risk patients who underwent multiple cardiac surgical procedures and sutureless AVR had better hemodynamic outcomes and shorter ischemic times than did patients who underwent conventional AVR.
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