Glucosensing in an immortalized adrenomedullary chromaffin cell line: role of ATP-sensitive K+ channels.
Using an immortalized adrenal chromaffin cell line (MAH cells), we investigated the cellular mechanisms underlying sensitivity to glucose-free solution (aglycemia) using ratiometric Ca2+ imaging and whole-cell recording. Though few cells (< 15%) responded to aglycemia with an increase in intracellular-free Ca2+ concentration ([Ca2+]i), in most cells (approximately 75%), aglycemia caused > 50% suppression of the Delta[Ca2+]i induced by the depolarizing stimulus, high (10 mM) K+. Moreover, in normal K+, the average aglycemia-induced rise in Cai2+ as well as the proportion of aglycemia-responsive cells increased in the presence of the K(ATP) channel blocker, glibenclamide. During membrane potential (Vm) measurements, aglycemia induced either hyperpolarization (6/20), depolarization (4/20) or no change in Vm. RT-PCR and Western blotting confirmed the presence of K(ATP) channel subunits Kir6.2 and SUR1 in MAH cells. These findings suggest a dual inhibitory and excitatory action of aglycemia in MAH cells, where activation of K(ATP) channels effectively inhibits or blunts the Delta[Ca2+]i due to the excitatory effect. Thus, this cell line appears as an attractive model for studying the molecular mechanisms of glucosensing.
Piskuric
Nikol A
NA
Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1. piskurn@mcmaster.ca
Brown
Stephen T
ST
Zhang
Min
M
Nurse
Colin A
CA
D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002461:Cell Line, Transformed; D019439:Chromaffin Cells / Q000187:drug effects / Q000502:physiology*; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D011188:Potassium / Q000494:pharmacology; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011955:Receptors, Drug / Q000235:genetics / Q000378:metabolism*; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel
D018528:ATP-Binding Cassette Transporters; D002118:Calcium; D005947:Glucose; D005905:Glyburide; D007004:Hypoglycemic Agents; D011188:Potassium; D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel; C577509:Abcc8 protein, rat