Submitted on July 18, 2008
Revised on February 2, 2009
Accepted on February 23, 2009
Estradiol Upregulates the Expression of Oxytocin Receptor in Colon in Rats
Mei Feng1, Jun Fang Qin1, Chao Wang1, Yanfang Ye1, Shuanglian Wang1, Dong Ping Xie2, Paulus S. Wang3, and Chuanyong Liu1*
1 Medical School of Shandong University
2 Medical School of Shadnong University
3 National Yang-Ming University
* To whom correspondence should be addressed. E-mail: liucy{at}sdu.edu.cn.
The study was designed to investigate the effect of estradiol (E2) on the excitatory effect of oxytocin on colon motility. Female Wistar rats were used and some of them were ovariectomized (OVX) and treated with E2. A plastic balloon made of condom was inserted into colon in order to monitor the change of colonic pressure in vivo. Longitudinal muscle strips of distal colon were prepared to monitored the spontaneous contraction of colon in vitro. Expression of oxytocin receptor (OTR) was investigated by Western blot analysis. Expression of OTR mRNA was detected by RT-PCR. Immunohistochemistry was used to locate OTR. In OVX rats, pretreatment of E2 (4-100 µg kg-1, s.c.) dose dependently increased the excitatory effect of oxytocin on colon motility both in vivo and in vitro, and increased the expression of OTR and OTR mRNA in colon. Systemic administration of OT excited the colon motility in vivo in rats at period of proestrus and estrus, but did not influence it at diestrus period, when the concentration of plasma E2 was lowest in the estrus cycle. Pretreatment of atosiban, the specific OT receptor (OTR) antagonist, and TTX, the blocker of voltage dependent sodium channel on nerve fiber, attenuated the excitatory effect of OT on colon motility. OTR was located in myenteric plexus of colon. These results suggested that E2 increased the excitatory effect of OT on colon motility by upregulating the expression of OTR in myenteric plexus.
