DOWN-REGULATION OF PISCINE FLAVIN-CONTAINING MONOOXYGENASE ACTIVITY BY DECREASED SALINITY IN EURYHALINE FLOUNDER (PLATICHTHYS-FLESUS)

Flavin-containing mono-oxygenases (FMOs) play a significant role in xe nobiotic biotransformation in fish. However, endogenous functions of t he enzyme have not been documented. Earlier studies in our laboratory indicated a relationship between FMO expression and osmoregulation in euryhaline fish. Consequently, in the present study, euryhaline flound er (Platichthys flesus) were exposed to three separate salinity regime s fr two weeks. Hepatic and branchial FMO activity was examined in ind ividual animals from each exposure and was found to be directly relate d to the salinity in which the fish were kept. Thus, an association be tween osmoregulatory function and FMO expression was observed in euryh aline fish indicating possible divergent or simultaneous evolution of the enzyme system to a xenobiotic metabolizing function. Copyright (C) 1996 Elsevier Science Ltd