Distribution of mitochondria in normal and hypertrophic myocytes from the rat heart.

The spatial distribution of mitochondria in myocytes from two regions of normal hearts and hearts hypertrophied due to renal hypertension was analyzed. First, the cross-sectional area of myocytes on electron micrographs was divided into two approximately equal portions with respect to the closest capillary wall. Volume density of mitochondria was then determined in both portions by the point counting method. Similarly, the cross-section of myocytes was divided into approximately equal parts with respect to the cell surface and evaluated as above. Analysis of variance revealed that the volume density of mitochondria was significantly higher in tissue portions close to the capillary wall and cell surface than in the remaining tissue (31.6% and 31.1% v. 26.2% and 26.1%, P less than 0.01) and P less than 0.05). No significant differences between subepicardial and middle regions were found. We conclude that there is a preferential distribution of mitochondria with respect to cell surface and capillary wall; the gradient, however, is much smaller than some 'typical' illustrations may imply.