Effects of the oxidant potassium permanganate on the expression of gill metallothionein mRNA and its relationship to sublethal whole animal endpoints in channel catfish.

Potassium permanganate is an oxidant heavily used in fish culture. The effects of this compound were examined utilizing molecular (Metallothionein) and whole animal endpoints following an 8-week exposure to nominal concentrations of 0.5 (daily) and 1.0 and 2.0 mg/L (on alternate days) of potassium permanganate (PM). In order to measure MT, a complementary DNA clone of metallothionein (MT) was cloned and sequenced from the liver of channel catfish treated with a single injection of cadmium chloride (10 mg/kg). The cDNA was obtained by reverse transcriptase polymerase chain reaction (RT-PCR), using 3' rapid amplification of cDNA ends (RACE) technique. No significant correlation was observed with gill MT expression or sublethal endpoints indicative of toxicity (weight, length, condition index [CI], or liver somatic index [LSI). MT mRNA expression in gill was significantly reduced only after 8 weeks in the 2.0 mg/L treatment. Decreases in CI were observed in males at all time points after 4 weeks, at the 2.0 mg/L treatment concentration, with a NOEC of 1 mg/L. Reductions in LSI that were not dose dependent were also observed in both males and females throughout the 8-week study and no consistent reduction in weight gain or length was observed. These data demonstrate that minimal changes in sublethal effects occur in fish following 0.5-2.0 mg/L PM treatment after 4 weeks, but recovery from adverse effects is observed by 8 weeks, suggesting that acute (typically less than 1 week) treatment of channel catfish with PM would not significantly affect fish health.