| Objective:By observing the effects of arsenic exposure in female SD rats before and during maternal pregnancy on the development of cardiac morphology and structure of fetal rats, we discuss the relationship between maternal arsenic exposure and the incidence of congenital heart disease(CHD) in the offspring. By detecting m RNA and protein expression levels of heart development key gene Nkx2.5, GATA-4 and TBX5 within the fetal heart tissue, we discuss the possible pathogenic mechanism to provide a scientific basis for the study on the mechanism of CHD.Methods:According to body weight, 60 female SD rats(30 to 40 days of age) were randomly divided into a control group and five arsenic exposure group with 10 rats per group. They were allowed free access to drinking water with 0, 9.4, 18.8, 37.5, 75 and 150 mg/L of sodium arsenite(A, B, C, D, E, F group)respectively. Continuous infected 6 weeks, all the female rats and adult male SD rats were caged overnight for mating, and females were examined for a vaginal plug and sperm in the vaginal smear in following morning. If a vaginal plug and(or) sperm were observed, it was considered as a succesful pregnancy. The pregnant mice were given their original arsenic concentration until the embryonic day 16. On embryonic day 16, rats were sacrificed to harvest fetuses. We record the number of live births, dead and absorption. Embryo and placenta were weighted to assess the effects of arsenic exposure on the development and growth of fetal rats. The fetal heart tissue was continuously sliced. Cardiac morphology and structure was detected with hematoxylin-eosin staining under a microscope. The protein and m RNA expression levels of Nkx2.5, GATA-4 and TBX5 factor within the fetal heart tissue were analyzed by western blotting assay and real-time polymerase chain reaction. The changes of fur arsenic contents of female rats were determined with the method of atomic fluorescence spectrometry.Result:1. With increasing concentrations of arsenic in drinking water, fetal weight, placental weight, mean nidation fetus and live fetus per litter increased, and the incidence of fetal absorption decreased. There were statistical differences compared both fetal weight and placental weight in group C, D, E and F with these indicators in group A(P<0.05). There were statistical differences compared both mean nidation fetus and live fetus per litter in group F with that in group A(P<0.05). There were statistical differences compared the incidence of fetal absorption in group D, E and F with that in group A(P<0.05).2. Cardiac malformations in some fetal rats including ventricular septal defect, atrial septal defect and pulmonary stenosis were observed in group D, E and F. The incidence of cardiac malformations was 0%, 0%, 0%, 7.4%, 23.8% and 38.1% in group A, B, C, D, E and F, respectively. There were statistical differences compared the incidence of cardiac malformations in group E and F with that in group A(P<0.05).3. Compared with group A, the m RNA relative expression levels of both Nkx2.5 and GATA-4 factor within the fetal heart tissue significantly decreased in group C, D, E and F(P<0.05). Compared with group A, the m RNA relative expression levels of TBX5 factor within the fetal heart tissue increased in group B and C(P<0.05) and significantly decreased in group D, E and F(P<0.05).4. Compared with group A, the protein relative expression levels of Nkx2.5 factor within the fetal heart tissue significantly decreased in group D, E and F(P<0.05). Compared with group A, the protein relative expression levels of GATA-4 factor within the fetal heart tissue significantly decreased in group B, C, D, E and F(P<0.05). Compared with group A, the protein relative expression levels of TBX5 factor within the fetal heart tissue increased in group B and C(P<0.05) and significantly decreased in group D, E and F(P<0.05).5. There were statistical differences compared fur arsenic contents of female rats detected on the last exposure day in group B, C, D, E and F with that in group A(P<0.05).Conclusion:1.Arsenic exposure before and during maternal pregnancy can inhibit the growth and development of embryos, having embryonic developmental toxicity. Embryonic developmental toxicity includes reducing fetal weight, placental weight, mean nidation fetus and live fetus per litter, and increasing the incidence of fetal absorption.2. Arsenic exposure before and during maternal pregnancy can cause abnormal cardiac morphology and structure in fetal rats, which includes ventricular septal defect, atrial septal defect and pulmonary stenosis. Maternal arsenic exposure can increase the risk of CHD in the offspring.3. Arsenic exposure before and during maternal pregnancy can inhibit the expression of both m RNA and protein of Nkx2.5, GATA-4 and TBX5 factor within the fetal heart tissue, which suggests that arsenic exposure may change m RNA expression levels of Nkx2.5, GATA-4 and TBX5 factor by a certain mechanism, subsequently down-regulating the expression levels of the coding protein and ultimately leading to downstream morphological abnormalities, namely CHD.4. Fur arsenic contents of female rats detected on the last exposure day increased with the increase of Na As O2 concentrations. This suggests that fur arsenic contents can reflect the levels of maternal arsenic load to some extent. When the concentration of Na As O2 was greater than or equal to 75mg/L, the incidence of CHD in fetal rats was significantly increased, and compared with the control group, fur arsenic contents of female rats were significantly different. This indicates that maternal arsenic load reaching a certain level will increase the risk of CHD in the offspring. |
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