Elevated serum cortisol and glucose and liver glycogen in juvenile fish Clarias lazera after exposure to acid stress.

The exposure of juvenile Clarias lazera to acute (pH 3.1 for 96 h) and chronic (pH 5.4 or 4.7 for 12 weeks) acid stress (H2SO4) resulted in a number of physiological responses which could be considered as adaptive to the effects of stress. These responses were evident in the rapid rise of serum cortisol level from 43.0 +/- 0.76 microgram/dl in the control to 71.0 +/- 1.06 micrograms/dl (P < 0.001) 24 h after acute exposure. Also serum glucose level was increased from 123.66 +/- 1.85 mg/dl in the control and reached 295.0 +/- 2.89 mg/dl (P < 0.001) by the end of the experimental period (96 h). Chronic exposure of the fish to the two levels of pH (5.4 and 4.7) caused significant increase in serum cortisol and serum glucose level starting from the first week of exposure and lasted throughout the study period (12 weeks). As to the liver glycogen content, a slight but significant drop was found from 11.06 +/- 0.03 mg/100 mg tissue dry weight in the control to 10.80 +/- 0.06 mg/100 mg tissue dry weight (P < 0.025) 24 h after acute acid exposure. However, the values at 72 and 96 h were significantly higher than those in the control. In the chronic exposure study, the fish maintained at pH 5.4 showed a marked increase in liver glycogen content starting from week 2 and lasted till the end of experimental period (12 weeks). As early as after one week of treatment, in fish maintained in pH 4.7, liver glycogen content surged and remained significantly high till the twelfth week.