title: Depletion of liver regulatory heme in benzene exposed rats.
abstract: The effect of a single dose of benzene (0.5 ml/kg body wt i.p.) on the heme saturation of tryptophan pyrrolase activity in liver was examined. There was a significant decrease in the heme saturation of hepatic tryptophan pyrrolase, suggesting depletion of "regulatory heme". After benzene administration there was significant increase in delta-aminolevulinate (ALA) synthetase activity (approx. 2-fold) while delta-aminolevulinate dehydratase activity was significantly decreased, however, ferrochelatase and heme oxygenase activities were unaltered. Administration of tryptophan to benzene pretreated rats showed a reversal of benzene effects on heme synthesizing enzymes: there is an increase in the heme saturation of tryptophan pyrrolase and decrease in delta-aminolevulinate synthetase. However, there was no significant alteration in the activity of delta-aminolevulinate dehydratase.
authors.affiliation: Industrial Toxicology Research Centre, Lucknow, India.
authors.forename: S M
authors.initials: SM
authors.lastname: Siddiqui
authors.forename: G S
authors.initials: GS
authors.lastname: Rao
authors.forename: K P
authors.initials: KP
authors.lastname: Pandya
mesh_terms: D000624:5-Aminolevulinate Synthetase / Q000032:analysis; D000818:Animals; D001554:Benzene / Q000633:toxicity*; D005260:Female; D006418:Heme / Q000378:metabolism*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D000623:Porphobilinogen Synthase / Q000032:analysis; D051381:Rats; D014364:Tryptophan / Q000494:pharmacology; D014366:Tryptophan Oxygenase / Q000032:analysis
chemical_list: D006418:Heme; D014364:Tryptophan; D014366:Tryptophan Oxygenase; D000624:5-Aminolevulinate Synthetase; D000623:Porphobilinogen Synthase; D001554:Benzene