Fatty acid modifies Ca²⁺-dependent potassium channel activity in smooth muscle cells from the human aorta

By using the patch–clamp technique the effect of 2-decenoic acid (DA) on Ca²⁺-activated potassium (K⁺) channels in the membrane of smooth muscle cells from the human aorta was studied. In the presence of 0.5 μM Ca²⁺ and 2 mM Mg²⁺ on the cytoplasmic side of the membrane, a more than tenfold elevation in the probability of the channels being open (p_o) was observed under the effect of DA. With divalent cation concentrations of less than 1 nM DA caused a more than twofold elevation in p_o. In the DA-treated membranes Mg²⁺ ions, which normally fail to activate the channels, brought about a nearly threefold increase in the channel activity when applied to the inner membrane surface. Channel sensitivity to the activating effect of cytoplasmic Ca²⁺ ions did not increase with the application of DA. Single-channel conductance was unchanged by DA exposure. We suggest that DA alters the Ca²⁺-binding mechanism of the channel, increasing its sensitivity to Mg²⁺ ions, presumably owing to membrane fluidization.