Danazol, a new steroidal inducer of delta-aminolevulinic acid synthetase.

Danazol (a derivative of 17 alpha-ethinyl testosterone) has recently been reported to cause clinical exacerbations of acute intermittent porphyria. In the present study, we demonstrate that danazol is an inducer of hepatic delta-aminolevulinic acid synthetase and that it increases hepatocyte porphyrin production using a chick embryo model. The findings provide an explanation for the clinical observations. Although danazol is a porphyrinogenic agent in the chick embryo and humans it has been reported to be ineffective as a porphyrinogen in rats. The present findings, therefore, also confirm the superiority of the chick embryo as a model system for the screening of drugs and chemicals which may have the potential to cause clinical exacerbations of porphyria.