Accumulation of nitrate in the tissues of Penaeus monodon following elevated ambient nitrate exposure after different time periods.

Penaeus monodon (10.56 +/- 0.71 g) exposed individually to 0.026 (control), 0.774, 3.646, 7.004, 21.234 and 36.079 mM nitrate in 25 ppt seawater were examined for nitrate accumulation in hemolymph, gill, eyestalk, heart, foregut, midgut, hepatopancreas and muscle after 1, 3, 6, 12 and 24 h, respectively. Concentration of nitrate in the tissues increased directly with ambient nitrate concentration and exposure time except for muscle. Following 24-h exposure to 3.646 mM nitrate, nitrate concentrations measured in the muscle (0.202 micromol g(-1)), hepatopancreas (0.330 micromol g(-1)), heart (0.527 micromol g(-1)), foregut (0.632 micromol g(-1)), gill (0.927 micromol g(-1)), hemolymph (0.946 micromol ml(-1)), eyestalk (1.214 micromol g(-1)), and midgut (1.529 micromol g(-1)), respectively. The concentration of muscle nitrate was the lowest, and the concentration of midgut nitrate was the highest among the tissues tested. P. monodon following exposure to ambient nitrate at 21.234 and 36.079 mM, nitrate accumulation measured in the muscle (0.854 and 0.980 micromol g(-1)), hepatopancreas (1.139 and 1.552 micromol g(-1)), heart (1.468 and 1.879 micromol g(-1)), foregut (2.195 and 3.341 micromol g(-1)), gill (2.398 and 3.325 micromol g(-1)), hemolymph (3.327 and 3.948 micromol ml(-1)), eyestalk (3.461 and 4.264 micromol g(-1)) and midgut (3.343 and 5.239 micromol g(-1)), and never reached a plateau after 24 h.