Renal Mechanism for Excretion of Porphyrin Precursors in Patients with Acute Intermittent Porphyria and Chronic Lead Poisoning.

A RAPID and accurate diagnosis of acute intermittent porp11yri t ( AlP) became possible once suitable methods were available for measurement of urine content of -aminolevulinic acid ( AI A ) and porphobilinogen (PBG).”2 Similarly, in lead poisoning, determination of ALA excretion has proven a useful chemical adjunct, both for diagnostic and therapeutic evaluation.3 The biochemical defect( s ) which result in increased excretion of porphyrin precursors in these two diseases remain unknown. At present, evidence favors overproduction of ALA and PBG in acute porphyria,4 and decreased utilization of ALA in bead intoxication.5 However, despite the direct role of the kidney, which provides the final excretory pathway for these metabolites, investigations of the renal mechanism for ALA and PBG excretion are sparse. Both ALA and PBG are amino acids. Of pertinence are the reports of a generalized aminoaciduria occurring during experiniental porphyria,#{176} cliiiical AlP,7 experimental bead intoxication,5 and clinical lead poisoningY In each instance, an aminoaciduria has been documented in association with an abnormally increased excretion of ALA. The possibility that renal al)nOrmalities may contribute to increased ALA exc’retion in lead poisoning has been considered, #{176} but has not been investigated. In this communication, we report studies of renal excretion of ALA and PBG based on measurements of their endogenous clearance. Subject material includes women with AlP, men with chronic lead poisoning, and normal controls. In addition, amino acid excretion among patients with AlP has been examined. A single report demonstrated general aniinoaciduria in 12 patients;7 we have attempted to confirm and extend this observation.