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Isozymes of Lactate Dehydrogenase during Beryllium Carcinogenesis in the Rat¹

Department of Occupational and Environmental Health, School of Medicine, Wayne State University, Detroit, Michigan 48207

Starch gel zymograms of lactate dehydrogenase in the pulmonary tissue extract of rats exposed daily to the inhalation of BeSO₄ aerosol showed well-defined differences in comparison to paired controls. Significant increase of both the muscle-type and heart-type isozymes was observed during the immediate precancerous phase (8th–10th month of exposure), followed by return to normal or subnormal levels at the time of appearance of the fully grown pulmonary tumors (12th–13th month). H₄-lactate dehydrogenase (LDH), but not M₄-LDH, was significantly depressed in tumor tissue both in comparison to controls or to the nonneoplastic parts of the exposed lungs. Since beryllium salts inhibit the activity of LDH in vitro, these results show that a reversal of the direct effect takes place during the malignant transformation, followed in part by a second reversal during tumor growth.

¹ This research was supported by Grant # E-253 I of the American Cancer Society.

Received 3/17/67. Accepted 6/15/67.