Hypotonic swelling increases L-type calcium current in smooth muscle cells of the human stomach.
The purpose of the present study was to characterize the Ca2+ channels in smooth muscle cells from human stomach and to examine the effects of osmotic swelling on the channel activity. Ca2+ channel current with either Ca2+ or Ba2+ as charge carrier was recorded from freshly isolated smooth muscle cells using the conventional whole-cell patch clamp technique. The degree of cell swelling as a result of hypotonic challenge was monitored using a video image analysis system. The changes in intracellular Ca2+ concentration ([Ca2+]i) were measured by microfluorimetry. The pharmacological and voltage activation profile suggests a typical dihydropyridine-sensitive L-type Ca2+ current. Cell swelling, induced by hypotonic challenge, enhanced the amplitude of currents through L-type Ca2+ channels without significant effects on steady-state voltage dependency. After treatment with the L-type Ca2+ channel agonist Bay K 8644 (0.1-2 microM), no further significant increase in calcium channel current or corresponding [Ca2+]i transients were provoked by the swelling. The above results demonstrated that the presence of L-type Ca2+ current in smooth muscle cells of the human stomach and the augmentation of the current are closely associated with the volume increase resulting from hypotonic swelling.
Kim
C H
CH
Department of Physiology, Medicine and Surgery, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea.
Rhee
P L
PL
Rhee
J C
JC
Kim
Y I
YI
So
I
I
Kim
K W
KW
Park
M K
MK
Uhm
D Y
DY
Kang
T M
TM
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D001464:Barium / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism*; D048429:Cell Size; D002478:Cells, Cultured; D004095:Dihydropyridines / Q000494:pharmacology; D004553:Electric Conductivity; D005470:Fluorometry; D005753:Gastric Mucosa / Q000378:metabolism*; D006801:Humans; D007038:Hypotonic Solutions; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009997:Osmotic Pressure; D018408:Patch-Clamp Techniques; D013270:Stomach / Q000166:cytology / Q000187:drug effects / Q000502:physiology
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D004095:Dihydropyridines; D007038:Hypotonic Solutions; D001464:Barium; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C038806:1,4-dihydropyridine; D002118:Calcium