Development of cardiovascular responses to hypoxia in larvae of the frog Xenopus laevis

The effects of acute hypoxia and changes in oxygen levels were analyzed in the developing cardiovascular systems of the African clawed frog, Xenopus laevis. The activity of the developing heart and vascular smooth muscles of the larval frogs was directly inhibited by hypoxia during the early Nieuwkoop-Faber (NF) stage. Furthermore, the cardiovascular responses to hypoxia that was exhibited by the larval frogs varied during the early NF and late NF stage.