Histostereological Teratogenic Effects of Phenytoin on the Fetal Heart and Vascular Tunics in Albino Rats (Rattus Norvegicus)

Abstract

Studies have shown that the normal morphogenesis of fetal heart and the vascular tunics is perturbed by in-utero exposure to anticonvulsants such as phenytoin when used during pregnancy. However, the histo-stereological teratogenic effects of phenytoin on the heart and vascular tunics development is not well understood. The broad objective of the current study therefore was to evaluate the histomophorlogical and histo-stereological teratogenic effects of phenytoin on the fetal heart and vascular tunics following administration of varied doses of phenytoin at different gestational periods. This study was carried out in SAFARI animal house of JKUAT and a static-group controlled-experimental study design was adopted. A total of 30 Albino rat dams weighing between 200-250g from a pure colony were used. These 30 dams were randomly assigned into two study groups of 3 control and 27 experimental. The 27 rats in the experimental group were further subdivided into 3 groups of 9 rats each; LPG-31mg/kg, MPG-62mg/kg and HPG-124mg/kg. The 9 rats in each of the three dose groups were further sub-divided into three sub groups with 3 rats each according to the time of exposure; TM1, TM2, and TM3. All rats were fed with standard rodent pellets and water ad-libitum, while those in the experimental group also received phenytoin treatment. All rats were humanly sacrificed at GD20 then 3 fetuses with the lowest, median and highest weights from each rat selected and their hearts harvested, weighed and processed for histo-morphological and stereological analysis. Data was collected using structured and coded tally sheets, entered and stored in Microsoft excel, then exported to SPSS version 21. One-way Analysis of Variance (ANOVA), followed by Tukey’s post hoc tests were done and results expressed as mean ± standard error of the mean (SEM) for all values. All results with p < .05 were considered to be statistically significant. The findings on the placental and fetal weights, CRL, BPD and the HC show statistical significant reduction (p < .05) among phenytoin treated groups compared with the control. On the histomorphological effects, it was established that the fetal heart left ventricular wall layers were distorted and that of the vascular tunics showed reduction in wall thickness among phenytoin treated groups. On the stereological findings, there was significant reduction p = .001 in total heart volume in phenytoin treated groups particularly at TM1 high dose group (311.40±10.4) when compared to that of the control (378.13±4.57). In conclusion, phenytoin has teratogenic histomorphological and stereological effects on the fetal heart and vascular tunics particularly when administered in TM1 and TM2 HPG and its teratogenicity is both dose and time dependent. The study recommends that high dose phenytoin use during pregnancy should be avoided particularly in the first trimester that presents the window of opportunity to its teratogenic effects on the cardiovascular development. Further studies also need to be carried out with higher primates in order to determine phenytoin dose rationalization and its application during pregnancy.