Different immunological sensitizing regimens and airway responsiveness in vitro to contractile agonists in...

Groups of guinea-pigs were sensitized to ovalbumin, using different regimens to induce either IgG-like antibodies or IgE-like and IgG-like antibodies and the responsiveness to histamine and carbachol in vitro of tracheal and lung parenchymal strips was determined. EC50 values for histamine and carbachol in both tracheal and lung parenchymal strips were not significantly different for either group of sensitized guinea-pigs or their respective controls. The maximal tension developed in parenchymal strips was not significantly different for either sensitized or control groups. For tracheal strips, maximal tension was not significantly different in each group except in animals with IgG-like antibodies, which developed less maximal tension with histamine than controls. The absence of any increase in maximal tension or any change in EC50 to histamine or to carbachol in tracheal or parenchymal strips from immunized guinea-pigs indicates that immunological sensitization does not increase the responsiveness of smooth muscle to these contractile agonists.