CATALYTIC CONVERSION OF L-ARGININE TO NITRATE BY PLATINUM-ELECTRODES

Platinum electrodes (PLE) have been used recently to study the physiol ogic effects of the enzymatic conversion of L-arginine (L-arg) to nitr ic oxide (NO) by nitric oxide synthase (NOS). We sought to determine i f PLE alone could catalytically convert L-arg to NO without NOS. Accor dingly, NO2- + NO3- levels (NOx) were measured by HPLC from a physiolo gic Tyrode's buffer in the presence and absence of electrical stimulat ion with PLE or silver chloride electrodes (SCE) for 10 min (n=6 for e ach condition). PLE stimulated at 1Hz produced 24+/-0.7 and 15.4+/-2.8 mu M NOx from D-arg and L-arg (100mM) respectively. PLE+L-arg stimula ted from 0 to 5 Hz produced increasing NOx +/-0.27;15.4+/-2.8;19.7+/-4 ;32+/-5;37+/-6.2;43+/-7 mu M). SCE+L-arg showed no increase in NOx abo ve background. The addition of 1% BSA to the Tyrode's buffer further i ncreased NOx levels. NO2- levels were undetectable, indicating all NOx levels were NO3-. We conclude that PLE can catalytically convert L-Ar g to NO3- via electron transfer without NOS. (C) 1994 Academic Press, Inc.