Effect of Sodium Hypochlorite on Specific Airway Resistance and Airway Reactivity in Guinea Pigs

Abstract

To evaluate the effect of sodium hypochlorite (NaOCl) on specific airway resistance (SRaw) and the possibility that NaOCl is involved in causing airway hyperreactivity, we studied the effect of exposure to NaOCl aerosol on SRaw and airway reactivity to inhaled histamine aerosol in intact, unanesthetized, spontaneously breathing guinea pigs. A 1-min inhalation of 1.2–10.0% NaOCl caused an increase in SRaw in three of six animals in a concentration-dependent manner. To assess the airway reactivity, the effective concentration of histamine that produced a doubling of baseline SRaw (EC₂₀₀His) was determined. A 5-min inhalation of 3.6% NaOCl aerosol caused an acute decrease in EC₂₀₀His without a corresponding change in SRaw, whereas a 5-min inhalation of normal saline caused no significant changes in SRaw and EC₂₀₀His. Therefore, a 5-min inhalation of 3.6% NaOCl induced airway hyperreactivity. On the contrary, a 15-min inhalation of 3.6% NaOCl did not cause significant changes in mean EC₂₀₀His values at 5 min, 5 hr, and 1 week after exposure. The mean SRaw at 5 hr after a 15-min inhalation of 3.6% NaOCl was higher than that of the baseline value. A 15-min inhalation of normal saline aerosol caused an increase in EC₂₀₀His i.e., reduced airway reactivity, 5 min after exposure. The increased EC₂₀₀His returned to baseline level at 5 hr and 1 week after exposure. A 15-min inhalation of normal saline caused no significant change in SRaw during the study period.

Our study indicates that acute NaOCl aerosol inhalation causes a temporary increase in SRaw and airway hyperreactivity to inhaled histamine in guinea pigs.