Details

Autor(en) / Beteiligte

• Mitsuo Mita
• Uchida, Masaatsu K.

Titel

Muscarinic receptor binding and Ca 2+ influx in the all-or-none response to acetylcholine of isolated smooth muscle cells

Ist Teil von

• European journal of pharmacology, 1988-06, Vol.151 (1), p.9-17

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

1988

Link zum Volltext

Quelle

Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)

Beschreibungen/Notizen

• Isolated smooth muscle cells from guinea pig taenia caecum were prepared by collagenase digestion. Isolated single smooth muscle cells showed an all-or-none response to acetylcholine (ACh) under our experimental conditions. A Scatchard plot of the specific binding of [ 3H]quinuclidinyl benzilate (QNB) to the cells gave a straight line, and the K D and B max values were calculated as 0.18 ± 0.03 nM and 1.11 ± 0.10 pmol/mg protein, respectively. ACh competatively inhibited the specific binding of [ 3H]QNB in a concentration-dependent manner. Thus, although the cells showed an all-or-none response, ACh bound to the receptor concentration dependently. The contraction of the cells in response to ACh was inhibited in a concentration-dependent manner, by nicardipine suggesting that the contraction of smooth muscle cells in response to ACh depended on the influx of extracellular Ca 2+. The ACh-stimulated increase of the Ca 2+ influx was very rapid and correlated well with the contraction of the cells; it decreased after reaching a maximum. The all-or-none response of the cells could be due to a rapid influx of Ca 2+. These results suggest that ACh binds to its receptor in a concentration-dependent manner, and that when the binding reaches a certain threshold, a rapid influx of Ca 2+ occurs and the cells show an all-or-none response, followed by an efflux of Ca 2+.