The activity of delta 5-3 beta hydroxysteroid dehydrogenase enzyme in the interrenal tissue of rainbow trout (Salmo gairdneri Richardson) exposed to sublethal concentrations of zinc.

The effects of exposure of rainbow trout (Salmo gairdneri Richardson) to three sublethal concentrations of zinc (0.248, 0.528 and 1.14 ppm) on delta 5-3 beta-hydroxysteroid dehydrogenase (delta 5-3 beta HSDH) enzyme activity in the head kidney tissue was investigated. The activity of this enzyme was localized by the reduction of a tetrazolium salt to formazan at the site of activity. Using subjective methods to indicate the degree of activity and indirectly assess the degree of corticosteroid production, the zinc-exposed rainbow trout showed a greater degree of delta 5-3 beta HSDH activity compared to the control fish. This increase in enzyme activity has been associated with the stimulation of the pituitary-interrenal axis by the noxious stress of zinc.