title: Insulin activates single amiloride-blockable Na channels in a distal nephron cell line (A6).
abstract: Using the patch-clamp technique, we studied the effect of insulin on an amiloride-blockable Na channel in the apical membrane of a distal nephron cell line (A6) cultured on permeable collagen films for 10-14 days. NPo (N, number of channels per patch membrane; Po, average value of open probability of individual channels in the patch) under baseline conditions was 0.88 +/- 0.12 (SE)(n = 17). After making cell-attached patches on the apical membrane which contained Na channels, insulin (1 mU/ml) was applied to the serosal bath. While maintaining the cell-attached patch, NPo significantly increased to 1.48 +/- 0.19 (n = 17; P less than 0.001) after 5-10 min of insulin application. The open probability of Na channels was 0.39 +/- 0.01 (n = 38) under baseline condition, and increased to 0.66 +/- 0.03 (n = 38, P less than 0.001) after addition of insulin. The baseline single-channel conductance was 4pS, and neither the single-channel conductance nor the current-voltage relationship was significantly changed by insulin. These results indicate that insulin increases Na absorption in the distal nephron by increasing the open probability of the amiloride-blockable Na channel.
authors.affiliation: Hospital for Sick Children Research Institute, Ontario, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Marunaka
authors.forename: N
authors.initials: N
authors.lastname: Hagiwara
authors.forename: H
authors.initials: H
authors.lastname: Tohda
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D004594:Electrophysiology; D007328:Insulin / Q000494:pharmacology*; D009399:Nephrons / Q000166:cytology / Q000378:metabolism*; D015222:Sodium Channels / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D013997:Time Factors
chemical_list: D007328:Insulin; D015222:Sodium Channels; D000584:Amiloride