THE EFFECT OF HUMORAL FACTORS RELEASED BY HYPOPERFUSED PLACENTA ON FETAL DEVELOPMENT

Simulation of hypoperfusion of the right uterine horn in rats on the 14 th day of pregnancy resulted in disruption of microcirculation in placentas of the left uterine horn, decrease of fetal weight and length as well as in fetal death after implantation. The obtained data complement the overall understanding of the pathogenesis of preeclampsia and placental insufficiency and create preconditions for development of new areas of creation of effective drugs for treatment and prevention of these pathologies.


Introduction
Preeclampsia is the most frequent disease of pregnant women and holds the first place among the reasons of maternal and perinatal mortality.The pathogenesis of this severe disease is still far from being understood completely.However in recent years many authors report a specific histological pattern at time of morphological examination of the placenta, i.e. disproportional development of the marginal area between the maternal and the fetal portions [1,21,24,28].There has been observed incomplete invasion of cytotrophoblast into the coiled artery of the uterus.In case of gestosis the level of alteration of the coiled arteries themselves does not reach the level specific to normal pregnancy [18,26,27].Increased distance between the coiled arteries and the chorionic villae as well as immaturity of the coiled arteries themselves induces trophoblast ischemia and the fetoplacental barrier permeability increase.
The produced humoral factors in response to ischemia as well as possibly to fetal antigens which passed through the fetoplacental barrier with the increased permeability after penetration into a maternal body encourage accumulation of asymmetric dimethylarginine (ADMA) in plasma, development of generalized endothelial dysfunction, secondary ischemic events and oxidative stress [5,6,7,14,15,16,16].Due to the above search of new medicinal preparations for treatment and prevention of preeclampsia which would have endothelioprotective, anti-ischemic and antioxidant activity becomes of great importance [1,5,11,12,23,25].However the information on the influence of the humoral factors released by the hypoperfused placenta on fetal development and healthy portions of the placenta in the available literature is rather scarce.In this connection the presented work was dedicated to research of fetal development and the state of placenta under the conditions of placental hypoperfusion modeling.
Research objective: To study the peculiarities of fetal development and the state of placenta under the conditions of hypoperfusion modeling in rats.

Research methodology
The experiment involved 20 white female Wistar rats with the weight of 250-300 g.In order to form groups of pregnant animals with the specific gestational age male rats (2 animals) were introduced into a cage with female rats (3 animals) for the period of 24 hours, at that the animals before the experiment were maintained in separate cages.After that the animals were caged in separate cages and after the Рус.Eng.

DOI: 10.18413/2500-235X-2015-1-4-39-44
RESEARCH RESULT: PHARMACOLOGY AND CLINICAL PHARMACOLOGY period of 14 days pregnancy was established by palpation under the ether narcosis conditions.Our experiments showed 30-40% of pregnancy event frequency.The pregnant rats were divided into the groups (n=10): Iintact; IIwith modeling of hypoperfusion in the right uterine horn on the 14 th day of gestation.A model of the uterine hypoperfusion as described by many authors (Ошибка!Источник ссылки не найден., Ошибка!Источник ссылки не найден., Ошибка!Источник ссылки не найден.)and modified by us was taken as a prototype.On the 14 th day of gestation 10 animals underwent surgery involving application of silver clamps on the right iliac artery (0.2 mm) and the right ovarial artery (0.1 mm).Thus we've ensured hypoperfusion only in the right uterine horn in contrast to the described prototype.
On the 21 st day of gestation in order to register the indices of systolic and diastolic blood pressure (SBP, DBP) catheterization of the right carotid artery of the anesthetized (chloral hydrate in the dose of 300 mg/kg) animals was performed, bolus dosing of pharmacological substances was carried out into the right femoral vein.There were performed vascular tests in order to determine endothelium-dependent and endothelium-independent vasodilatation along with calculation of an endothelial dysfunction coefficient (EDC) [9].
The study of the placental microcirculation was made with the aid of the equipment produced by «Biopac systems» company: a polygraph MP100 with a laser Doppler flowmetry module (LDF) LDf100C and a sensor TSD144.The LDF results recording was performed by means of the program Acqknowledge of 3.8.1 version, the values of microcirculation were expressed in perfusion units (PU) [2, 3, 4].NO-production function of endothelium was assessed on the basis of the data on the content of stable NO metabolites, i.e. nitrite ions (NOx) in blood plasma.For the purpose of determining fluid content in the greater omentum the same was weighted, dried at the temperature of 37 0 С within the period of 24 hours and weighed once again [8,13].

Results and discussion
Application of the clamps on the right iliac artery and the right ovarial artery did not resulted in the statistically significant change of the blood pressure and the endothelial dysfunction coefficient (Table 1).The animals in this group demonstrated decrease of the placental microcirculation from 452.4±27.16 to 204.4±14.30PU in the right uterine horn and to 309.0±15.80PU in the left uterine horn (p<0.05).No statistically significant change of diuresis, proteinuria and NO-synthesizing function of endothelium was observed in these animals.
Modeling of reduced blood flow in the placentas of the right uterine horn produced changes of ischemic genesis, i.e. there were observed extensive necroses and hemorrhages in the labyrinth zone, tissues dissection on the border between the placenta and the uterine wall (partial separation).
The comparative evaluation of the state of fetuses revealed reduction of the fetal weight and size as compared to the group of intact pregnant animals and post-implantation fetal death.18.66±5.66*L Note: SBP, DBPsystolic and diastolic blood pressure (mm hg); EDCendothelial dysfunction coefficient (c.u.); microcirculation in the placenta (PU); nitrite ions concentration (NOx); * -р < 0.05 as compared to the intact animals group; Rthe right uterine horn; Lthe left uterine horn.
Therefore the results of the carried out experiment give evidence of the absence of marked effect of the right uterine horn hypoperfusion on systemic hemodynamic values.The local changes in the right uterine horn are expected and in line with the literature data.The changes observed in the left uterine horn blood supplying vessels of which remain intact have the biggest importance.To all seeming the humoral factors released by the ischemic placenta of the right uterine horn [23] have local marked effect on the intact placenta vessels since they are the most sensitive.
On the basis of the obtained data in relation to the pathogenesis of development of preeclamsia and placental insufficiency it is possible to state with some degree of certainty that the areas of ischemic placenta may induce deterioration of morphological and functional state of its healthy areas due to the released humoral factors.The obtained data give opportunities for creation of medicines for treatment and prevention of the discussed pathology which would have new mechanisms of action.