Nys. Woo et Sf. Chiu, METABOLIC AND OSMOREGULATORY RESPONSES OF THE SEA BASS LATES-CALCARIFER TO NITRITE EXPOSURE, Environmental toxicology and water quality, 12(3), 1997, pp. 257-264
Sea bass (Lates calcarifer) were exposed to seawater containing 0, 30,
50, or 80 mg L-1 NO2-N for 4 days, and changes in metabolite levels a
nd enzyme activities were assessed. Distinct signs of osmoregulatory d
ysfunction were evident in nitrite-exposed fish as serum Na+ and Cl- l
evels were elevated and branchial Na+-K+-ATPase activity was significa
ntly reduced. Serum lactate and protein levels were significantly elev
ated and lowered respectively only at the highest nitrite level (80 mg
L-1 NO2-N). Significantly increased serum ammonia and urea and decrea
sed serum glucose and liver glycogen levels were evident also at lower
nitrite levels. Liver water, liver protein and lactate, brain and mus
cle lactate, and muscle water content were unaffected. In the liver, s
ignificant decreases were observed for the activities of glycogen phos
phorylase a, glutamate-oxaloacetate transaminase, and glutamate dehydr
ogenase, but the activities of lactate dehydrogenase, isocitrate dehyd
rogenase, glucose-6-phosphatase, glutamate-pyruvate transaminase, and
glucose-6-phosphate dehydrogenase were unaffected. While ATP, ADP, and
AMP levels were all lowered in nitrite-exposed fish, the adenylate en
ergy charge was maintained at fairly constant level. By producing ammo
nia via the degradation of AMP to IMP, stabilization of the adenylate
energy charge can be achieved. It is postulated that this event probab
ly represents an adaptive strategy employed by the sea bass to counter
act nitrite toxicity. (C) 1997 by John Wiley & Sons, Inc.