N2O-induced hypoxia as a model of hypoxic stress of ratmyocardium. An ultrastructural — morphometric study

Summary A model system consisting of a hypoxia chamber combinedwith a commercial narcosis apparatus adapted to small animals was used to perform a controlled acute isobaric hypoxia on rats with N 2 O/O 2 . Ultrathin sections from the left ventricular wall were analysed qualitatively and quantitatively using a computer-aided morphometric program. Compared with the control the cardiomyocytes exhibited a significant increase of volume densities of cytoplasmic vacuoles, lipid drops, sarcoplasmic reticulum, mitochondria, and degenerated intramitochondrial areas. Hypoxic alterations of microvessels consisted mainly in localized endothelial swelling and perivascular edema, protrusions of the luminal surface and moderate mitochondrial alterations similar to those of cardiomyocytes. Further, the number of plasmalemmal vesicles decreased, and the number of vacuoles increased significantly. The results were confirmed by quantitative histochemistry performed by our group in a parallel study. The model can be recommended for studies concerning protective interventions in hypoxia experiments.