To determine the ventricular looping pattern in relation to cardiac laterality, we studied rat embryos treated with retinoic acid (RA). A total of 243 Wistar rat embryos from an in vivo treated group (a single dose of 20-40 mg/kg all-trans RA administered to pregnant rats on day 6.5 to 9.5) and 29 control embryos were examined on day 13 of gestation. Twenty-nine embryos from the in-vitro treated group (treated by all-trans RA at 2 x 10(-7) M for 6 hr on day 9.0 or 9.5 during the entire embryo culture for 72 hr) and seven control embryos were examined on day 12 of gestation. Abnormalities in cardiac laterality and ventricular looping were found in the in-vivo groups treated on day 8.5 and 8.75 and in the in-vitro group on day 9.0. Among 25 animals with abnormal laterality, right isomerism was the most common feature (22 cases), while the type of ventricular looping varied. Cases with normal laterality had a low incidence of abnormal looping (1.4%). In rat embryos treated with all-trans RA, normal cardiac looping was expected when cardiac laterality was normal. But in cases with abnormal laterality, the type of abnormal ventricular looping was unexpected.
Animal ; Cell Division ; Female ; Heart/drug effects* ; Heart Defects, Congenital/pathology ; Heart Defects, Congenital/chemically induced* ; Heart Ventricle/pathology ; Heart Ventricle/abnormalities* ; Incidence ; Male ; Pregnancy ; Rats ; Rats, Wistar ; Tretinoin/pharmacology*

Chlorinated solvents are recognized as well-known drinking water contaminants and potent teratogens for developing embryos. Among theses compounds, tetrachloroethylene was studied to evaluate the teratogenic effects in detail. This study was also undertaken to understand the teratogenetic mechanisms by assessing the relationship between the physiological impairments and cellular degeneration including apoptosis induced by tetrachloroethylene, and the cardiovascular malformations. Fertilized white leghorn eggs (n=530) were incubated for 90~96 hours up to Hamburger-Hamilton stage 27~28. To the experimental group, tetrachloroethylene was dissolved in mineral oil at concentrations of 40 micrometer and 50 micrometer and was injected into the chorioallantoic membrane. One half of the control was injected with saline and the other half with mineral oil. The experimental animals are studied for ECG changes, and light and electron microscopic observation. Two silver thread electrodes were used to record the ECG. ECG changes were recorded for 6~30 minutes after tetrachloroethylene injections. In parallel studies, blood velocity through the dorsal aorta was measured by a pulse Doppler velocity meter with 20 MHz probe. The specimens were stained with hematoxylin and eosin for light microscopic study and the Hitachi H-800 EM was used for transmission electron microscopic evaluation. The embryos underwent formalin fixation on day 14, and the presence of malformations was observed by a microscopy. The results obtained are as follows: Repeated injections of 40~50 micrometer tetrachloroethylene appeared to have a strong influence on the formation of cardiovascular malformations. Various types of cardiac malformations were observed in the experimental group compared to control group, that were statistically significant (p<0.01) and many embryos also died. The malformations observed were large ventricular septal defect, endocardial cushion defect, double outlet right ventricle and truncus arteriosus associated with single ventricle. Large ventricular septal defect was most common type of cardiovascular abnormalities. Arrythymias including ventricular fibrillations were evident on ECG 6~30 minutes after the injections. Blood flow through the dorsal aorta was markedly decreased in concordance with the ECG changes. A large amount of individual cell death suggesting apoptosis was seen on light microscopic evaluation and the electron microscope revealed cellular degeneration of the embryonic myocardium. We concluded that tetrachloroethylene, like other chloride compounds has potent teratogenic effects. The cardiac malformations were probably caused by decreased blood flow due to physiofunctional changes and cellular necrosis associated with apoptosis. By including birds and mammals in further experiments, we hope to elucidate an embry-ological clue into how early cardiovascular malformations are caused.
Animals ; Aorta ; Apoptosis ; Birds ; Cardiovascular Abnormalities ; Cell Death ; Chick Embryo* ; Chorioallantoic Membrane ; Double Outlet Right Ventricle ; Drinking Water ; Eggs ; Electrocardiography ; Electrodes ; Embryonic Structures ; Endocardial Cushion Defects ; Eosine Yellowish-(YS) ; Formaldehyde ; Heart Septal Defects, Ventricular ; Hematoxylin ; Hope ; Mammals ; Microscopy ; Mineral Oil ; Myocardium ; Necrosis ; Ovum ; Silver ; Solvents ; Teratogens ; Tetrachloroethylene* ; Truncus Arteriosus ; Ventricular Fibrillation