Excretion of the lampricide Bayer 73 by rainbow trout

Urinary excretion of the 2-aminoethanol salt of 2′, 5-dichloro-4′-nitrosalicylanilide (Bayer 73) in rainbow trout (Salmo gairdneri) was measured after exposure of the trout to Bayer 73 and also after intraperitoneal (ip) injection of the lampricide. Fish exposed to 0.05 mg/litre of Bayer 73 for 12 h quickly began to excrete residues in the urine. The largest amount of Bayer 73 was excreted during the 12-h exposure, but the trout continued to excrete Bayer 73 beyond 60 h after exposure. After rainbow trout were given ip injections of 200 µg of Bayer 73 in corn oil, they excreted up to 25 percent of the injected dose in the urine, and 20 percent was recovered in the bile at the end of the study. In both groups of fish most of the renal excretion of Bayer 73 was as the glucuronide conjugate. The exposure of rainbow trout to Bayer 73 at the doses studied had no effect on the urine output or on the renal excretion of sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), and chloride (Cl^-).