Protein kinase C promotes spontaneous relaxation of streptolysin-O-permeabilized smooth muscle cells from the guinea-pig stomach.
Isolated single smooth muscle cells from the fundus of a guinea-pig stomach were permeabilized by use of streptolysin-O (0.5 U/ml). Most of the permeabilized cells responded to 0.6 microM Ca2+, but not to 0.2 microM Ca2+, with a resulting maximal cell shortening to approximately 71% of the resting cell length. These cells were relaxed again by washing with the Ca2+-free solution (2.5 nM free Ca2+) for 3-5 min. Addition of 10 microM acetylcholine (ACh) resulted in both a marked decrease in the concentration of Ca2+ required to trigger a threshold response and an increase in the maximal cell shortening, indicating that the cells retained the muscarinic receptor function. When the cell treated with a protein kinase C (PKC) inhibitor, K-252b (1 microM), for 3 min was exposed to 10 microM ACh in the presence of K-252b, the cell shortened within 2 min with a maximal cell shortening. When the cell shortening was induced by 10 microM ACh plus 1 microM Ca2+ in the presence of K-252b (1 microM) or more selective PKC inhibitors, such as calphostin C (1 microM) or PKC pseudosubstrate peptide (100 microM), the extension of the shortened cells, by washing with the Ca2+-free solution, was significantly inhibited. In contrast, K-252b (1 microM) did not inhibit the relaxation of Ca2+-induced shortened cells. These results suggest that the receptor-mediated activation of PKC in the process of ACh-induced cell shortening plays a role in the subsequent relaxation of the shortened cells.
Oishi
K
K
Department of Pharmacology, Meiji Pharmaceutical University, Tokyo, Japan. oishikz@my-pharm.ac.jp
Ishibashi
T
T
Nakamura
S
S
Mita
M
M
Uchida
M K
MK
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001426:Bacterial Proteins; D002118:Calcium / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D026121:Indole Alkaloids; D009126:Muscle Relaxation / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009281:Naphthalenes / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D013270:Stomach / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D013301:Streptolysins / Q000494:pharmacology
D001426:Bacterial Proteins; D002227:Carbazoles; D004791:Enzyme Inhibitors; D026121:Indole Alkaloids; D009281:Naphthalenes; D013301:Streptolysins; C025964:streptolysin O; C049985:staurosporine aglycone; D011493:Protein Kinase C; C058819:calphostin C; D000109:Acetylcholine; D002118:Calcium