Changes in Stanniocalcin-2 and Hypoxia-Inducible Factor-la mRNA Expression in Medaka Oryzias dancena Exposed to Acute Hypoxia

摘要

Some fish live in aquatic environments with low or temporally changing O_2 availability. Variation in dissolved oxygen (DO) levels requires behavioral, physiological, and biochemical adaptations to ensure the uptake of sufficient O_2. Several speciesare relatively well adapted to tolerate low O_2 partial pressures (hypoxia). The medaka (Oryzias dancena) is an important model organism for biomedical research that shows remarkable tolerance to hypoxia. We investigated the regulation and role of hypoxia-inducible factor-1 (HIF-1alpha) as a general hypoxia-response gene and stanniocalcin-2 (STC2), which is one of the genes regulated by HIF-la in mammals under hypoxia. We subjected adult male medaka to the following three acute hypoxia regimes: 1, 24, and 72 h at DO = 1.8±0.5 ppm. The changes in STC2 and HIF-1alpha mRNA were monitored using quantitative real-time reverse-transcription PCR. We found strong upregulation of HIF-lalpha mRNA in the livers of fish exposed to hypoxia. Hypoxia rapidly upregulated STC-2 mRNA expression in muscle, but not in the brain, gills, liver, or intestine. Therefore, unlike in mammals, hypoxia might regulate O. dancena STC-2 expression in an HIF-la-independent manner.