The Absorption and Distribution of 14C-Bacitracin in Rainbow Trout (Salmo gairdneri) after a Single Oral Dose, as Observed by Whole Body Autoradiography

: This study was performed to investigate the absorption, distribution and elimination of orally given radiolabelled bacitracin methylene disalicylate (BMD) in rainbow trout kept in salt water. The level of radioactivity in skeletal muscle tissue remained low, but stable throughout the experiment, while radioactivity in bile and liver tissue increased for about 48 hr, before decreasing. There was a trapping of BMD and/or its metabolites in excretory kidney tissue, where the amount of radioactivity continued to increase when radioactive material was being removed from other tissues. The maximum concentration found in excretory kidney tissue was about 7 times as high as the maximum concentration found in the liver. Even though there is no appreciable absorption of BMD from the gastrointestinal tract in homoiotherms, we found the absorption in rainbow trout to be significant.