Delta-aminolevulinic acid dehydratase (ALAD) is an enzyme involved in the biosynthesis of heme, in which it catalyzes the condensation of two molecules of delta-aminolevulinic acid to one molecule of porphobilinogen. It is a sulfhydryl enzyme, which means, among other things, that its activity is inhibited by many heavy metals. In the present investigation rabbits were given either zinc or lead or both. Zinc had a strong activating effect on ALAD in vivo, and the inhibitory effect of lead was almost completely eliminated. A close positive correlation was found between ALAD in the red blood cells and zinc in the plasma, but there was no correlation between ALAD and zinc in the red blood cells. These observations are of particular interest in the light of recent findings, suggesting that zinc is an essential metal for ALAD.

Animals↗

PubMedDate not supplied

Antagonistic effects of zinc and aluminum on lead inhibition of delta-aminolevulinic acid dehydratase.

In vitro and in vivo studies regarding the influence of metals on delta-aminolevulinic acid dehydratase activity in erythrocytes indicate that a lead concentration of 4 micrometer/l completely inhibits the enzyme. Zinc activates the enzyme both in vitro and in vivo at concentrations greater than 76 micrometer/l. Aluminum has an inhibitory effect at all concentrations in vitro whereas it activates the enzyme in vivo. Zinc and aluminum together activate the enzyme in vivo. The in vitro activation of zinc is inhibited by increasing concentrations of aluminum. Aluminum and lead together depress the enzyme activity in an additive way that can be reactivated by the addition of zinc.

Aluminum↗

PubMedDate not supplied

Oral carotenoids for photohypersensitivity in patients with erythrohepatic protoporphyria, polymorphous light eruptions and lupus erythematodes discoides.

beta-Carotene and canthaxanthin in a dose of 75--250 mg a day by mouth reduced the symptons of exposure to the sun in all 7 treated patients with erythrohepatic protoporphyria (EPP), in 15 of 18 with polymorphous light eruptions (PMLE) and in 3 of 4 with lupus erythematodes discoides. In the EPP group the protoporphyrin level tended to vary inversely with that of the serum carotenoids. The level of retinol-binding protein in plasma remained unchanged despite a substantial rise in the concentration of the serum carotenoids. Estimation of the minimal erythema dose for unfiltered light from a Xenon lamp in 7 patients with PMLE showed an increase in only 1 patient. Neither clinical examination nor repeated laboratory studies revealed any serious side effects of the treatment.

Administration, Oral↗