Sampling and storage conditions of rainbow trout liver affects monooxygenase and conjugation enzymes.

1. The effect of storage conditions of rainbow trout (Salmo gairdneri) liver on monooxygenase and conjugation enzyme activities was studied. Fish livers or whole fish were frozen and stored for various periods of time at -4, -20 or -80 degrees C. 2. Freezing the whole fish at -20 degrees C affected the biotransformation enzyme activities dramatically. The loss of monooxygenase activity exceeded up to one-tenth of the initial rate in 17 days. UDP-Glucuronosyltransferase activity increased 50%. Glutathione S-transferase appeared to be the most durable enzyme. 3. When the whole fish were stored in an ice-bath at -4 degrees C for up to 24 hr the activities measured decreased only half of that when frozen for 3 days. 4. When it is impossible to freeze the tissues studied in liquid nitrogen the activities are best preserved when whole, decapitated, bled fish are kept in an ice-bath for less than 24 hr.