IS S-NITROSO-N-ACETYL-L-CYSTEINE A CIRCULATING OR AN EXCRETORY METABOLITE OF NITRIC-OXIDE (NO) IN MAN - ASSESSMENT BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

S-Nitroso-L-cysteine has been shown to be a circulating metabolite of the L-arginine-derived nitric oxide (NO) in mammals. We describe here a highly sensitive gas chromatographic-mass spectrometric (GC-MS) meth od for the measurement of S-nitroso-N-acetyl-L-cysteine, the potential mercapturic acid of S-nitroso-L-cysteine, in human plasma and urine. For use as internal standard (LS.) in this method we synthesized S-[N- 15]nitroso-N-[H-2(3)]acetyl-L-cysteine. In plasma (n = 10) and urine ( n = 30) samples of healthy humans no S-nitroso-N-acetyl-L-cysteine was detected (detection limit approximate to 1 nM). Injecting the I.S. in the rat showed a good recovery of the I.S. but no endogenous S-nitros o-N-acetyl-L-cysteine. Our results suggest that renal N-acetylation of S-nitroso-L-cysteine does not represent a metabolic pathway in man. ( C) 1996 Academic Press, Inc.