Porphyrin metabolism in rats intaking chemical carcinogens

This study was performed on rats receiving nitrosamine precursors as potent liver carcinogens in order to investigate and follow up the porphyrin metabolism during the intake of hepatocarcinogens. As clarified from our results, progressive increases in free erythrocyte porphyrins, erythrocyte protoporphyrins, haem content and hepatic total porphyrins were observed after 2 months of intaking these carcinogens and further increases were gradually observed in parallel with the continued intake of these chemicals, which was extended to 7 months. At the same time, such elevations were also observed in the activity of hepatic δ-aminolevulinic acid (ALA)-synthetase and uroporphyrinogen-1-synthetase either in hepatic tissues or erythrocytes of these carcinogen-subjected rats. However, significant inhibition was found in the activity of erythrocyte ALA-dehydratase, which reached 40.5% of the control values after 7 months. Therefore, these observations demonstrated that the intake of hepatocarcinogens may influence the rate of hepatic porphyrin and haem biosynthesis.