Hepatic Porphyria and the Synthesis of ALA

Approximately 210 mg of heme are formed daily in the bone marrow of the adult to replace the hemoglobin lost through red cell breakdown. Since eight molecules of ALA are required to form one molecule of heme, about 358 mg of ALA are required for this amount of heme synthesis. In the inherited disease AIP, the liver may readily produce this much or more ALA yet normally the liver makes only about 15% of the ALA that is made by the bone marrow. It is obvious, therefore, that in the liver there is an important control mechanism for ALA synthesis revealed by this disease. Depending on the type of hepatic porphyria, the ALA which is produced may be excreted together with porphobilinogen in the urine, or it may excreted in the form of porphyrins in the urine and feces [2,4,6,11]. 

A number of the symptoms of acute intermittent porphyria have provided clues toward a more basic understanding of this disease which are discussed more fully in a later section. For example, the excretion 

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