Effect of estrogen administration on glucose 6-phosphate dehydrogenase and lactate dehydrogenase isoenzymes in rodent mammary tumors and normal mammary glands.

The isoenzymes of glucose 6-phosphate dehydrogenase (G6PD) and láclate dehydrogenase (LDH) were studied in R3230AC mammary adenocarcinomas and normal mammary glands of Fischer rats at various times during and after the administration of estradiol-17/3. Total activities of G6PD and LDH were elevated in response to treatment with estrogen; however, only certain isoenzyme species were increased by administration of the hormone. In both the R3230AC tumor and the mammary gland, only the faster-migrating G6PD isoenzyme (G6PD-2) was elevated during administration of estradiol-17/3, and its activity decreased after hormonal treatment ceased. The LDH isoenzyme pattern showed an increase in activity attributable to the predominantly muscle type isoenzymes (LDH-5, LDH-4). The hormone-induced increase in enzyme activities, expressed per mg DNA, was considerably greater than that attributed to cellular proliferation. These data indicate that, in both normal and neoplastic breast tissues, estrogens exert a discrete effect on these dehydrogenases.