Palytoxin effects through interaction with the Na,K‐ATPase in Xenopus oocyte

Abstract

Palytoxin (PTX) is known to bind to Na,K‐ATPase, to inhibit its activity, and to induce cation conductance, but the mechanism of these effects is still poorly understood. In Xenopus oocytes, PTX induced a large cation conductance, an effect that could be prevented or reversed by ouabain for oocytes expressing Xenopus Na,K‐pumps but not with those expressing Bufo Na,K‐pumps. In both cases patch‐clamp experiments demonstrated a 7–8 pS channel in the presence of PTX. A large PTX‐induced conductance could be observed with minimal Na,K‐pump inhibition. From the single PTX‐induced channel and macroscopic whole oocyte conductance, and the number of Na,K‐pumps, we can conclude that PTX‐induced conductance occurs through a direct interaction of PTX with a small number of Na,K‐pumps.