Effects of levorphanol on phospholipid metabolism and composition in Escherichia coli

Abstract

1. 1. The effects of growth inhibitory concentrations of the morphine analogue levorphanol on the metabolism and composition of membrane phospholipids were investigated in Escherichia coli. 2. 2. Incorporation of radioactive precursors into the total lipid fraction is reduced. 3. 3. During incubation with levorphanol there is a gradual rise in the proportion of radioactivity incorporated into cardiolipin, from 5% (untreated) to 55–70% after 60 min. In addition to the more rapid labeling of cardiolipin there is evidence for reduced breakdown of cardiolipin in the presence of levorphanol. 4. 4. The incorporation of precursors into phosphatidyl ethanolamine is markedly reduced. The turnover of phosphatidyl glycerol is accelerated and phosphatidyl ethanolamine, normally stable, exhibits turnover in the presence of levorphanol. 5. 5. After 1 h incubation with levorphanol the relative amounts of individual phospholipids, determined as phospholipid phosphorus, are 45% phosphatidyl ethanolamine, 10% phosphatidyl glycerol and 45% cardiolipin, as compared to 68% phosphatidyl ethanolamine, 25% phosphatidyl glycerol and 7% cardiolipin in untreated bacteria. 6. 6. In drug-free medium the phospholipid labeling pattern of cells labeled in the presence of levorphanol slowly reverts towards normal. 7. 7. Possible relationships between the observed alterations in phospholipid metabolism and composition and the effects of levorphanol on transport and on ribosomal RNA synthesis are discussed.