COMPARATIVE-STUDY OF CARDIAC ELECTROPHYSIOLOGICAL EFFECTS OF ATRIAL-NATRIURETIC-PEPTIDE

The effects of atrial natriuretic peptide (ANP) on action potential ch aracteristics were studied in various (human, rabbit, guineapig) atria l and guinea-pig right ventricular papillary muscles. ANP (1-100 nM) d id not modify the resting membrane potential nor the maximum rate of d epolarization phase (V-max). Up to 10 nM, ANP dose-dependently decreas ed the action potential amplitude both in guinea-pig atrial and ventri cular muscles, but it did not affect this parameter in the other atria l preparations. ANP caused a dose-dependent, marked decrease of action potential duration (APD) in practically every cardiac preparation stu died (exception of guinea-pig left atrium). The strongest effect on AP D can be observed in human atrial and guinea-pig ventricular fibers. T he K+ channel blocker 4-aminopyridine (1 mM) and the ATP-dependent Kchannel inhibitor glibenclamide (10 mu M) prevented the effect of ANP on APD in both ventricular atrial preparations. ANP prevented the appe arance of isoprenaline (0.5 mu M) induced slow AP in K+ depolarized my ocardium. The present data suggest that ANP may inhibit the slow inwar d Ca2+ channel activity and facilitate the K+ channel activity.