CYANIDE EXPOSURE AFFECTS THE PRODUCTION AND EXCRETION OF AMMONIA BY THE MUDSKIPPER BOLEOPHTHALMUS-BODDAERTI

The concentrations of ammonia in the plasma of the mudskipper Boleopht halmus boddaerti exposed to Cyanide for 1-6 days were significantly gr eater than the respective values of the controls. This was due to an i ncrease in the production of NH3 in the muscle and an increase in the retention of NH3 and/or NH4+ in the blood of the cyanide-exposed fish when compared to controls. Cyanide exposure significantly increased th e specific activity of muscle AMP deaminase. Since adenylosuccinate sy nthetase and lyase were also present in the muscle, exposure to cyanid e might increase the production of NH3 from the catabolism of purine n ucleotides. B. boddaerti exposed to cyanide excreted significantly les s ammonia than the control fish. Results indicate changes in the perme ability of the epithelial surfaces of the cyanide-exposed fish to NH3 and/or NH4+. Since the tissues and organs needed time to activate the inducible cyanide detoxification mechanisms, the increase in the produ ction of NH3 might be an important defensive mechanism for B. boddaert i during the early phase of cyanide exposure. (C) 1998 Elsevier Scienc e Inc. All rights reserved.