Effect of carvacrol on tracheal responsiveness, inflammatory mediators, total and differential WBC count in blood of sensitized guinea pigs.

The effects of carvacrol on tracheal responsiveness (TR) to methacholine and ovalbumin (OA), serum nitric oxide (NO) concentration, total and differential white blood cells (WBC) in blood of sensitized guinea pigs were examined. Five groups of guinea pigs sensitized to OA were given drinking water alone (group S), drinking water containing three concentrations of carvacrol (40, 80 and 160 µg/mL) and dexamethasone (50 µg/mL). TR to methacholine and OA, serum NO concentration, total and differential WBC in blood of sensitized and control guinea pigs were measured (n = 6, for each group). TR to methacholine and OA, serum level of NO and nitrite, total WBC, eosinophil and neutrophil counts were increased but lymphocyte decreased in group S compared with control group (P < 0.01 for NO and nitrite and P < 0.001 for other cases). Treatment of S animals with dexamethasone and two higher concentrations of carvacrol significantly improved all measured parameters except TR to OA in treated group with dexamethasone (P < 0.05 to P < 0.001). Treatment of S animals with low concentration of carvacrol also improved TR to methacholine and OA, total WBC count and nitrite level (P < 0.05 to P < 0.001). The effects of two higher concentrations of carvacrol on TR, NO and nitrite and the effects of its highest concentration on total and differential WBC count were significantly higher than those of dexamethasone (P < 0.05 to P < 0.001). In addition, the effects of highest concentration of carvacrol on all parameters and its medium concentration on some parameters were significantly higher than its low concentration (P < 0.05 to P < 0.001). These results showed a preventive effect of carvacrol on tracheal responsiveness, serum level of NO and nitrite, total and differential WBC in the blood of sensitized guinea pigs which was equal or even more potent than dexamethasone at used concentrations.