The results of change of the activity of enzymes of synthesis (aminolevulinate synthase, aminolevulinic acid dehydratase and hemesyntethase) and decomposition (hemeoxydase) of heme in the liver of rats due to the experimentally disturbed porphyrin metabolism have been presented. The increase in the activity of enzymes of ALA-synthase and ALA-dehydratase has been found, and it led to accumulation of free porphyrins in the liver. At the same time the increase in activity of heme oxygenase has been also revealed. The reduced heme synthesis correlated with decreased levels of cytochrome P450 and b5 in the microsomal fraction of the liver in experimental animals. The course of all these changes reflects the state of the heme metabolism in the conditions of the experimentally disturbed porphyrin metabolism, which is characterized by the initial activation of enzymes of synthesis and a gradual decrease in their activity on the background of intensification of the heme metabolism.
Key words: heme, aminolevulinate synthase, hemesyntethase, hemeoxydase porphyrins