The effect of methotrexate (MTX) on the small intestine of the mouse. III. Mitochondria and succinic dehydrogenase (SDH).

The effect of the cytotoxic agent MTX on the mitochondrial content and on SDH activity in the jejunal mucosa of mice was studied. The control epithelium contained variable quantities of mitochondria, in the form of granules, short rods and filaments. In the crypt cells these organelles were larger than in the villus cells. The concentration of mitochondria close to the brush border and the basement membrane is indicative of their importance in production of the energy needed for active transport across the plasma membrane. After MTX treatment, there was a general decrease in the number, size and stainability of the mitochondria. In the control, SDH activity was moderate and its localization coincided topographically with the distribution of the mitochondria. The decrease in SDH activity after MTX, correlated to the decrease in the mitochondrial content, might be due to mitochondrial damage resulting form the indirect effect of MTX.