Concentrations In Maternal Plasm And Action Of CRH,CORT SP Before And After Introduced Abortion

Although a number of the key hormones and proteins involved havebeen identified, what leads onset of labor remains unclear.It requires that theuterus, which has been maintained in a relative state of quiescence duringpregnancy, develops coordinated contractility and that the cervix dilates in amanner that allows passage of the fetus through the birth canal and maturationof those fetal organ systems necessary for extrauterine survival hasoccurred.The function of fetal HPA axis and onset of labor are regulated by manyneuroendrocrine regulators,including corticotrophin-releasing hormone(CRH), cortisol(CORT) and substance P(SP).The aim of this study was to examine concentrationchange and action of CRH,CORT and SP in maternal plasm on induced abtortion.CRH,CORT and SP concentrations in plasm were measured byradioimmunoassay in 48 women who were undergone induced abtortion.Beforeinduced abtortion,they were samped and were divided into four groups :Group Ainduced abtortion with mifepristone and misoprostol(n=6), Group B inducedabtortion with rivanol(n=17),Group C induced abtortion withmifepristone and rivanol(n=18),Group D induced abortion with water balloondevice (n=3).After induced abortion, they were divided into two groups:GroupX sampling as cervix dilatation on 3cm(n=21),Group Y sampling asbirth(n=23).The results show that CRH concentration in plasm was7.577±1.726 ng/ml before induced abortion and 11.788±4.018ng/ml afterinduced abortion.P values below 0.01.SP concentration in plasm was62.292±21.822 ng/ml before induced abortion and 74.951±24.542ng/ml afterinduced abortion.P values below 0.05.CORT concentration in plasm was210.373±72.481ng/ml before induced abortion,and248.063±73.838ng/ml after induced abortion , P values below 0.05.Theconcentrations of CRH in maternal plasm were gradually increased afterlabor(P<0.05).CORT paralleled with that before induced abortion(r=0.354,P<0.05). We can conclusion that induced abtortion was associated withincreased maternal plasm CRH,CORT and SP concentration. CRH playedan important role in the onset of induced abortion.Placental production ofCRH is proposed as an early event regulating the cascade of events of labor.The concept of placental CRH as"a placental clock controlling the length ofhuman pregnancy"implied a stimulus effect on the myometrium,which isdifficult to reconcile with the known biochemical effects of CRH. CRHexerts its effects through activating specific G protein coupled receptors,which exist in two subtypes: CRH-R1 and CRH-R2. CRH increases fetal ACTHexpression ,leading increasing of fetal adrenal gland cortisol which leading fetusdevelepment and maturation,translating pregnenolone into C19 steroids includingdehydroepiandrosterone (DHEA) and androstenedione , and in placentaconversion of DHEA to estrogen which is taking part in labor onset.CORT output byfetal adrenal gland,on the contrary,contributes to a feed-forward loopinvolving elevation of CRH production from intrauterine tissues.CORT bindsto glucocorticoids receptors by competing with progesterone,whichleading"functional pregesterone withdrawal.CRH and CORT increases PGHSexpression,activity and decreases PGDH activity,which leads PG increase ofintrauterine tissues,on the contrary,contributes to a feed-forward loop involvingelevation of CRH and CORT production.CRH increases oxytocin receptors expressionof intrauterine tissues,and triggers cervical ripening.At last,labor starts.Prior to parturition the non-pliable uterine cervix undergoes a ripeningprocess ("softens" and dilates) to allow a timely passage of the fetus atterm.The exact mechanism triggering and involved in cervical ripening isunknown, though evidence for a role for sensory neurons and theircontained neuropeptides is emerging.An apparent increase inneuropeptide immunoreactive nerves occurs in the cervix duringpregnancy, maternal serum estrogen levels rise at term and uterinecervix-related L6-S1 dorsal root ganglia(DRG) sensory neurons expressestrogen receptor (ER)and neuropeptides.The neuropeptide SP changesbiosynthesis and release over pregnancy, that estrogen, acting via the ERpathway, increases synthesis of SP in DRG, and that SP is utilized in cervicalripening at late pregnancy. In our study,induced abtortion was associatedwith increased maternal plasm SP concentration,so we postulated that SPmay play a role in cervical ripening and,consequently in the birth process.