Porphyrinostatic effect of isonicotinic acid hydrazide on porphyric chick embryo and yeast.

1. The common feature of "inducible" forms of hepatic porphyria is an increased activity of delta-amino-levulinate/ALA/synthase. 2. As a potential therapeutic procedure, isonicotinic acid hydrazide/INH/as inhibitor of this enzyme, was applied and found to show a porphyrinostatic effect, depending on its concentration, both in yeast and porphyric chick embryo models. 3. Moreover, pyridoxalphosphate/PDX/eliminated the porphyrinostatic effect of INH, depending again on its concentration. 4. Histochemical tests did not demonstrate any significant functional or morphological changes in the chick embryo hepatocytes following INH administration.