The undirectional transcutaneous fluxes of Na, Cl, water and urea were measured, in vitro, in the pipoid anuran Xenopus laevis. An active uptake (outside to inside) of Na was observed but Cl movements appeared to be passive. The effluxes of Na and Cl were low compared to those measured in other species of amphibians. The active Na transport was less than that of more terrestrial species and, although it could be stimulated by vasotocin, aldosterone was ineffective. The permeability of the skin to water was also low and although it was increased in the presence of vasotocin the magnitude of the response was much less than seen in more terrestrial anurans. The skin was permeable to urea but the movement of this solute was not remarkable when compared to that in other amphibians. These properties of the skin are discussed in relation to the animal's aquatic manner of life.
Animals Biological Transport, Active