Rectifier properties of canine papillary muscle.

Abstract

1. The membrane properties of canine papillary muscle were investigated using a sucrose gap and glass microelectrodes.2. Replacement of chloride by large anions had little effect on the resting potential but reduced the resting membrane conductance by 30%. It was suggested that the chloride permeability remained almost unchanged when the membrane was hyperpolarized.3. When a constant hyperpolarizing current was passed across the membrane, the membrane conductance fell slowly to a certain level, and returned to its initial level in a few seconds after the end of the current.4. Similar changes in conductance during hyperpolarization were also observed in chloride-deficient or sodium-deficient solution.5. Conditioning hyperpolarization greatly affected the magnitude and the time course of the electrotonic potential produced by the second pulse of hyperpolarizing current, whereas conditioning depolarization had little effect.6. The region of high resistance in the current-voltage relation extended to more negative potentials in 1.34mm [K] 0 than in 2.68mm [K] 0.7. The current-voltage relations both in 0.27mm [K] 0 and in glycerolhypertonic solution showed persistently high resistance at any membrane potential investigated (from-50mV to-150mV). The slow potential change during hyperpolarization disappeared in these solutions.8. The results are interpreted as indicating that:(a) A delayed rectifier system for potassium current exists in the potential region more negative than the resting potential.(b) The potassium permeability of canine papillary muscle rises when potassium ions move inward across the membrane and falls when they move outward (anomalous rectification).