Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: October 6, 2004
Publication Date: January 17, 2005
Citation: Welker, T.L., Klesius, P.H., Arias, C.R., Small, B.C. 2005. Effect of hypoxia on stress and heat shock protein expression in channel catfish (ictalurus punctatus rafinesque). Aquaculture America Conference. Technical Abstract: Channel catfish fingerlings were exposed to hypoxia (<2.0 mg/dL dissolved oxygen) for 4 h to determine the effect on the stress response. Fish were sampled prior to oxygen deprivation (0 h controls), after 2 and 4 h hypoxic exposure, and after 24 recovery under normoxic conditions. Fish subjected to hypoxia and normoxic controls were sampled at each time period, and plasma cortisol (primary stress response) and blood glucose (secondary stress response) were measured. In addition, gill, head kidney, and brain tissue were sampled to examine the effect of hypoxia on expression of heatshock proteins (Hsps) 60 and 70 (cellular stress response). Glucose (Fig. 1A) and cortisol (Fig. 1B) concentrations in fish increased significantly after exposure to hypoxia and returned to normoxic levels after the recovery period. Conversely, expression of Hsp 60 (Fig. 1C) and 70 (Fig. 1D) appeared to be generally down-regulated or unchanged in fish subjected to hypoxia compared to normoxic control fish; this trend did not change even after 24 h recovery. Differences in gene expression between normoxic and hypoxic fish were not significant. Because corticosteroids in part function to protect organisms against its normal defense reactions to stressors, high levels of cortisol released during stress may have inhibited induction of Hsps. Expression of Hsps 60 and 70 in channel catfish were not significantly affected by exposure to low-oxygen conditions, and therefore, would not be useful as a measure of hypoxia-induced stress. On the other hand, plasma cortisol and blood glucose both proved to be sensitive and reliable indicators of hypoxia-related stress. Measurement of blood glucose, as performed in this study, is a rapid, simple, and semi-invasive test capable of routine monitoring of stress in fish under most culture conditions.