Effect of heme depletion on growth, protein synthesis and respiration of murine erythroleukemia cells

Abstract

4,6-Dioxoheptanoic acid (succinylacetone, SA) profoundly inhibits δ-aminolevulinic acid (ALA) dehydratase, the second enzyme of the heme biosynthetic pathway. When murine eyrthroleukemia (MEL) cells were grown in defined medium containing 0.3–1.0 mM SA and gelatin as the protein source, cellular heme concentrations decreased markedly and growth was inhibited. Growth inhibition was partially reversed when hematin (300 pmoles/ml) was added with SA on day 0, but no reversal of growth inhibition was seen when this concentration of hematin was added on day 4. Complete reversal of growth inhibition produced by 0.3 mM SA occurred when hematin was added in concentrations of 1–2 nmoles/ml on day 0. Cellular heme content and growth rates indicate that exogenously added hematin was taken up from defined medium containing only gelatin as the protein component. The decrease of cellular heme concentration was accompanied by a decrease of protein synthesis, which, like growth inhibition by SA, was partially reversed by addition of hematin to the medium. Although no significant impairment of endogenous cellular respiration was observed in these studies, there was a decrease in NADH-stimulated oxygen consumption in heme-depleted cells, suggesting diminished respiratory reserve in these cells.