HIF-1α mRNA levels in Eurasian perch (Perca fluviatilis) exposed to acute and chronic hypoxia

The big advantage of using molecular biomarkers to monitor oxygen levels in aquatic systems is that responses at the molecular level tend to be more sensitive, and usually occur earlier than those at higher levels of biological organization Aquatic hypoxia is a frequent event, which can occur naturally in a variety of marine, estuarine and freshwater habitats. More often, however, hypoxia arises as a result of euthrophication of aquatic ecosystem and can lead to changes in community structure by eliminating hypoxia-sensitive species. Consequently fish have develop various physiological and biochemical mechanisms to cope with this environmental stress. Many of these adjustments depend to changes in expression of a wide range of genes. The transcriptional responses to hypoxia are primarily mediated by hypoxia-inducible factor-1 (HIF-1), a heterodimer composed of an alpha and beta subunit. This study investigated if HIF-1 alpha mRNA levels were regulated by hypoxia in Eurasian perch (Perca fluviatilis), a hypoxia-sensitive fresh water species. The real-time PCR was utilized to monitor dynamic changes in levels of HIF-1 alpha mRNA in response to acute (DO 0.4 +/- A 0.1 mg/l for 1 h) and chronic (DO 2.8 +/- A 0.3 mg/l for 15 days) hypoxia. Our results indicated an up-regulation of HIF-1 alpha in brain and liver, but not in muscle tissue after acute hypoxic treatment, whereas significant changes of HIF-1 alpha mRNA levels were detected in muscle, but not in brain and liver after chronic hypoxia exposure. This study suggests that HIF-1 alpha mRNA level in selected perch tissues could be an useful indicator of acute exposure to hypoxia.