OBJECTIVETo observe the effect of repeated esophageal acid infusion on specific airway resistance (sRaw) and airway reactivity in the guinea pigs and explore the mechanism.

METHODSsRaw and airway reactivity were measured by double-chamber plethysmography in normal control group (group N), saline control group (group NS), and repeated acid irrigation group (group H). The initial measurement was used as the baseline sRaw and airway reactivity (1d1), and 2 h after the initial measurement, sRaw and airway reactivity were measured again (1d2). Similarly, such measurements were repeated on the 15th day for all the guinea pigs (15d1, 15d2) with a 2-h interval. The content of Substance P (SP) and vasoactive intestinal peptide (VIP) in lung tissue, trachea, BALF and ganglion were detected by ELISA.

RESULTSThe percent change of sRaw, (15d2-1d1)/1d1 in group H was significantly higher than that in group N. The differences in the airway reactivity of the group N, group NS, and group H were not statistically significant. The SP content in the lung, trachea, ganglion and bronchoalveolar lavage fluid (BALF) in group H was significantly higher than those in group N. The SP content in ganglion showed a significant positive correlation to that in the trachea. No significant differences were found in the VIP content in the lung, trachea, ganglion or BALF between the groups.

CONCLUSIONRepeated esophageal acid infusion increases the airway resistance, but not the airway reactivity in normal guinea pigs. SP may be involved in development of high sRaw through the esophageal-tracheobronchial reflex.