Heme utilization by rat liver tryptophan pyrrolase as a screening test for exacerbation of hepatic porphyrias by drugs.

Rat liver tryptophan pyrrolase plays a versatile and unique role among hepatic hemoproteins in relation to heme utilization. The depletion of pyrrolase heme in the experimental porphyria produced by 3,5-diethoxycarbonyl-1,4-dihydrocollidine is potentiated by joint administration of any one of 19 drugs known to exacerbate the human disease, but not by any of 13 nonexacerbators. These findings form the basis of a screening test for drug exacerbation of hepatic porphyrias; the conditions, details, and requirements of which are described.