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Pyridine Nucleotide-linked Dehydrogenases and Isozymes of Normal Rat Breast and Growing and Regressing Breast Cancers¹

Department of Surgery, Washington University School of Medicine, St. Louis, Missouri, and the Beatrice F. and Melville N. Rothschild Surgical Research Laboratories, Michael Reese Hospital and Medical Center, Chicago, Illinois

Four pyridine nucleotide-linked dehydrogenases, glucose-6-phosphate dehydrogenase (G6PDH),³ isocitric dehydrogenase (ICDH), lactic dehydrogenase (LDH), and malic dehydrogenase (MDH), and their isozymes have been studied in the normal virgin rat breast, in the breast of tumor-bearing rats, in the breast cancers themselves, and in these tissues following ovariectomy. Enzyme activity expressed per mg DNA-P facilitates comparison of tumor and normal cells. In breast cancer, the total LDH and G6PDH activity increased, MDH activity decreased, and the proportions of LDH and MDH isozymes were altered. The Kaplan M type of LDH isozyme (2) is more prominent in tumors. Ovariectomy resulted in regression of tumor size accompanied by decrease in total G6PDH and LDH activity but did not restore to normal the proportions of LDH or MDH isozymes.

¹ Supported by the American Cancer Society, Grant T 59, and the USPHS, Grant RG 4431.

³ Abbreviations used are: G6PDH, glucose-6-phosphate dehydrogenase; ICDH, isocitric dehydrogenase; LDH, lactic dehydrogenase; MDH, malic dehydrogenase; DNA-P, deoxyribonucleic acid phosphorus; 3-MC, 3-methylcholanthrene; NAD, nicotinamide adenine dinucleotide; and NADP, nicotinamide adenine dinucleotide phosphate.

² Present address: Department of Surgery, Michael Reese Hospital and Medical Center, Chicago, Ill.

Received 5/ 5/65. Revised 8/25/65.