CHANNEL-SPECIFIC EFFECTS OF N-ALKYL SULFATE ONIONS ON 3 SHAKER-RELATED POTASSIUM CHANNELS EXPRESSED IN XENOPUS OOCYTES

n-Alkyl sulphate anions have been shown to reversibly affect the funct ioning of voltage-gated ion channels in a variety of preparations. The y are suggested to exert their effects by increasing the magnitude of the negative surface potential at the external face of the membrane. H ere we report the effects of n-octyl sulphate (OS-) and n-dodecyl sulp hate (DDS-) on RCK1 (Kv1.1), RCK4 (Kv1.4) and Shaker B potassium chann els exogenously expressed in Xenopus oocytes, Both OS- and DDS- produc ed a hyperpolarising shift in the activation voltage dependence of all three channels, consistent with an increased negative external surfac e potential. Similar kinetic changes were also observed, the kinetics of both activation and inactivation being accelerated in the presence of OS- and DDS-. However, we also found that while 10 mM OS- and 50 mu M DDS- significantly increased the maximum conductance of RCK1 and Sh aker B channels, 5 mM OS- and 15 mu M DDS- produced a large decrease i n RCK4 conductance; the possible involvement of RCK4 residue K533 in t his effect is discussed. Our data indicate that n-alkyl sulphate anion s can perturb ion channel function in a variety of ways and that their effects are complex and channel specific.