Effect of Histamine and an Anti-Histammic Drug on the Hæmolytic Action of Guinea Pig Complement

Abstract

Cushman, Becker and Wirtz¹ have shown that the antihistaminic drug theophorin is a potent inhibitor of the hæmolytic action of complement. It is therefore of interest to study the effect of another antihistaminic drug and of histamine. Thenfadil (N : N-dimethyl-N′-2-pyridyl-N′-(3-thenyl)-ethylene-diamine) was chosen for study². In a preliminary experiment 0.012 M thenfadil inhibited hæmolysis by 56 per cent, while 0.010 M histamine inhibited it by 44 per cent. Inhibition in the presence of both compounds at these concentrations was 94 per cent. This suggested that both histamine and thenfadil can inhibit hæmolysis in a similar way. This inhibition was not due to increased concentration of salt³, which, under the conditions of these experiments, had very much smaller effects. Further experiments were undertaken to determine the mechanism of inhibition by histamine and thenfadil, and thioglycollate, a known C′-inhibitor¹, was also tested. (Complement and its four components are designated C′, C′1, C′2, C′3, C′4, respectively.)