Apical membrane ionic channels in the rabbit cortical thick ascending limb in primary culture.
Cortical thick ascending limbs of Henle's loop (cTAL) were microdissected from rabbit kidneys and cultured in a hormonally-defined medium. The cultured cells grew as a monolayer and retained the morphological and biochemical characteristics of the original tubule. Cyclic AMP production of the cultured cells was increased by human calcitonin (x13) and parathyroid hormone (x2). The cultured epithelial developed a transepithelial potential of 4.1 +/- 1.3 mV that was orientated positively towards the apical compartment. The basolateral membrane of the cells exhibited a chloride conductance sensitive to diphenylamine 2-carboxylate (DPC) and the apical membrane a barium-sensitive K+ permeability. Patch clamp analysis conducted on the apical membrane of the cells revealed the presence of three types of ionic channel. The first is a large conductance Ca(2+)-activated K+ channel (95 pS). The second K+ channel has a much smaller conductance (18.3 pS) and is insensitive to Ca2+. It may represent the conductive pathway for K+ recycling into the lumen in the original tubule. The last channel is cation selective, does not discriminate between Na+ and K+ and was found to have a conductance of 20.5 pS. Channel activity required a high cytoplasmic calcium concentration (1 mM), and was blocked by ATP (10 microM) applied on its cytoplasmic face.
Merot
J
J
Département de Biologie Cellulaire et Moléculaire, Centre d'Etudes de Saclay, Gif sur Yvette, France.
Poncet
V
V
Bidet
M
M
Tauc
M
M
Poujeol
P
P
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002116:Calcitonin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004553:Electric Conductivity / Q000187:drug effects; D006593:Hexokinase / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating; D007672:Kidney Cortex / Q000502:physiology*; D007700:Kinetics; D007931:Leucyl Aminopeptidase / Q000378:metabolism; D008138:Loop of Henle / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D010281:Parathyroid Hormone / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011336:Probability; D011817:Rabbits; D012964:Sodium / Q000494:pharmacology; D019379:Teriparatide; D005723:gamma-Glutamyltransferase / Q000378:metabolism
D010281:Parathyroid Hormone; D010446:Peptide Fragments; D015221:Potassium Channels; D019379:Teriparatide; D002116:Calcitonin; D012964:Sodium; D000242:Cyclic AMP; D005723:gamma-Glutamyltransferase; D006593:Hexokinase; D000469:Alkaline Phosphatase; D007931:Leucyl Aminopeptidase; D002118:Calcium