The Distribution of Sodium, Potassium and Chloride in the Smooth Muscle of the Rat Portal Vein

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Abstract
The contents of Na and K in isolated preparations of the rat portal vein were determined by micro flame photometry, and the distribution volumes of24Na,42K and36Cl in this vascular muscle were measured after incubation periods of variable duration. The results indicate the following total ion concentrations in the vessel wall: Na 94.5; K 51.2 and C1 100 meq/kg wet weight. Evidence was obtained for the existence of “bound” fractions of the three ions and a series of experiments was designed to determine the size of these extra compartments. Data from these experiments and measurements of total water and of extracellular space by sucrose‐14C allowed calculation of intracellular ion concentrations. The following values in meq/I intracellular fluid were obtained: [Na+]i 44.8; [K+]i 138 and [Cl‐]i 86.5. The equilibrium poten tials for the three ions would then be +30, ‐44 and ‐12 mV, respectively. Functional im plications of this ionic distribution are discussed.Measurements of total K contents and of extracellular space in portal vein preparations in cubated in hyperosmotic solution (Krebs +150 mmoles sucrose/l) indicated a clear‐cut in crease of [K+]i due to osmotic dehydration of the cells. A net loss of K seemed to occur with long periods of incubation in hyperosmotic solution.