SPERMINE AND SPERMIDINE AS GATING MOLECULES FOR INWARD RECTIFIER K+ CHANNELS

Inward rectifier K+ channels pass prominent inward currents, while out ward currents are largely blocked. The inward rectification is due to block by intracellular Mg2+ and a Mg2+-independent process described a s intrinsic gating. The rapid loss of gating upon patch excision sugge sts that cytoplasmic factors participate in gating. ''intrinsic'' gati ng can be restored in excised patches by nanomolar concentrations of t wo naturally occurring polyamines, spermine and spermidine. Spermine a nd spermidine may function as physiological blockers of inward rectifi er K+ channels and ''intrinsic'' gating may largely reflect voltage-de pendent block by these cations.