Effects of arginine vasotocin on water balance of three leiopelmatid frogs

Abstract

The effects of arginine vasotocin (AVT) on water movements in three frogs of the anatomically primitive genus Leiopelma were compared in vivo and in vitro. Treatment with AVT in vivo (7 x 10(-13) mol/g body weight) led to significant water retention in the terrestrial species L. archeyi and L. hamiltoni, but not in the semiaquatic species L. hochstetteri. All three species showed increasing water retention over some part of the dose range 7 x 10(-15)-7 x 10(-11) mol/g. Isolated pelvic skin from L. archeyi and L. hamiltoni increased in osmotic water flow (OWF) in response to AVT, whereas that from L. hochstetteri did not. Dorsal skin from all three species, as well as pectoral skin from L. archeyi and L. hochstetteri, showed no hydroosmotic response to AVT. Isolated bladders of all species are small and showed small increases in OWF in response to AVT. Glomerular filtration rate in vivo was reduced significantly by AVT in L. archeyi and L. hamiltoni, but not in L. hochstetteri. These results show that water balance responses to AVT among the three species are correlated with habitat, and indicate that the absence of a cutaneous hydroosmotic response in L. hochstetteri is not a characteristic, primitive feature of the entire genus.