Biochemical and stress-attenuating effects of butaphosphan-cyanocobalamin combination drug in olive flounder Paralichthys olivaceus

Abstract

Butaphosphan {[1-(butylamino)-1-methylethyl]-phosphonic acid (BTP)}-cyanocobalamin [vitamin B12 (C)], a combination drug comprising an organic source of phosphorus and a synthetic form of vitamin B12, is used to attenuate stress responses in livestock. This study was performed to examine the effects of BTP-C in olive flounder Paralichthys olivaceus under normal and stressful conditions. P. olivaceus was intramuscularly injected with BTP-C (50–300 mg BTP-C/kg body weight) under normal conditions and changes in muscle adenosine nucleotides examined. BTP-C increased adenosine 5′-triphosphate (ATP) levels; this effect was more pronounced at 22 °C than at 13 °C. Serum transaminase levels were also elevated at a dose of 300 mg BTP-C/kg, which suggested possible hepatotoxicity of the drug. Effects of BTP-C on stress were examined by injecting it at a rate of 50 mg/kg. BTP-C partially prevented hypothermia- and hypoxia-induced reduction in feeding. Serum immunoglobulin M levels were increased by BTP-C in these stress tests. Although BTP-C did not affect hypothermia-induced cortisol elevation or lysozyme reduction, changes in these parameters due to hypoxia were alleviated by the drug. Stress-attenuating effects of BTP-C were also confirmed in fish farms following injection of an antibiotic. These results indicate that BTP-C may be useful against various forms of stress in fish. Accelerated ATP production following the administration of BTP-C is one possible mechanism resulting in the attenuation of stress effects. The clinically effective dose of BTP-C, 50 mg/kg, did not cause any marked toxicity in P. olivaceus.