Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2005
Publication Date: 2/8/2006
Citation: Davis Jr., K.B., Small, B.C. 2006. Rates of cortisol increase and decrease in channel catfish and sunshine bass exposed to acute confinement stressor. Comparative Biochemistry and Physiology. Toxicology and Pharmacology:CBP. 143:134-139. Interpretive Summary: Exposure of fish to a variety of stressful conditions results in an increase in plasma cortisol and glucose. High levels of cortisol which are maintained for an extended period of time can induce conditions unfavorable for the growth and survival of the fish, such as protein catabolism and immunosuppression. Little is known about the mechanism of cortisol decrease after exposure to stressful conditions. Metomidate is a new anesthetic which inhibits the synthesis and secretion of cortisol and was used to stop further cortisol synthesis after exposure to a low-water confinement stress in channel catfish and sunshine bass. The 15-minute confinement stress resulted in a much higher cortisol and glucose response in sunshine bass than in channel catfish. Plasma cortisol decreased immediately after the end of the stress and occurred more rapidly in channel catfish than in sunshine bass. Recovery in metomidate increased plasma clearance. These data indicate that cortisol secretion stops rapidly after the removal of the stress.
Technical Abstract: Channel catfish and sunshine bass were exposed to a low-water stress event and allowed to recover in fresh water or a solution of metomidate (dl-1-(1-phenylethyl)-5-(metoxycarbonyl) imidazole hydrochloride), which inhibits the synthesis of cortisol. Changes in plasma cortisol and glucose concentrations were used as indices of cortisol secretion and clearance. Plasma cortisol and glucose increased during the exposure to low-water stress in both fish, but the changes of both plasma components were more dramatic in sunshine bass. Exposure to metomidate during recovery resulted in a short-term increase in plasma glucose but differences between controls and metomidate-exposed fish were relatively minor thereafter. Cortisol began to decrease in catfish immediately after the removal of the stress but continued to increase for 15 min in sunshine bass recovering in fresh water and for 5 min in bass recovering in metomidate. Catfish recovering in fresh water had a cortisol clearance of -1.28 ng/ml/min compared with -2.45 ng/ml/min for fish recovering in metomidate (P>0.05) while sunshine bass recovering in fresh water had a clearance of -6.96 ng/ml/min compared with -4.50 ng/ml/min for fish recovering in metomidate (P>0.05). These data indicate that plasma cortisol decreases very rapidly in catfish and sunshine bass after the removal of the stressor.