Examination of the heart is routinely included in toxicologic evaluation. In NTP studies, the heart is sectioned through the longitudinal axis, to include the right and left ventricles, interventricular septum, both atria, and a portion of the major vessels at the base of the heart.
The muscular chambers are composed of three layers: the epicardium, the myocardium, and the endocardium.
Damage to the heart may be either structural or functional. Structural abnormalities may be detected microscopically, whereas functional changes are typically assessed through other means, such as enzyme detection or blood pressure measurements. Differentiating spontaneously occurring lesions from treatment-related lesions may be difficult. Spontaneous cardiomyopathy is commonly found in rats but less commonly in mice. Further, some spontaneous lesions may be exacerbated by treatment, making differentiation even more difficult.
Jokinen MP, Boyle M, Lieuallen WG, Johnson CL, Malarkey DE, Nyska A. 2011. Morphologic aspects of rodent cardiotoxicity in a retrospective evaluation of National Toxicology Program studies. Toxicol Pathol 39(5):850-860.Abstract: https://www.ncbi.nlm.nih.gov/pubmed/21747121
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