Studies on porphyrin biosynthesis in lead-intoxicated rabbits

Porphyrin metabolism in some malignant diseases

Porphyrin metabolism was studied in 21 children of both sexes suffering from acute lymphoblastic leukaemia (ALL) and 34 adult patients of different ages and sexes suffering from ALL (n = 14), non-Hodgkin's lymphoma (NHL), n = 14, or Hodgkin's disease (HD), n = 6. In addition, two groups of healthy children (n = 14), and adults (n = 17) were studied for comparison. It was apparent from this study that the activity of uroporphyrinogen-1-synthetase (URO-1-S, E.C. 4.3.1.8) was highly significantly activated in the blood of children, while the activities of blood 5-aminolevulinic acid dehydrase (E.C. 4.2.1.24) and ferrochelatase (E.C. 4.99.1.1.), as expressed by protoporphyrin/haem ratio, were inhibited in those children. Also, free erythrocyte total porphyrins were increased, while the haem content was reduced. The concentrations of 5-aminolevulinic acid, coproporphyprin and uroporphyrin were increased in the urine of children with ALL. On the other hand, some dramatic changes were found in porphyrin metabolism in adult patients suffering from ALL, NHL and HD. The aforementioned disturbances were discussed in the light of some factors which may affect the enzymatic activities in the synthesis of porphyrins.

Erythrocyte porphyrinogen carboxy-lyase activity in porphyria cutanea tarda and certain other human porphyrias

Red cell porphyrinogen carboxy-lyase activity was measured using uroporphyrinogen III as substrate in 18 normal persons, 7 male patients with porphyria cutanea tarda, 3 female patients with erythropoietic protoporphyria and 2 female patients with variegate porphyria. The mean values obtained in normal subjects were 0.151 nmol of uroporphyrinogen disappeared in 30 min per mg of protein, and 0.038 nmol of coproporphyrinogen formed in 30 min per mg of protein. We have not been able to detect significant differences between males and females. In porphyria cutanea tarda the enzyme activity was the same as in normal subjects considering either substrate disappearance or end product formation. The differences were not significant at the p less than 0.05 level. Patients with variegata porphyria also exhibited normal erythrocyte porphyrinogen carboxy-lyase activity. The enzyme activity of erythrocytes from patients with erythropoietic protoporphyria was higher than in normals; mean values for specific activities being 0.204 nmol of uroporphyrinogen disappeared, and 0.071 nmol of coproporphyrinogen formed. The significance of the results with respect to the chemical picture of different porphyrias is discussed.