Induction of 5-aminolaevulinate synthase by two- to five-carbon alcohols in cultured chick-embryo hepatocytes. Relationship to induction of cytochrome P-450.
The induction of 5-aminolaevulinate synthase and of cytochrome P-450 by short-chain aliphatic alcohols was compared in primary cultures of chicken-embryo hepatocytes. Isopropyl alcohol, isobutanol, pentan-1-ol and isopentanol alone caused up to a 4-fold increase in 5-aminolaevulinate synthase, whereas ethanol and propan-1-ol did not. Induction of the synthase by isopentanol was maximal at 8 h, and reached a plateau thereafter, whereas the activity induced by 2-propyl-2-isopropylacetamide continued to increase for 20 h. In the presence of 3,4,3',4'-tetrachlorobiphenyl, an inhibitor of haem synthesis at the uroporphyrinogen decarboxylase step, synergistic induction of 5-aminolaevulinate synthase was observed with all the alcohols except ethanol. Ethanol, but not isopentanol, decreased the extent of induction of 5-aminolaevulinate synthase by 2-propyl-2-isopropylacetamide and 3,4,3',4'-tetrachlorobiphenyl (50% decrease at 112 mM-ethanol). Total protein synthesis was not inhibited by ethanol in these cells. The composition of porphyrins was determined after treatment of cells with ethanol, isopentanol or 2-propyl-2-isopropylacetamide. Untreated cells, when incubated with 5-aminolaevulinate for 6 h, accumulated mainly protoporphyrin. However, when cells were pretreated with ethanol, isopentanol or 2-propyl-2-isopropylacetamide for 20 h, and 5-aminolaevulinate was added, 8- and 7-carboxyporphyrins increased, whereas protoporphyrin decreased. The dose responses for induction of either 5-aminolaevulinate synthase or cytochrome P-450 after a 20 h exposure to 3- to 5-carbon alcohols were identical. The results indicate that: simple alcohols can induce both enzymes; hydrophobicity increases their effectiveness; and induction of both enzymes are probably mediated by a common mechanism.
D000624:5-Aminolevulinate Synthetase / Q000096:biosynthesis*; D000438:Alcohols / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004790:Enzyme Induction / Q000187:drug effects; D000431:Ethanol / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010882:Piperonyl Butoxide / Q000494:pharmacology; D011166:Porphyrins / Q000378:metabolism
D000438:Alcohols; D011166:Porphyrins; D000431:Ethanol; D003577:Cytochrome P-450 Enzyme System; D000624:5-Aminolevulinate Synthetase; D010882:Piperonyl Butoxide