Effects of age, phenobarbital, β-naphthoflavone and dexamethasone on rat hepatic δ-aminolevulinic acid synthase

δ-Aminolevulinic acid synthase is a key enzyme leading to the synthesis of cytochrome P-450, a compound of the mixed function oxidase system. Because of this, we have studied the effects of both age and three typical mixed function oxidase system induces on this enzyme activity in male Wistar rats. Our results suggest that δ-aninolevulinic acid synthase activity in intact rats increases up to maturity and then decreases being, however, higher in the oldest animals than in the youngest. Phenobarbital affects δ-aminolevulinic acid synthase activity very characteristically. This activity is high in 4-week-old animals and then increases slightly until the twelfth month of life. Phenobarbital enzymic inducibility tends to decrease with age. In the β-naphthoflavone groups, the profile of δ-aminolevulinic acid synthase activity looks like that in the control ones. Generally, β-naphthoflavone is a weaker δ-aminolevulinic acid synthase inducer than phenobarbital, but it seems to induce δ-aminolevulinic acid synthase like dexamethasone, which, being a physiological inducer of the mixed function oxidase system, is also an inducer of δ-aminolevulinic acid synthase and this inducibility is closely connected with age.