The Mechanism Of Estradiol On The Activity Of Duodenal Myoeletrical Activity In Female Rabbit

Estrogen is a class of ovarian hormones with a wide range of biological activities.It not only promotes the development of reproductive organs such as female ovaries,uterus,fallopian tubes,and vagina and maintains female secondary sexual characteristics,but also participates in the regulation of digestion,respiration,and cardiovascular systems.Estrogen has a very significant regulatory effect on the gastrointestinal motility,but the reported effects of regulation are not exactly the same.So how does estrogen regulate the duodenal movement?In this study,the double immunofluorescence labeling method was used to detect the expression and distribution of the estrogen receptors ERα,ERβand cholinergic transmitter M₂mAChR in the duodenum of female rabbits.The BL-420F biological functional test system was used to observe and analyze the effects of estradiol benzoate and cholinergic receptor agonists（carbachol chloride）and antagonists（atropine sulfate）on duodenal myoelectric activity.Meanwhile,the data obtained was used to establish the mathematical function.The main results of this experiment are as follows:1.The result of immunofluorescence double labeling showed that both the ERα,and M₂mAChR or the ERβand M₂mAChR were double-labeled in the duodenum of female rabbits.The double-labeled positive products of ERαand M₂mAChR were mainly distributed in the mucosal layer and submucosa of the duodenum,and were slightly distributed in the muscular layer.The double-labeled positive products of ERβand M₂mAChR were mainly distributed in the mucosa and submucosa of the duodenum.2.The effect of estrogen on the duodenal myoelectric activity showed that the amplitude,frequency,and myoelectric activity index of the duodenal smooth muscle in the ovariectomized group’s rabbits and the ovariectomized+ICI187280 group’s rabbits were all significantly lower than those in the control group which are not conducted by ovariectomy（P<0.01）.Whereas there was no significant difference in the above-mentioned monitoring indicators between the ovariectomized group and the ovariectomized+ICI187280group（P>0.05）.These results indicating that the influence of endogenous ovarian hormone sholud be eliminated by ovariectomy in the study of the effect of estrogen on the duodenal myoelectric activity.3.After treatment with different doses of estradiol benzoate in ovariectomized female rabbits,the amplitude,frequency and the index of myoelectric activity of duodenal myoelectricity contented increase first,and then decrease with the increase of estradiol benzoate dose.The functional model of the relationship between the dose of estradiol and the index of myoelectric activity was established through the analysis and screening of each monitoring index,the expression is:y=1.50+3.73×exp{-0.5×[（x–0.098）/0.035]²},of which“y”means the index of myoelectric activity and“x”means dose of estradiol benzoate.The analysis of this function showed that the index of myoelectric activity ranged from 1.50mV·min^-1 to 5.23 mV·min^-1,and the maximum value reached 5.23 mV·min^-1 when the dose of estradiol is 0.098 mg·kg^-1.In addition,the dose of estradiol were 0.063 mg·kg^-1,0.098mg·kg^-1,0.133 mg·kg^-1 as the cutting point,the trend of the index of myoelectric activity with the increase of estradiol dose was divided into exponential increase,logarithmic increase,exponential decrease and logarithmic decrease.4.After administrating by atropine sulfate in rabbits pre-treated with different doses of estradiol benzoate to completely block the innervation of cholinergic nerves in the digestive tract,the amplitude,frequency,and myoelectric activity of the duodenal electrical activity were all strongly inhibited,and the concentration-dependent regulation of estrogen on the duodenal myoelectric activity also disappeared.However,after administrating by different doses of carbamylcholine chloride in rabbits pre-treated with different doses of estradiol benzoate to enhance the innervation of cholinergic nerves in the digestive tract,the concentration-dependent regulation of estrogen on the duodenal myoelectric activity was appeared again in administrated by any dose of carbamylcholine chloride.By estabilshing the functional model of the relationship between the dose of estradiol and the index of myoelectric activity with the administration of different dose of carbamylcholine chloride and analyzing and comparing the characteristics of parameters in the same position of each funcion including the function established by the effect of estrogen alone on the duodenal myoelectric activity,the expression of the function of combined action of estradiol benzoate and carbachol chloride was comfirmed:f（x,y）=5.11/{1+exp[-52.84×（y–0.016）]}+[3.82+2.40×exp{-exp[-（y–0.042）/0.008]–（y–0.042）/0.008+1}]×exp{-0.5×[（x–0.098）/0.034]²},of which“f（x,y）”means the index of myoelectric activity,“y”means dose of carbamylcholine chloride and“x”means dose of estradiol benzoate.It can be seen from this function that under the influence of different dose of carbamylcholine chloride,the dose of estradiol benzoate that have the highest and the inflect effect on the myoelectric activity index were not changed,that is,the dose of estradiol could still be 0.063 mg·kg^-1,0.098 mg·kg^-1,0.133 mg·kg^-1 as the cutting point,the trend of the index of myoelectric activity with the increase of estradiol dose was divided into exponential increase,logarithmic increase,exponential decrease and logarithmic decrease.However,the lowest effect of estradiol benzoate on the duodenal myoelectric activity index and the peak effect of change in the myoelectric activity index were continuously changing under the increase in the dose of carbachol chloride.The former was enhanced with the increase of carbachol chloride while the latter was went through a change in the trend of increase at first and then decrease with a critical limitation of 0.042 mg·kg^-1 in the dose of carbachol chloride.The above results indicate that the effect of estrogen on the duodenal movement is achieved through an indirect pathway that acts on the cholinergic nerves innervating in the duodenum.The estrogen can regulate the visceral function through the influence of the neural reflex arch innervating in the visceral organ.