Protein kinase C mediates the desensitization of CCh-activated nonselective cationic current in guinea-pig gastric myocytes.
The possibility of the protein kinase C (PKC) pathway being a mechanism underlying the desensitization of carbachol- (CCh-)activated nonselective cationic current (ICCh) was investigated in a study of guinea-pig gastric myocytes. Using the conventional whole-cell patch-clamp technique with symmetrical CsCl-rich solution in pipette and bath, ICCh was induced by bath application of 50 microM CCh. With 0.5 mM EGTA [ethyleneglycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] in the pipette solution (0.5 mM [EGTA]i), ICCh decayed spontaneously (desensitization of ICCh) to around 20% within 10 min. Desensitization of ICCh was significantly attenuated with 2 mM [EGTA]i. At a concentration of 20 microM OAG (1-oleoyl-2-acetyl-sn-glycerol), a PKC activator, inhibited ICCh at 0.5 mM [EGTA]i but far less at 2 mM [EGTA]i (18% and 81% of control, respectively). The same cationic current induced by intracellular guanosine-5'-O-(3-thiotriphosphate) (GTP[gamma-S]) was not inhibited by OAG with 0.5 mM [EGTA]i. The pretreatment of gastric myocytes with PKC inhibitors, either 1 microM chelerythrine or 1 microM peptide inhibitor, attenuated the desensitization of ICCh. [Ca2+]i was also measured by single cell microfluorometry using fura-2. Under CCh stimulation with 2 mM [EGTA]i, [Ca2+]i did not increase above 100 nM while it increased to around 260 nM with 0.5 mM [EGTA]i. These results suggest that the desensitization of ICCh is partly due to the Ca2+-dependent PKC pathway in guinea-pig gastric myocytes.
Kim
Y C
YC
Department of Physiology and Biophysics, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Korea.
Kim
S J
SJ
Sim
J H
JH
Jun
J Y
JY
Kang
T M
TM
Suh
S H
SH
So
I
I
Kim
K W
KW
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002217:Carbachol / Q000737:chemistry / Q000494:pharmacology*; D002412:Cations; D004075:Diglycerides / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D005260:Female; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006168:Guinea Pigs; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000502:physiology*; D010277:Parasympathomimetics / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013270:Stomach / Q000502:physiology*
D002412:Cations; D004075:Diglycerides; D007473:Ion Channels; D010277:Parasympathomimetics; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D004533:Egtazic Acid; C038237:1-oleoyl-2-acetylglycerol; D002217:Carbachol; D011493:Protein Kinase C; D002118:Calcium