QUANTIFICATION OF HISTAMINE IN PLASMA AND PULMONARY FLUIDS FROM HORSES WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE, BEFORE AND AFTER NATURAL(HAY AND STRAW) CHALLENGES

A commercial radioimmunoassay kit was used to quantify histamine conce ntrations of plasma, bronchoalveolar lavage fluid (BALF) and pulmonary epithelial lining fluid (PELF) of normal horses and horses with chron ic obstructive pulmonary disease (COPD), before and after 'natural (ha y and straw) challenge' (NC), There were no significant changes in the concentrations of histamine in plasma or BALF at 0.5 or 5 h after NC, but the PELF histamine concentration of COPD affected horses was sign ificantly increased at 5 h, but not at 0.5 h, following NC. As the his tamine concentrations of whole BALF lysates were significantly correla ted with the numbers of metachromatically staining cells, presumed to be mast cells and/or basophils, these findings support involvement of a late phase, IgE mediated, hypersensitivity reaction in the pathogene sis of equine COPD.