Concentrations of Various Sulfonamides in the Tissues of Rainbow Trout after Oral Dosage

Five kinds of sulfonamides, sulfamerazine, sulfisomidine, sulfisoxazole, sulfadimethoxine and Sulfamonomethoxine were given orally to the rainbow trout, and the concentrations in the tissues were then studied. The experiments were made on the rainbow trout yearling of its average body weight being from 75 to 80gr.. The individual fish was given one of the above sulfonamides 250mg. per one killogram of the body weight in a single dose, and therafter the concentrations of sulfonamides in plasma, liver, muscle and kidney of the fish were determined by the Bratton and Marshall modification method. The water temperature in the rearing tanks varied between 7.2 and 15.0°C. The results were all summarized in Tables 1 to 5, and Figs. 1 to 3, showing that the absorption of sulfonamides into the fish tissues, when compared with the one in mammals, was taken place neither quickly nor fully, while the sulfonamides maintained their effective level in the tissues for a long time. Out of the sulfonamides tested sulfomonomethoxine and and Sulfamerazine were well absorbed, and they continued to be effective a good while. Sulfisomidine and Sulfisoxazole, on the other hand, were soon excreted after a temporary abiding in the tissues. Nearly no absorption was observed in the case of Sulfadimethoxine. As for the concentration level of the sulfonamides in the tissues, except for sulfamerazine, the highest value was seen in liver, corresponding about double the one in plasma and kidney, while the muscle level was as low as half the plasma level.