Porphyrin metabolism in rats intaking chemical carcinogens A.F. Abdel-Aziz*, M.M.H. El-Sharabasy, M.A. El-Far, Wafaa M. Yousef Biochemistry Division, Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Egypt Received 17 March 1997; received in revised form 9 April 1998; accepted 9 April 1998 Abstract 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 d-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.  1998 Elsevier Science Ireland Ltd. All rights reserved Keywords: Porphyrin metabolism; Chemical carcinogens 1. Introduction Disturbances of haem synthesis, and thereby por- phyrin metabolism, are well-known in patients with chronic liver diseases of various aetiology, such as heavy metal exposure, liver cirrhosis and chronic hepatitis [5]. Also, such disturbances have been reported in bone marrow diseases such as leukaemia, prenicous and haemolytic anaemias [2,9]. A number of case reports have been published on patients with benign as well as malignant liver tumours, including liver metastasis, coincident with symptomatic hepatic porphyria clini- cally manifested as porphyria cutanea tarda [32,33]. An increased risk of hepatocellular cancer has been reported in patients with porphyria cutanea tarda [26]. Indeed, the relationship between haem metabolism and carcinogenesis deserves more attention than it has received [20,31]. Some carcinogenic processes may disturb haem biosynthesis [5,36] to such an extent that porphyric tumours occur in surrounding porphy- ric tissues [21]. Moreover, successful treatment of different neoplasia with chemical derivatives of por- phyrins and visible light [29] has stimulated this research to study porphyrin metabolism during the intake of a potent liver carcinogen for use as diagnos- tic and therapeutic tools for liver metastasis. 2. Materials and methods This study was carried out on male rats with an Cancer Letters 130 (1998) 77–81 0304-3835/98/$19.00  1998 Elsevier Science Ireland Ltd. All rights reserved PII S0304-3835(98)00117-7 * Corresponding author.