Fate of porphobilinogen, administered enterally or parenterally, in the rat

Publisher Website
Google Scholar
Abstract
Porphobilinogen was administered parenterally and enterally to rats. After parenteral injection, porphobilinogen was rapidly and mainly excreted in the urine. Small amounts were excreted in the feces. After enteral administration, only small amounts were slowly excreted in the urine. Most of it was passed unchanged in the feces. The porphobilinogen excreted in urine was identical chromatographically with that administered. A calculation of renal clearance of porphobilinogen in the rat suggests that por-phobilinogen is mainly excreted by glomerular filtration without significant reabsorption. A small but significant rise of co-proporphyrin HI, as well as the excretion of some uroporphyrin III, was noted in rat urine after parenteral injection of por-phobilinogen. There was no significant change in fecal porphyrin excretion after enteral or parenteral administration of por-phobilinogen. Aerobic incubation in vitro at 37[degree] of porphobilinogen with gastro-intestinal contents of a rat showed no evidence of conversion of porphobilinogen into porphyrins. Porphobilinogen was not found in the liver when rats were killed shortly after its enteral or parenteral administration, nor was it found in the liver of a rat after subcutaneous injections of porphobilinogen every half-hour for 20 hours, during which time a high plasma porphobilinogen concentration was maintained. These findings suggest that the prophobilinogen found in the liver of a rat with experimental porphyria is in fact formed there and is not trans-ported by the blood stream to the liver from an extrahepatic site. The relevance of these results, obtained in the rat, to human acute porphyria, is discussed.
Keywords