Figure 7.

[³H]-NMS binding to human airway smooth muscle muscarinic receptors occupied by glycopyrrolate and ipratropium bromide. Human airway membranes were treated with the assay buffer (Control) or the test antagonists (each at 30 nM) for 3 h at 30°C. After this preincubation period, the volume of membrane suspension was then diluted (in order to induce antagonist dissociation) with the assay buffer containing final [³H]-NMS concentration of 0.5 nM. The association of [³H]-NMS (expressed as percentage inhibition of [³H]-NMS binding which reflect the percentage of glycopyrrolate or ipratropium occupied receptors) was measured at appropriate time intervals. Specific [³H]-NMS binding in the presence of the antagonists was corrected for protein concentration and expressed as a percentage of that obtained for binding to control membranes. Values are means±s.e.mean from three independent experiments performed in duplicate on separate membrane preparations.