Cholinesterase activity is similar in C3H/HeJ and A/J mice and does not account for their different bronchoconstrictor responsiveness

Significant interstrain variation in airway responsiveness to acetylcholine (ACh) exists in inbred mouse strains. We hypothesized that part of the var iation may be due to between-strain differences in cholinesterase activity. We asked if administration of neostigmine (an acetylcholinesterase inhibit or) and/or succinylcholine (an agent which competes for and inhibits butyry lcholinesterase) altered ACh responsiveness in hyporesponsive C3H/HeJ and h yperresponsive A/J mouse strains. Airway responses to ACh were measured by the airway pressure time index in the presence and absence of succinylcholi ne (10 mg/kg) and/or neostigmine (0.7 mg/kg). In addition, acetylcholineste rase and butyrylcholinesterase activity mere directly measured. Acetylcholi nesterase and butyrylcholinesterase inhibition increased airway responses t o acetylcholine in both strains, but did not eliminate or decrease the diff erences in airway responsiveness to ACh previously seen in the two strains. Cholinesterase activities in the two strains were not significantly differ ent. We conclude that differences in either acetylcholinesterase or butyryl cholinesterase in the A/J or C3H/HeJ mouse strains are unlikely to contribu te to the differences in airway responsiveness to exogeneously administered cholinergic agonists.