Acetylcholine via Muscarinic Receptors Inhibits Histamine Release from Human Isolated Bronchi

Human bronchi were incubated in organ baths to measure histamine release. The calcium ionophore A23187 (10 μ mol/L; 1 min) stimulated histamine release by 148 ± 28% (n = 11) above the prestimulation level but was ineffective in epithelium-denuded bronchi. Neither bradykinin (0.1 μ mol/L) nor compound 48/80 (10 μ g/ml) triggered the release of histamine from epithelium-intact bronchi. Acetylcholine did not affect spontaneous histamine release (about 2 nmol/g × 5 min) but inhibited A23187-evoked histamine release in an atropine-sensitive manner. Already a concentration as low as 0.1 nmol/L acetylcholine was effective, the maximal inhibition (by 89%) occurred at 100 nmol/L, whereas a concentration of 10 μ mol/L acetylcholine was ineffective. Oxotremorine (1 nmol/L), a stable agonist at muscarinic receptors, suppressed stimulated histamine release completely. Physostigmine (0.1 μ mol/L), an acetylcholinesterase inhibitor, reduced A23187-evoked histamine release by 58%. Antihuman IgE antibody stimulated histam...