Vasopressin and water permeability of artificial lipid membranes

Abstract

Vasopressin markedly stimulated the water permeability of bilayer lipid membranes: a two-fold increase was measured at 25° in presence of 1.7·10 −9 M (50 μunits/ml) vasopressin. Oxytocin and a mixture of the amino acids comprising the vasopressin molecule could not substitute for vasopressin at comparable concentration. The experimental activation energy of water transport was reduced in the presence of vasopressin from 14 to 4 kcal/mole, in agreement with the effect of the hormone on water permeability of toad bladder.