Hypoxia inducible factor 1α, hypoxanthine‐guanine phosphoribolsyl transferase and NADPH oxidase 4 from northern elephant seals: cDNA characterization and tissue expression

Abstract

Northern elephant seals (Mirounga angustirostris) are naturally adapted to prolonged periods (1–3 months) of food deprivation (fasting) and tissue ischemia. Fasting elephant seal pups do not exhibit signs of oxidative damage or inflammation despite increases in the renin‐angiotensin system, NADPH oxidase activity and the superoxide‐generating enzyme, NADPH oxidase 4 (Nox4). Inducible factor 1α (HIF‐1α) and hypoxanthine‐guanine phosphoribosyl transferase (HGPRT) may be activated in response to fasting‐ and hypoxia‐induced increases in ROS. We report the molecular characterization and tissue expression of Nox4, HIF‐1α and HGPRT from fasting northern elephant seal pups. The full‐length sequence for HGPRT is 761 bp long and codes for 218 amino acids, which is similar to other mammalian homologs. The partial sequences of Nox4 and HIF‐1α are 1131 bp and 745 bp long respectively and correspond to approximately 65% and 35% of the full sequence of mammalian homologs, respectively. HGPRT, Nox4 and HIF‐1α sequences are similar to vertebrate homologs and contain conserved functional and regulatory domains. HGPRT, Nox4 and HIF‐1α expression was detected in both muscle and adipose tissue, with higher expression in muscle than in adipose. The present study represents a critical first step towards advancing our understanding of the molecular mechanisms of oxidant regulation in response to prolonged fasting and apnea‐induced ischemia.