Voltage-gated Ca2+ currents in rat gastric enterochromaffin-like cells.
Enterochromaffin-like (ECL) cells are histamine-containing endocrine cells in the gastric mucosa that maintain a negative membrane potential of about -50 mV, largely due to voltage-gated K+ currents [D. F. Loo, G. Sachs, and C. Prinz. Am. J. Physiol. 270 (Gastrointest Liver Physiol. 33): G739-G745, 1996]. The current study investigated the presence of voltage-gated Ca2+ channels in single ECL cells. ECL cells were isolated from rat fundic mucosa by elutriation, density gradient centrifugation, and primary culture to a purity > 90%. Voltage-gated Ca2+ currents were measured in single ECL cells using the whole cell configuration of the patch-clamp technique. Depolarization-activated currents were recorded in the presence of Na+ or K+ blocking solutions and addition of 20 mM extracellular Ca2+. ECL cells showed inward currents in response to voltage steps that were activated at a test potential of around -20 mV with maximal inward currents observed at +20 mV and 20 mM extracellular Ca2+. The inactivation rate of the current decreased with increasingly negative holding potentials and was totally abolished at a holding potential of -30 mV. Addition of extracellular 20 mM Ba2+ instead of 20 mM Ca2+ increased the depolarization-induced current and decreased the inactivation rate. The inward current was fully inhibited by the specific L-type Ca2+ channel inhibitor verapamil (0.2 mM) and was augmented by the L-type Ca2+ channel activator BAY K 8644 (0.07 mM). We conclude that depolarization activates high-voltage-activated Ca2+ channels in ECL cells. Activation characteristics, Ba2+ effects, and pharmacological results imply the presence of L-type Ca2+ channels, whereas inactivation kinetics suggest the presence of additional N-type channels in rat gastric ECL cells.
Bufler
J
J
Department of Neurology, Technical University of Munich, Germany.
Choi
G C
GC
Franke
C
C
Schepp
W
W
Prinz
C
C
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D019861:Enterochromaffin-like Cells / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005748:Gastric Fundus; D005753:Gastric Mucosa / Q000166:cytology; D006632:Histamine / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D014700:Verapamil / Q000494:pharmacology
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D001464:Barium; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D006632:Histamine; D014700:Verapamil; D002118:Calcium