Comparative Goitrogenic Activity of Tapazole and Carbimazole in Cattle

Abstract

The comparative goitrogenicity of two compounds, tapazole (1-methyl, 2-mercaptoimidazole) and carbimazole (1-methyl, 2-thio, 3-carbethoxyi-midazole) was determined in cattle by I¹³¹ uptake suppression and by I¹³¹ release measurements. By the former measurement carbimazole and tapazole were found equipotent and 3 gm./1000 lb. body weight completely blocked thyroxine secretion. By I¹³¹ release rate measurements, however, carbimazole was about twice as potent as tapazole in blocking thyroxine synthesis. The implications of the differences in the potency of the goitrogens by different techniques are discussed. Copyright © . .