Concerning the Metabolism of D - and L - a , y - Diaminobutyric Acid - 2 - C 14 in Rats *

The L isomer of (Y , y-diaminobutyric acid is a major component of the polymixin group of antibiotics (1) and of certain Lathyrus peas (24). Some of the polymixins alsocontain~-a:,y-diaminobutyric acid (1). Although the L acid appears to be neurotoxic in rats, it may not be the neurotoxic agent of human lathyrism (4). Except for distribution and toxicity studies in mice (5, 6) and uptake studies with ascites tumor cells (5, 7, 8), investigations concerning the mammalian metabolism of these diaminobutyric acids have not been reported. We have prepared Dand L-(Y) y-diaminobutyric acid-2-V and have studied their metabolism in rats. Considerable radioactivity from each isomer was excreted in the urine. The L isomer was more readily converted to respiratory 040% A major urinary catabolite of each isomer was shown to be P-alanine-l-C14.