Effect of saccharin on the ATP-induced increase in Na+ permeability in isolated chicken intestinal epithelial cells.
When isolated intestinal cells from 3-wk-old chickens are treated with exogenous ATP they undergo a dramatic increase in permeability towards Na+. The increase occurs instantaneously and maximum cell loading with Na+ occurs within 2 min. The response is dose dependent (0.1-1.0 mM-ATP) and results in as much as a 10-fold increase in unidirectional influx of 22Na+ into the cells. The resting cellular Na+ gradient and membrane potential are partially dissipated and consequently Na+-dependent transport of sugars and amino acids is inhibited. Sodium saccharin (20 mM), added at the same time as ATP, completely blocks the effect of ATP on Na+ permeability and preserves the functional capacity of the cells for Na+-dependent sugar or amino acid transport. Partial protection is afforded by 10 mM-saccharin. Saccharin added 2 min after ATP will reverse the enhanced Na+ permeability that has already been induced. In cells that have not been treated with ATP, saccharin induces enhanced sugar and amino acid gradients (P less than 0.05 in paired comparisons from the same cell preparation), indicating that it may also inhibit Na+ permeability of the unperturbed membrane and allow cells to establish higher Na+ gradients and/or membrane potentials. The effect of saccharin in blocking ATP-induced Na+ permeability occurs within 10 sec and at a much lower dose than that required for blockade of facilitated diffusional sugar transfer in these cells.
Kimmich
G A
GA
Department of Biochemistry, School of Medicine and Dentistry, University of Rochester, NY 14642.
Randles
J
J
Anderson
R L
RL
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002645:Chickens; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects*; D012439:Saccharin / Q000494:pharmacology*; D012964:Sodium / Q000493:pharmacokinetics*
D000255:Adenosine Triphosphate; D012964:Sodium; D012439:Saccharin