Effect of Ca2+ deprivation on short-term desensitization of isolated smooth muscle cells showing an all-or-none response to acetylcholine.
1. Short-term desensitization of the contractile response of isolated smooth muscle cells from guinea pig taenia caecum to acetylcholine was examined in the absence of external Ca2+. 2. Isolated smooth muscle cells contracted to 10(-7)-10(-6) M acetylcholine, showing an all-or-none response. 3. Desensitization was induced by incubating the cells with 10(-4) M acetylcholine for 10 min in Ca2+-free solution. 4. Desensitized cells showed an all-or-none response but required a higher concentration of acetylcholine for induction of contraction, indicating that the desensitization was due to a change in the threshold concentration. 5. Desensitization is suggested to be induced before massive influx of Ca2+ into the cells.
Department of Molecular Pharmacology, Meiji College of Pharmacy, Tokyo, Japan.
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M
Mita
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Matsuo
M K
MK
Uchida
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002432:Cecum / Q000187:drug effects; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects*; D013997:Time Factors
D000109:Acetylcholine; D002118:Calcium