Ischemic poison lysophosphatidylcholine modifies heart sodium channels gating inducing long-lasting bursts of openings

The effects of lysophosphatidylcholine (LPC) on Na channels in inside-out patches of adult rat ventricular cells using the patch-clamp technique have been investigated. Application of LPC (9–25 M) from the inner side of membrane for 4–15 min caused a reduction of averaged Na current (I_Na) peak and prolonged the time course of inactivation in the potential range of -50 to -10 mV. Analysis of single channel behaviour revealed that after 30–50 min of exposure, in addition to normally functioning Na channels with short openings, LPC induced longlasting bursts of Na channel openings (up to the 300 ms duration of the test pulses). This resulted in an appearance of noninactivated component of I_Na. The slope conductance of these modified channels remained the same as in control (11.3 pS — control; 11.6 pS — LPC-treated). The dwell time for modified channels increased significantly.