CAT HEART MUSCLE IN VITRO. 8. ACTIVE TRANSPORT OF SODIUM IN PAPILLARY MUSCLES.
The cells of cat right ventricular papillary muscles were depleted of K and caused to accumulate Na and water by preincubation at 2-3 degrees C. The time courses of changes in cellular ion content and volume and of the resting membrane potential (V(m)) were then followed after abrupt rewarming to 27-28 degrees C. At physiological external K concentration ([K](o) = 5.32 mM) recovery of cellular ion and water contents was complete within 30 minutes, the maximal observable rates of K uptake and Na extrusion (Deltammol cell ion/(kg dry weight) (min.)) being 3.4 and 3.6, respectively. The recovery rate was markedly slowed at [K](o) = 1.0 mM. Rewarming caused V(m) measured in cells at the muscle surface to recover within from <1 to 9 minutes, but only slight restoration of cellular ion contents (measured in whole muscles) had occurred after 10 minutes. Studies of recovery in NaCl-free sucrose Ringer's solution made it possible to separate the ouabain-insensitive outward diffusion of Na as a salt from a simultaneous ouabain-sensitive Na extrusion which is associated with a net cellular K uptake. A hypothesis consistent with these observations is that rewarming may activate a ouabain-sensitive "electrogenic" mechanism, most probably the net active transport of Na out of the cell, from which net K uptake may then follow passively.
D001692:Biological Transport; D001693:Biological Transport, Active; D002415:Cats; D004594:Electrophysiology; D066298:In Vitro Techniques; D007477:Ions; D008564:Membrane Potentials; D009132:Muscles; D010042:Ouabain; D010210:Papillary Muscles; D010600:Pharmacology; D010827:Physiology; D011188:Potassium; D012106:Research; D012964:Sodium; D012965:Sodium Chloride; D013395:Sucrose; D013696:Temperature
D007477:Ions; D012965:Sodium Chloride; D013395:Sucrose; D010042:Ouabain; D012964:Sodium; D011188:Potassium
BIOLOGICAL TRANSPORT; CATS; ELECTROPHYSIOLOGY; EXPERIMENTAL LAB STUDY; OUABAIN; PAPILLARY MUSCLES; PHARMACOLOGY; PHYSIOLOGY; POTASSIUM; SODIUM; SODIUM CHLORIDE; SUCROSE; TEMPERATURE