title: The effect of exogenous  -aminolaevulinate on rat liver haem and cytochromes.
abstract: The activity of delta-aminolaevulinate synthetase is generally regarded as rate-limiting for hepatic haem biosynthesis. It has been suggested that cytochrome synthesis may also be regulated by changes in delta-aminolaevulinate synthetase activity. This hypothesis was studied by injecting product, delta-aminolaevulinate, into adult rats over a 4-240h period. The concentrations of hepatic mitochondrial cytochromes a, b, c and c(1) were unchanged by treatment with delta-aminolaevulinate, allylisopropylacetamide or phenobarbital. In control animals, total microsomal haem content equalled the sum of cytochromes b(5) plus P-450. After delta-aminolaevulinate administration the total amount of microsomal haem, measured as the pyridine haemochromogen, exceeded these components, indicating the formation of a ;free' haem pool. Haem synthesis does not appear rate-limiting for hepatic cytochrome synthesis in the adult rat.
mesh_terms: D000624:5-Aminolevulinate Synthetase / Q000378:metabolism*; D000577:Amides / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D002247:Carbon Isotopes; D003580:Cytochromes / Q000032:analysis / Q000096:biosynthesis*; D006418:Heme / Q000096:biosynthesis*; D007982:Levulinic Acids / Q000008:administration & dosage / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000032:analysis; D008930:Mitochondria, Liver / Q000032:analysis; D010634:Phenobarbital / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D013053:Spectrophotometry; D014366:Tryptophan Oxygenase / Q000032:analysis
chemical_list: D000577:Amides; D002247:Carbon Isotopes; D003580:Cytochromes; D007982:Levulinic Acids; D006418:Heme; D014366:Tryptophan Oxygenase; D000624:5-Aminolevulinate Synthetase; D010634:Phenobarbital