Lactate Dehydrogenase Isoenzymes in the Diagnosis of Human Benign and Malignant Brain Tumors2

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Abstract
The changes in isoenzyme distributions of lactate dehydrogenase and calculated ratios of heart muscle (H)/skeletal muscle (M) were studied by means of agar gel enzymoelectrophoresis in 161 extracts from 43 primary, human malignant gliomas, 14 metastases, and 28 oligodendrogliomas and astrocytomas. The isoenzyme patterns were compared to those obtained from normal human brain regions. More than 95% of all determinations of “average” normal brain fell within the range of H/M 1.5–2.6 combined with relative M4 activities below 3.9%. H/M ratios above 4.6 combined with a relative M4 activity below 2% indicated an oligodendroglioma. H/M ratios above 2.6 with M4 activities below 2% showed a mixed oligodendroglioma or astrocytoma. An H/M ratio above 4.6 combined with a relative M4 activity above 2% indicated malignancy in an oligodendroglioma. H/M ratios above 2.6 with relative M4 activities above 2% demonstrated malignancy in an area of gliosis. H/M ratios below 1.5 indicated a malignant glioma or a metastasis. H/M ratios below 1.0 suggested a histological grade of malignancy corresponding to Kernohan 3–4.