Methylmercury Toxicity During Heart Development: A Combined Analysis of Morphological and Functional Parameters

The heart of higher vertebrates develops early as a tubular structure, which requires cellular and molecular events for proliferation, differentiation and apoptosis for growth, and individualization of cardiac chambers. Exposure to different stressors can cause disturbances in the normal development and functionality of the cardiovascular system. This study aimed to characterize the impact of methylmercury (MeHg) on heart development, specifically related to tissue morphology and parameters of vascular integrity and contractility, also focusing on cell cycle and apoptosis, using Gallus domesticus embryos as a model. The results showed morphological alterations, reduction in the thickness of the ventricular walls, and trabeculae changes in the hearts of embryos exposed to 0.1 µg MeHg/50 µL saline solution. These impacts were associated with increased contents of proteins related to cell cycle arrest and reduced cardiomyocyte proliferation. In addition, the contents of endothelial mediators for contractility and vascular integrity were imbalanced. The quantity and morphology of mitochondria of cardiomyocytes were injured. Together, these negative measurements impacted the reduction of heartbeats. In general, the parameters identified here demonstrate the relevance of combined molecular cellular tissue and physiological diagnosis for a better understanding of the cardiotoxicity of MeHg during development.