Suppression of neutrophil migration and chemiluminescence is due to the sulphur atom in the thiobarbiturate molecule.

In this study the hypothesis was tested that the substituent at the C 2 position of the barbiturate molecule is crucial for the obvious differences in inhibitory potencies between various barbiturates with respect to neutrophil functions in vitro. Using isolated neutrophils from healthy volunteers, the comparative effects of two pairs of sulphur or oxygen-substituted analogues on chemiluminescence, random and chemotactic migration were examined. Five other i.v. barbiturates were also tested in the chemiluminescence assay. The key observation with all the assay systems was that the oxybarbiturates proved ten to a hundredfold less suppressive than their sulphurated analogues or the other thiobarbiturates. Thus, enhanced inhibitory potency was dependent on the presence of the sulphur atom in the barbiturate molecule and could no longer be explained exclusively on the basis of divergent physicochemical features.