BASENJI-GREYHOUND DOG - INCREASED M(2) MUSCARINIC RECEPTOR EXPRESSIONIN TRACHEALIS MUSCLE

Airway smooth muscle from asthmatic humans and from the Basenji-greyho und dog (BG) dog is hyporesponsive to beta-adrenergic agonist stimulat ion. Because adenylyl cyclase is under dual regulation in airway smoot h muscle, we compared muscarinic receptor-coupled inhibition of adenyl yl cyclase in airway smooth muscle from BG and mongrel dogs. Inhibitio n of forskolin-stimulated adenylyl cyclase activity by the muscarinic M(2) agonist oxotremorine was greater in airway smooth muscle membrane s from BG compared with mongrel controls. Quantitative immunoprecipita tion studies showed increased numbers of m(2) but not m(3) muscarinic receptors in the BG airway smooth muscle. The enhanced ability of musc arinic agonists to inhibit adenylyl cyclase in BG airway smooth muscle may be due to the greater numbers of muscarinic m(2) receptors, which may account in part for impaired airway smooth muscle relaxation in t he BG model of airway hyperresponsiveness.