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Many molecules, including steroid and peptide hormones, prostaglandins and cytokines, regulate the preparation, initiation and progression of parturition in mammals. Gene targeting studies show that, in the knockout mice of steroid 5α-reductase type 1 gene, prostaglandin F 2α receptor gene and cytosolic phospholipase A 2 gene, parturition was severely disturbed, although live offspring were delivered by Caesarean section. Relaxin gene-disrupted mice also showed protracted labour. However, most knockout mice in which the steroid hormone, prostaglandin, cytokine or peptide hormone (for example, oxytocin, corticotrophin releasing hormone and endothelin) endocrine-paracrine systems are disrupted are inadequate for analysis of the mechanism of parturition because they die before reaching reproductive age or are infertile, or because they reproduce normally. A conditional knockout strategy, for example, using the Cre-LoxP system, should be considered for investigating the biochemical background of parturition to overcome these problems.hormones produced by the fetus can cross the placenta to some extent and may affect maternal (GR +/-) uterine function, although the maternal GR is partially ablated. However, it would appear that disturbed fetal corticosterone metabolism does not affect parturition in mice.Near to term of human pregnancy, there is a 100-fold higher concentration of circulating oestrogens, produced mainly from placental tissue, than in non-pregnant women in whom the oestrogens derive predominantly from the ovary. As the oestrogen concentrations increase gradually towards the onset of parturition, maternal oestrogen is important for uterine preparedness. Oestrogen receptor knockout mice (ERα -/-) are externally normal in both sexes. Internally, only ERα -/-females showed noticeable gross differences from normal females. ERα -/-females are completely infertile, with hypoplastic uteri and hyperemic ovaries (Lubahn et al., 1993), so that any effect on parturition cannot be studied. Details of oestrogen receptor β(ERβ)-knockout mice have not yet been published. Oestrogens are the final products of the steroidogenesis pathway. Therefore, the disruption of aromatase cytochrome P450, that is, the cyp19 gene product, could impair the biosynthesis of oestrogens without disturbing the biosynthesis of other steroid hormones. Aromatase knockout mice have been reported; again aromatase -/-(ArKO) homozygous females were completely infertile (Fisher et al., 1998). Adult male and female ArKO mice exhibit higher concentrations of testosterone and androstenedione, the precursors of oestrogens; however, the authors did not investigate fetal or neonatal androgen concentrations. It is not known whether an oestrogen supplement given to ArKO mice from the neonatal period might recover female fertility. If it is possible for female ArKO mice to become pregnant, the role of oestrogen during pregnancy could be analysed by studying the effects of stopping oestrogen supplementation at different stages of pregnancy. Natural aromatas...

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To elucidate the mechanism by which myometrial vasopressin injection promotes hemostasis during myomectomy, we examined the expression of vasopressin V1a receptor transcripts in the myometrium. Vasopressin V1a receptor expression was ubiquitous, and the transcripts were detected in the myometrium not only of cycling and pregnant patients, but also of postmenopausal or GnRH agonist-treated patients. Based on these observations, we applied intraoperative myometrial vasopressin injection during myomectomy in a non-randomized study in a total of 84 patients. Vasopressin injection significantly reduced the intraoperative blood loss and postoperative hemoglobin fall in patients without and with GnRH agonist pretreatment. No serious complications occurred on account of the vasopressin injection. We conclude that intraoperative vasopressin injection is effective as a hormonal tourniquet even in GnRH agonist-pretreated myomectomy.

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