Permeability properties and intracellular ion concentrations of epithelial cells in rat duodenum.
Effects of the K+ concentration in the bathing fluid ([K+]l) on the intracellular K+, Na+ and Cl- concentrations ([K+]i [Na+]i and [Cl-]i) as well as on the electrical potential were studied in rat duodenum. Changes in the mucosal K+ concentration ([K+]m), bringing the sum of Na+ and K+ concentrations to 147.2 mM constant, had little effect on the transmural potential difference (PDt), but did induce marked changes in the mucosal membrane potential (Vm). As [K+]m increased, Vm was depolarized gradually and obeyed the Nernst equation for a potassium electrode in the range of [K+]m greater than approx. 60 mM. Experiments of ion analyses were carried out on strips of duodenum to determine the effect of changing the external K+ concentrations on [K+] i, [Na+]i and [Cl-]i. An increase in [K+]o resulted in increases in [K+]i and [Cl-]i and a decrease in [Na+]i, [K+]i approaching its maximum at [K+]o greater than 70 mM. Such changes in [K+]i and [Na+]i seem to correlate quantitatively with the changes in [K+]o and [Na+]o. The values of the ratio of permeability coefficients, Pna+/PK+ were estimated using the Vm values and intracellular ion concentrations measured in these experiments. The results suggested that there appeared a rather abrupt increase in the PNa+/PK+ ratio from 0 to approx. 0.1, as [K+]m decreased.
D000818:Animals; D001693:Biological Transport, Active; D002463:Cell Membrane Permeability; D002712:Chlorides / Q000378:metabolism* / Q000494:pharmacology; D004386:Duodenum / Q000378:metabolism* / Q000502:physiology; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D007413:Intestinal Mucosa / Q000378:metabolism*; D008433:Mathematics; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000378:metabolism*
D002712:Chlorides; D012964:Sodium; D011188:Potassium