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Lactate Dehydrogenase Isoenzymes in Tissues of Normal and Ehrlich-Lettré Ascites Tumor-bearing Swiss Mice¹

Department of Biological Chemistry, UCLA School of Medicine, Los Angeles, California 90024

This study characterizes the lactate dehydrogenase (LDH) isoenzyme electrophoretic patterns and total activities of brain, heart, kidney, liver, lung, skeletal muscle, small intestine, spleen, testes, and ventral abdominal wall in healthy Swiss mice and in mice with advanced Ehrlich-Lettré ascites tumor. In addition, the total LDH activity and isoenzyme patterns of the ascites tumor cell itself and of its subcellular fractions were investigated. The LDH isoenzyme patterns of mouse tissues are quite different and migrate more anodally at pH 8.6 than do the LDH isoenzymes of other animal species. Several of the tissues from mice, especially liver, spleen, and erythrocytes, have more LDH₅ (subscripts represent isoenzymes, with negativity increasing with decreasing value of subscript) than do these tissues from other animals. Erythrocytes have LDH₅ almost exclusively. The testes have a high percentage of LDH_X. Liver, spleen, and testes from tumorous mice have more total LDH and abdominal wall has less LDH than do the same tissues from control mice. The tumor cells have a large complement of LDH, mostly LDH₅, with small amounts of LDH₄ in the mitochondria. Liver cell mitochondria and microsomes also have mostly LDH₅, with small amounts of LDH₄ and even less of LDH₃ and LDH₂. Relative thermal stability determinations on the isoenzymes in kidney and heart showed LDH₅ and LDH₁ to be the most stable, with LDH₄, LDH₂, and LDH₃ being somewhat less stable.

¹ This investigation was supported by Grant-in-aid 2 RO1 CA-02006-15 from the National Cancer Institute, USPHS.

Received 12/11/68. Accepted 9/19/69.