Hypoxia inducible factor 1-α is minimally involved in determining the time domains of the hypoxic ventilatory response in adult zebrafish (Danio rerio)

Abstract

In the current study, adult zebrafish (Danio rerio) were exposed to 72 h hypoxia (90 mmHg) to assess the time domains of the hypoxia ventilatory response (HVR) and the consequence on a subsequent more severe (40 mmHg) bout of acute hypoxia. Experiments were performed on wild-type fish and mutants in which one or both paralogs of hypoxia inducible factor-1α (hif-1α) were knocked out. Although there were subtle differences among the wild-type and knockout fish, resting fV was reestablished after 2–8 h of continuous hypoxia in both groups, a striking example of hypoxic ventilatory decline (HVD). When fish were subsequently exposed to more severe hypoxia, a rapid increase in fV was observed, the magnitude of which was independent of genotype or prior exposure history. During recovery, fish that had been exposed to 72 h of 90 mmHg hypoxia exhibited a pronounced undershoot in fV, which was absent in the hif-1α double knockouts. Overall, the results revealed distinct time domains of the HVR in zebrafish that were largely Hif-1α-independent.