The influence of oestrogen and progesterone on the actions of two calcium entry blockers in the rat uterus

Author:

Downing S. J.,Hollingsworth M.,Miller M.

Abstract

ABSTRACT The potency and maximum effect of the calcium entry blocker nifedipine as an inhibitor of uterine contractions in vivo are increased in rats in late pregnant compared with non-pregnant rats. The influence of ovarian steroids produced during pregnancy (oestrogen and progesterone) on the potency and maximum effect of two calcium entry blockers (nifedipine and diltiazem) against uterine contractions during i.v. infusion was therefore investigated in anaesthetized non-pregnant rats. The influence of pregnancy on the relationship between serum concentrations of diltiazem during i.v. infusion and uterine and cardiovascular effects was also investigated. A twofold increase in the potency of nifedipine as an inhibitor of uterine contractions was observed in rats treated with oestrogen or oestrogen plus progesterone compared with rats treated with corn oil. There was no change in potency in rats receiving progesterone alone. Maximum inhibition of uterine contractions by nifedipine was significantly increased by all three hormone treatments. A twofold increase in the potency of diltiazem and a significant increase in maximum inhibition of uterine contractions was observed in rats in late pregnancy compared with non-pregnant rats. No increase in potency of diltiazem in reducing blood pressure or heart rate was observed in rats in late pregnancy. No significant difference in potency of diltiazem against uterine contractions was observed in rats treated with oestrogen, progesterone or oestrogen plus progesterone. In order to determine if the hormone-induced changes in the potency of nifedipine against contractions in vivo were due to a direct effect of the ovarian steroids on voltage-operated calcium channels of the uterus or were mediated by extra-uterine mechanisms, the potency of nifedipine as a relaxant of uterine spasms in vitro was investigated. The potency of nifedipine in the isolated uterus as a relaxant of the spasm induced by KC1 did not differ between rats which received oestrogen, progesterone or oestrogen plus progesterone or corn oil. Additionally, the potency of nifedipine to inhibit oxytocin-driven phasic tension development was not affected by treatment with oestradiol. These findings suggest that the increase in potency and maximum effect of nifedipine against uterine contractions observed previously in rats in late pregnancy can be ascribed, in part, to the action of the ovarian steroids (oestrogen and progesterone). The increase in potency of diltiazem observed in rats in late pregnancy, however, is due to factors other than oestrogen and progesterone. The lack of effect of hormonal manipulations on the potency of nifedipine on the isolated uterus suggests that the changes in potency in vivo due to oestrogen and progesterone are mediated by extra-uterine mechanisms. J. Endocr. (1988) 118, 251–258

Publisher

Bioscientifica

Subject

Endocrinology,Endocrinology, Diabetes and Metabolism

Cited by 11 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3