Thiourea and dimethylthiourea inhibit peroxynitrite-dependent damage: Nonspecificity as hydroxyl radical scavengers

and, more recently, dimethylthiourea, have been used as hydroxyl radical (OH.) scavengers in experiments both in vitro and in vivo. We show that both compounds can inhibit nitration of the amino acid tyrosine on addition of peroxynitrite, and also the inactivation of alpha(1)-antiproteinase by peroxynitrite. Hence, protective effects of (dimethyl) thiourea could be due to inhibition of peroxynitrite-dependent damage as well as to OH. scavenging, and these compounds must not be regarded as specific OH. scavengers. (C) 1997 Elsevier Science Inc.