Strain-related differences in the tracheal responsiveness of sensitized guinea pig

The purpose of this study was to evaluate the strain-related differences in tracheal hyperresponsiveness in control and egg albumen-sensitized guinea pigs. Concentration-response curves to acetylcholine and barium chloride were established from tracheal rings of Dunkin-Hartley and BFA strain guinea pigs. In the Dunkin-Hartley strain, sensitization did not significantly increase the tracheal responsiveness to acetylcholine and barium chloride. By contrast, in the BFA strain, significant sensitization-induced hyperreactivity was achieved as the maximal contractions 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 tracheal 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 developed hyperresponsiveness to acetylcholine and barium chloride. The strain-related difference appears to be partly explained by a lower basal reactivity in the BFA strain both acetylcholine (Em 7.3 +/- 1.7 and 6.5 +/- 1.2 mN for Dunkin-Hartley and BFA, respectively) and barium chloride (Em 9.4 +/- 2.6 and 3.2 +/- 0.4 mN for Dunkin-Hartley and BFA, respectively). As the same procedure of sensitization provides different results in the genesis of hyperreactivity between the two guinea-pig strains used for asthma models, the BFA guinea-pig strain seems to be a better model because sensitized non-challenged animals could easily be dissociated from control ones, similar to that which occurs in asthmatic patients during provocation tests with cholinergic drugs.