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The effect of polyamines on K_ATP channels in guinea-pig ventricular myocytes

X. W. Niu and R. W. Meech

1. The effect of natural polyamines on K_ATP channels was studied using inside-out patches from guinea-pig ventricular myocytes.

2. At a holding potential of +40 mV, spermine at the intracellular membrane surface reduced the K_ATP channel open probability (P_open) in a dose-dependent manner. Half-maximal inhibition occurred at 29 µM with a Hill coefficient of 1·2.

3. The effect of spermine on P_open was not greatly influenced by the membrane potential but there appeared to be a small reduction in unitary current amplitude during strong depolarizations.

4. Analysis of K_ATP single channel kinetics showed that spermine inhibited the channel by decreasing the mean open time and introducing transitions to a long closed state.

5. Spermidine (0·1 mM) was found to have a similar effect to spermine. Putrescine (10 mM) was found to block more effectively at positive membrane potentials. Up to 20 mM arginine had no significant effect on K_ATP channels.

6. Our results indicate that natural polyamines influence native K_ATP channel gating in cardiac myocytes.

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