Activities of sodium and potassium ions in epithelial cells of small intestine.
Intracellular molar Na(+) activity (a(Na)), measured with cation-selective glass microelectrodes, in epithelial cells of isolated bullfrog small intestine immersed at 26 degrees C in a sodium sulfate Ringer solution containing mannitol was 0.0144 +/- 0.0031 (average value plus or minus standard deviation). The corresponding K(+) activity (a(K)) was 0.0854 +/- 0.0060. Combination of these values with previous estimates of intracellular Na(+) and K(+) concentrations under identical conditions indicated that a substantial fraction of the cellular Na(+) is in an osmotically inactive state. When the cells were exposed to a Ringer solution in which 26 millimoles of mannitol per liter were replaced by 3-O-methyl glucose, highly significant decreases in a(K) and a(Na) were observed. The decrease in a(K) was proportionately larger than the corresponding decrease in a(Na).
D000818:Animals; D001001:Anura; D001693:Biological Transport, Active; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism / Q000502:physiology; D006027:Glycosides / Q000378:metabolism; D007421:Intestine, Small / Q000378:metabolism* / Q000502:physiology; D008297:Male; D008353:Mannitol / Q000378:metabolism; D008564:Membrane Potentials; D008839:Microelectrodes; D011188:Potassium / Q000378:metabolism*; D011892:Rana catesbeiana; D012964:Sodium / Q000378:metabolism*
D006027:Glycosides; D008353:Mannitol; D012964:Sodium; D011188:Potassium