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J Comp Physiol B. 2006 May;176(4):359-69. Epub 2005 Dec 14.

HIF-1alpha and iNOS levels in crucian carp gills during hypoxia-induced transformation.

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Department of Molecular Biosciences, University of Oslo, 1041, 0316, Oslo, Norway.


Hypoxia inducible factor 1 alpha (HIF-1alpha) initiates expression of a wide variety of genes, some of which are involved in apoptosis and cell cycle arrest. We have previously shown that crucian carp increases its respiratory surface area 7.5-fold in response to hypoxia. This change is due to apoptosis and cell cycle arrest in specific parts of its gills. Here we have characterized crucian carp HIF-1alpha, and measured mRNA, protein and DNA binding levels during hypoxia exposure in crucian carp gills. We have also measured an HIF-1alpha-induced gene, the inducible nitric oxide synthase (iNOS), which has the ability to initiate apoptosis and cell cycle arrest. Crucian carp HIF-1alpha was found to have all critical domains known to be important for function. Comparison of the peptide sequence with other species indicated high similarity with other cyprinid fish, but a pronounced variation compared to the salmonid, rainbow trout. Further, we found HIF-1alpha protein to be stabilized during hypoxia. Further, HIF-1alpha was often present in normoxia, and showed marked individual weight-dependent variation. We found no alteration of iNOS mRNA levels during hypoxia exposure. These findings suggest HIF-1alpha involvement in hypoxia-induced change of respiratory surface area in crucian carp gills. However, its activity does not seem to be mediated through iNOS.

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