Contribution of an electrogenic sodium pump to the membrane potential in rabbit sinoatrial node cells.
A study has been made of the transient hyperpolarization (K+-induced hyperpolarization) which developed following readmission of potassium after having pre-treated the rabbit sinoatrial node tissue with K+-depleted Tyrode solution for 4--5 min at 35 degrees C. Evidence is presented indicating that the K+-induced hyperpolarization results from the activity of an electrogenic sodium pump: The K+-induced hyperpolarization was inhibited by substituting Li+ for Na+ and by cooling the tissue. The amplitude of the K+-induced hyperpolarization was increased either by increasing K+ concentration in the recovery solution or by decreasing K+ concentration in the pre-treatment K+-depleted solution. By removing Cl- from the perfusates, the amplitude of the K+-induced hyperpolarization increased. In a Cl--depleted solution, the sinoatrial node cell membrane hyperpolarized by approximately 15 mV without a transient depolarization.
D000818:Animals; D001693:Biological Transport, Active; D002463:Cell Membrane Permeability; D002712:Chlorides / Q000494:pharmacology; D008094:Lithium; D008564:Membrane Potentials; D011188:Potassium; D011817:Rabbits / Q000502:physiology*; D012849:Sinoatrial Node / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*; D012996:Solutions
D002712:Chlorides; D012996:Solutions; D008094:Lithium; D012964:Sodium; D011188:Potassium