Osmosensitivity of the hyperpolarization-activated chloride current in human intestinal T84 cells.
The osmosensitivity of the hyperpolarization-activated chloride current (I(Clhyp)) in T84 cells was studied using the whole cell patch-clamp recording configuration. Hypotonicity is known to activate an outwardly rectifying chloride current (HIORC) distinct from I(Clhyp) in these cells. The differing sensitivities of HIORC and I(Clhyp) toward inhibitors (1,9-dideoxyforskolin blocked HIORC but not I(Clhyp), and Cd2+ inhibited I(Clhyp) but not HIORC) allowed us to investigate the osmoregulation of I(Clhyp). Hypotonicity induced an increase in I(Clhyp) amplitude. Protein phosphatase inhibitors prevented this effect, and hypotonic solutions became slightly inhibitory. Hypertonicity resulted in a transient increase in I(Clhyp) amplitude followed by a large decrease. The complex responses of I(Clhyp) to osmotic changes indicate that these signals affect the same channel via multiple transduction pathways. The responses of I(Clhyp) to hypotonicity have features in common with the responses of ClC-2 channels expressed in Xenopus oocytes (activation) and with hyperpolarization-activated chloride currents in other cell types, such as osteoblasts and mandibular duct cells (inhibition).
Fritsch
J
J
Laboratoire du Calcium et Tissu Osseux dans l'Organisme en Développement, Centre National de la Recherche Scientifique Unité de Recherche Associée 583, Hôpital des Enfants Malades, Paris, France.
Edelman
A
A
D002478:Cells, Cultured; D018118:Chloride Channels / Q000502:physiology*; D002712:Chlorides / Q000502:physiology*; D006801:Humans; D007422:Intestines / Q000502:physiology*; D008564:Membrane Potentials; D019319:Okadaic Acid / Q000494:pharmacology; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000502:physiology
D018118:Chloride Channels; D002712:Chlorides; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases