In vitro allergic bronchoconstriction in the brown Norway rat

The ovalbumin (OA)-sensitized Brown Norway rat (BN) demonstrates early-response (ER) and late-response (LR) allergic bronchoconstriction. To determine whether these responses could be replicated in vitro, we studied lung explants from 8-wk-old male BN rats (wt: 239 +/- 28 g), of which 19 were sensitized to OA (test) and 16 served as controls. Two weeks after sensitization, the animals' lungs were removed, filled with a 1% (wt/vol) agarose-containing solution at 37 degrees C, and cooled to 4 degrees C. Transverse slices (0.5 to 1.0 mm thick) were cut and cultured overnight. Airways were visualized with an inverted microscope and baseline images were obtained with a video camera. To study the ER, 40 airways from 15 test rats and 29 airways from 10 control rats were challenged with 2 micrograms OA and imaged each minute for 10 min. To study the LR, 40 airways from 12 test rats and 44 airways from 12 control rats were challenged with 2 micrograms OA and imaged each hour for 8 h. The maximal response (MR) for each airway was defined as the percent of airway closure. The ER and LR were both defined as an MR > or = mean + 2 SD of the controls. An ER occurred in 38 of 40 test and 2 of 29 control airways (mean MR: 42 +/- 24% versus 4 +/- 3%, p < 0.001), and was completely blocked by methysergide pretreatment in 13 airways.(ABSTRACT TRUNCATED AT 250 WORDS)