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This Article Full Text Full Text (PDF) All Versions of this Article: 295/6/R1803    most recent 90590.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Stensløkken, K.-O. Articles by Vaage, J. Search for Related Content PubMed PubMed Citation Articles by Stensløkken, K.-O. Articles by Vaage, J.

ENDOCRINE PHYSIOLOGY AND METABOLISM

Differential regulation of AMP-activated kinase and AKT kinase in response to oxygen availability in crucian carp (Carassius carassius)

¹Department of Surgery, Ullevål University Hospital, ²Institute of Experimental Medical Research, Faculty Division Ullevål University Hospital, University of Oslo, ³Physiology Programme, Department of Molecular Biosciences, University of Oslo, ⁴Lillehammer University College, Oslo, Norway

Submitted 7 July 2008 ; accepted in final form 7 October 2008

We investigated whether two kinases critical for survival during periods of energy deficiency in anoxia-intolerant mammalian species, AMP-activated kinase (AMPK), and protein kinase B (AKT), are equally important for hypoxic/anoxic survival in the extremely anoxia-tolerant crucian carp (Carassius carassius). We report that phosphorylation of AMPK and AKT in heart and brain showed small changes after 10 days of severe hypoxia (0.3 mg O₂/l at 9°C). In contrast, anoxia exposure (0.01 mg O₂/l at 8°C) substantially increased AMPK phosphorylation but decreased AKT phosphorylation in carp heart and brain, indicating activation of AMPK and deactivation of AKT. In agreement, blocking the activity of AMPK in anoxic fish in vivo with 20 mg/kg Compound C resulted in an elevated metabolic rate (as indicated by increased ethanol production) and tended to reduce energy charge. This is the first in vivo experiment with Compound C in a nonmammalian vertebrate, and it appears that AMPK plays a role in mediating anoxic metabolic depression in crucian carp. Real-time RT-PCR analysis of the investigated AMPK subunit revealed that the most likely composition of subunits in the carp heart is ₂, β_1B, _2a, whereas a more even expression of subunits was found in the brain. In the heart, expression of the regulatory ₂-subunit increased in the heart during anoxia. In the brain, expression of the ₁-, ₂-, and ₁-subunits decreased with anoxia exposure, but expression of the ₂-subunit remained constant. Combined, our findings suggest that AMPK and AKT may play important, but opposing roles for hypoxic/anoxic survival in the anoxia-tolerant crucian carp.

metabolism; hypoxia; ATP; ADP; ethanol