Comparative effects of antimycin a on isolated mitochondria of channel catfish ( Ictalurus punctatus) and rainbow trout ( salmo gairdneri)

1. At 18°C, the average control respiration rate of trout liver mitochondria was higher than that of channel catfish. 2. The liver mitochondria of channel catfish and trout respond in a similar manner to antimycin concentrations from 10 to 100 ppb. 3. Antimycin concentrations from 300 ppb to 1 ppm, caused a greater % inhibition to the respiration of trout mitochondria (80–96%) than to catfish mitochondria (42–67%). 4. At antimycin concentrations from 300 ppb to 1 ppm, trout had control respiration rates almost double those of catfish and treatment rates lower than those of catfish. 5. These results suggest that the tolerance of catfish to antimycin is located at the mitochondrial level and is possibly related to a difference in the electron transport system.