Muscarinic and beta-adrenergic receptor expression in peripheral lung from normal and asthmatic patients

We used human peripheral lung from 8 mildly asthmatic patients and 11 normal donors to study the expression of muscarinic and beta-adrenergic receptors in asthma. There was no significant difference in the affinity or the density of muscarinic (labeled with [N-methyl-3H]scopolamine) and beta 1- and beta 2-adrenergic receptors (labeled with [125I]iodocyanopindolol) in peripheral lung from asthmatics compared with nonasthmatics. Only the muscarinic m1 receptor mRNA was detected in human lung using Northern blot analysis. Additionally, peripheral lung cellular mRNA hybridized to human beta 1 and beta 2 cDNA probes, giving 3.2- and 2.2-kb hands corresponding to beta 1 and beta 2-adrenergic receptors mRNA, respectively. Densitometric scanning of the autoradiograms suggests that there was no significant difference in the relative abundance of muscarinic m1 and beta 1- and beta 2-adrenergic receptor mRNA in asthmatic compared with nonasthmatic lungs. Functional experiments obtained in trachea suggest that there was an increase in the cholinergic neural response evoked by electrical field stimulation in asthmatic compared with nonasthmatic tissues which was not due to a reduction in inhibitory noncholinergic nonadrenergic relaxations.