Are electoneutral solutes using anion-selective channels with a low open-state probability at positive Vm values?
Several electrophysiologic studies have yielded data consistent with the hypothesis that the NPPs are formed from a single anion-selective channel type, having a low open-state probability at positive Vm values.3-5 Egée et al5 reported that the open-state probability of a malarial parasite-induced anion channel is 0.3 at 10 mV and less than 0.1 above +10 mV. Similar values have also been reported for an infection-induced anion channel in Plasmodium knowlesi infected monkey RBCs.24 Therefore, if electroneutral solutes also use this type of channel (as would be the case if the NPPs are formed by this channel type alone), their transport would be expected to reduce by some degree after membrane depolarization (because of the decreased open-state probability of the channels). Here, the transport of the electroneutral solute sorbitol via the NPPs in infected RBCs (in conditions that maintain a physiologic Vm negative of 0 mV) is consistent with previous reports (see “Are the data comparable
