Effects of excess free fatty acids on the electrophysiological properties of ventricular specialized conducting tissue: a comparative study between the sheep and the dog.

The effects of sodium palmitate were studied on the transmembrane potential properties of canine subendocardial Purkinje fibers and on the Purkinje fibers of the dog and the sheep false tendons with standard microelectrode technique. Following 4 h of superfusion with palmitate/albumin = 10, action potential duration in all preparations was prolonged (p less than 0.05), and resting membrane potential, action potential amplitude, and maximum rate of rise were slightly but significantly (p less than 0.05) diminished in the subendocardial preparation, but not in the false tendons. Action potential prolongation was reversible in the dog preparations but only partially reversible in the sheep Purkinje fibers. Following palmitate-induced prolongation of the action potential duration, rapid spontaneous diastolic depolarization was observed in the subendocardial Purkinje fibers. Palmitate enhanced spontaneous diastolic depolarization in the sheep but not in the dog Purkinje fibers (false tendons). Albumin alone had no effect on all action potential properties in both species. It is concluded that extended periods of exposure of the ventricular specialized conducting tissue to excess levels of palmitate can induce action potential abnormalities and subsequent rhythm disturbances both in the dog and the sheep.