STRAIN-RELATED DIFFERENCES IN THE TRACHEAL RESPONSIVENESS OF SENSITIZED GUINEA-PIG

The purpose of this study was to evaluate the strain-related differenc es in tracheal hyperresponsiveness in control and egg albumen-sensitiz ed guinea pigs. Concentration-response curves to acetylcholine and bar ium chloride were established from tracheal rings of Dunkin-Hartley an d BFA strain guinea pigs. In the Dunkin-Hartley strain, sensitization did not significantly increase the tracheal responsiveness to acetylch oline and barium chloride. By contrast, in the BFA strain, significant sensitization-induced hyperreactivity was achieved as the maximal con tractions induced by acetylcholine and barium chloride, were enhanced from 6.5+/-1.2 and 3.2+/-0.4 mN in control to 10.0+/-1.4 and 5.6+/-0.8 mN, respectively, in sensitized animals. However, antigen challenge, performed in vitro, exhibited a similar amplitude of contraction in tr acheal rings from both strains (Dunkin-Hartley 5.1+/-0.8 mN; BFA 5.9+/ -0.5 mN). Finally, while the two guinea-pig strains developed specific sensitization to allergen, only tracheal rings from the BFA strain de veloped hyperresponsiveness to acetylcholine and barium chloride. The strain-related difference appears to be partly explained by a lower ba sal reactivity in the BFA strain both to acetylcholine (E(m) 7.3+/-1.7 and 6.5+/-1.2 mN for Dunkin-Hartley and BFA, respectively) and barium chloride (E(m) 9.4+/-2.6 and 3.2+/-0.4 mN for Dunkin-Hartley and BFA, respectively). As the same procedure of sensitization provides differ ent results in the genesis of hyperreactivity between the two guinea-p ig strains used for asthma models, the BFA guinea-pig strain seems to be a better model because sensitized non-challenged animals could easi ly be dissociated from control ones, similar to that which occurs in a sthmatic patients during provocation tests with cholinergic drugs.