Background: Porphyria cutanea tarda and haemochromatosis are taken to be spontaneous human models of oxidative cellular damage, with an increased risk of fibrosis and cancer evolution.

Aim: To define the relative pro-oxidant roles of porphyrin and iron, in their different molecular forms, and their effects on antioxidant biological systems.

Patients: A group of 17 patients with porphyria cutanea tarda and a group of 14 patients with primary and secondary haemochromatosis, were compared with 21 healthy controls.

Methods: Plasma retinol, tocopherol, alpha- and beta-carotene, ascorbic acid, glutathione, malonyldialdehyde and red blood cell free iron were determined using high performance liquid chromatography.

Results: Only a modest increase in iron stores was demonstrated in the porphyria cutanea tarda group; in the haemochromatosis patients ferritin levels were almost seven times higher. By contrast, there was a sharp and virtually identical increase in red blood cell free iron and malonyldialdehyde in both the patient groups. A significant reduction was observed in retinol, alpha-, beta-carotene and red blood cell glutathione levels being more marked in porphyria cutanea tarda than in haemochromatosis patients.

Conclusions: The study confirms the strong pro-oxidant effects of porphyrins in vivo, through an induction of the free toxic iron form, even though the total iron pool is not greatly expanded. The additional free-iron and porphyrin oxidant effects are documented both in red blood cell and plasma in the porphyria cutanea tarda group. It confirmed that aging exerts a negative influence in terms of pro- and antioxidant balance in all cases, but particularly in the haemochromatosis group.