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Title: HYPOXIC CONDITIONS INDUCE HSP70 PRODUCTION IN THE BLOOD, BRAIN AND HEAD KIDNEY OF JUVENILE NILE TILAPIA OREOCHROMIS NILOTICUS(L.)

Author
item Delaney, Mary
item Klesius, Phillip

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2003
Publication Date: 2/25/2004
Citation: Delaney, M.A., Klesius, P.H. 2004. Hypoxic conditions induce hsp70 production in the blood, brain and head kidney of juvenile nile tilapia oreochromis niloticus(l.). Aquaculture.

Interpretive Summary: Many freshwater and coastal water bodies do not have enough dissolved oxygen to provide a healthy environment for fish and other aquatic life. This lack of oxygen can cause stress in these organisms. Lack of sufficient oxygen (hypoxia) causes fish to send available oxygen to critical organs, reduce energy metabolism, and increase the supply of energy by using alternate energy sources. In addition, fish and other organisms have the ability to begin producing or increase the production of special proteins, known as heat shock or stress proteins, in response to many different types of environmental stress. These proteins are distinguished by their molecular weight, and the best known of these proteins is a 70 kilo-dalton protein (Hsp70). We evaluated the cellular stress response by measuring Hsp70 protein levels in blood, brain, liver, muscle and head kidney tissues of juvenile Nile tilapia, subjected to low dissolved oxygen for 48 h. A highly significant increase in Hsp70 was detected in blood, brain, and muscle tissues in fish exposed to hypoxia compared to the control treatment, but no differences were observed among treatments in liver and head kidney tissues. To evaluate the physiological stress response, glucose and cortisol were measured. A highly significant increase was detected for serum glucose levels due to hypoxia treatments, but no differences were detected among serum cortisol levels. Results of this study show that inducible cellular stress responses can be measured in terms of Hsp70 using the blood, brain and muscle of tilapia exposed to chronic hypoxic conditions.

Technical Abstract: The levels of constitutive and inducible heat shock protein 70 (Hsp70) was measured in blood, brain, liver, muscle and head kidney tissues of juvenile Nile tilapia Oreochromis niloticus (L.), subjected to increasingly severe hypoxic stress (dissolved oxygen ~ 4.9 - 0.1 mg L-1) for 48 h. A highly significant increase in Hsp70 (*P<0.0001) was detected in blood, brain, and muscle tissues in fish exposed to hypoxia compared to those of fish in normal oxygenation treatment. No differences were observed among treatments in liver and head kidney tissues. A highly significant increase was detected for serum glucose levels due to hypoxia treatments, but no differences were detected among serum cortisol levels. Results of this study show that inducible cellular stress responses in terms of Hsp70 can be measured in the blood, brain and muscle of tilapia exposed to chronic hypoxic conditions.