Changes in the reactivity of the ileum (to histamine and barium chloride) and vas deferens (to acetylchohne and barium chloride), isolated from actively egg albumen-sensitized guinea pigs, have been investigated. The study was performed on 2 guinea pig strains: the Dunkin-Hartley strain, usually used as an airway allergic model, and the BFA strain. In actively sensitized guinea pigs of both strains, concentration-response curves exhibited a significant dose-dependent upward shift compared to those obtained in control guinea pigs. The maximal contraction strength calculated from these curves was significantly enhanced in both sensitized guinea pig strains, without a change in EC₅₀ values. This study showed that the active antigen sensitization procedure involved several smooth muscle functions, and not exclusively the trachea.

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The present results show that the in vitro application of purified IgG1 can produce non-specific smooth muscle hyperreactivity and hypersensitivity. So, IgG1 can be considered as the main factor involved in the genesis of sensitization-induced hyperresponsiveness, and probably play a great role in hyperreactivity observed during allergic diseases and anaphylaxis.

Isolated mouse vas deferens preparations were used to study the effect of temperature on noradrenaline-induced contractions. Preparations were suspended in the organ bath containing Krebs-Henseleit solution for isometric tension recording. Contractile responses to noradrenaline were investigated in the mouse vas deferens after moderate cooling from 37 to 26 or 22 degrees C. A significant increase of the phasic contractions to noradrenaline was observed at 26 or 22 degrees C compared with responses obtained at 37 degrees C (about 12.3 and 35.6% increase at 26 and 22 degrees C, respectively). The secondary noradrenaline-induced sustained contraction was also significantly enhanced after moderate cooling to 26 degrees C. The potentiation of noradrenaline-induced contraction at 26 degrees C remained in a Ca(2+)-free EGTA (1 mM)-containing solution. However, sustained contraction was suppressed after removal of the calcium from the medium at 37 and 26 degrees C. Contraction to caffeine was significantly enhanced at 22 degrees C compared with 37 degrees C. By contrast, barium chloride-induced contraction of the vas deferens was markedly decreased after moderate cooling to 22 degrees C. In the presence of ouabain (0.1 mM), the noradrenaline-induced peak contraction was significantly increased at 37 degrees C. However, potentiation of the noradrenaline response at 22 degrees C was unaffected by the Na+/K+ pump inhibitor. Noradrenaline-induced peak contractions were depressed in the presence of vanadate (1 mM) and cyclopiazonic acid (10 microM), two Ca(2+)-ATPase inhibitors, at 37 degrees C and also at 22 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

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 BEA strain guinea pigs. In the Dunkin-Hartley strain, sensitization did not signficantly 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 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 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.