Metabolic characterization of mouse bone marrow cells responsive to estrogenic inhibition: hexose monophosphate shunt enzyme activity in enriched populations of mature cells and progenitor cells.

Compounds with estrogenic activity cause initial toxic responses in the bone marrow characterized by hypocellularity and stem cell myelotoxicity. To elucidate the biochemical nature of these toxic responses, bone marrow cells were collected from mice treated with pharmacological doses of estrogenic chemicals, separated into enriched cell populations, and the enzymatic responses of the individual cell types characterized. Female B6C3F1 mice were injected s.c. with five daily doses of 0.07-5.6 mu moles diethylstilbestrol (DES) or 17-beta estradiol. At 4 days posttreatment body and organ weights were recorded and bone marrow was collected for enumeration and assay of stem cell proliferative responses and enzyme analyses. Treatment with higher dose levels of either estrogenic chemical caused equivalent thymic atrophy, but DES resulted in greater liver and spleen hypertrophy than estradiol. Hexose monophosphate shunt dehydrogenase enzymes in unfractionated bone marrow cells were more sensitive to inhibition by lower estrogen doses than representative enzymes from glycolysis of the Kreb's Cycle, and on an equimolar basis were inhibited to a greater extent by DES than by estradiol. Enzyme analyses after density gradient cell separation indicated that 70-80% of the hexose monophosphate shunt enzyme activity in bone marrow from untreated mice occurred in the enriched band of cells containing predominantly granulocyte-macrophages. The majority of the enzyme inhibition induced by DES treatment could also be ascribed to this cellular population. Furthermore, it was shown that DES had a greater inhibitory effect on the proliferative capacity of the committed stem cells than on the multipotential stem cell population, and the main response was again expressed in the enriched band of cells containing predominantly granulocyte-macrophage precursors. Preliminary endocrine ablation experiments indicated estrogen inhibition of hexose monophosphate shunt enzyme activity was independent of the adrenal and the ovary, but was mediated through the thymus at lower estrogen concentrations.