Fish oil rich in w3 fatty acids is reported to have beneficial effects in human asthma by decreasing bronchial reactivity (BR) and pulmonary oxidative stress. The aim of this study was to asses the effect of a 3 week fish oil complementation in 6 cats that were sensitised with Ascaris suum (AS). Cats were divided in 2 groups receiving for 3 weeks w3 fish oil or a placebo (PL). Treatments were inverted after a wash-out period. Efficiency of complementation was assessed by determination of w6:w3 fatty acid ratio in red blood cells (RBC). BR was determined after w3 or PL complementation 48 h before (Pre-AS) and 48 h (Post-AS) after AS-challenge using barometric whole body plethysmography (BWBP) and carbachol nebulisations allowing calculation of the concentration inducing a 300% increase of Penh (C-Penh300%). Bronchoalveloar lavage fluid (BALF) was sampled for determination of BALF cytology and 8-iso-PGF2alpha (IsoP).

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	w6:w3 RBC	Pre-AS C-Penh300%	Post-AS C-Penh300%	BALF IsoP(pg/ml)
W3	6.6±0.8	0.039±0.016	0.027±0.008	49±36
PL	4.1±0.4*	0.030±0.008	0.023±0.007*†	92±54*

Post-AS challenge BALF cytology was similar between groups. Changes in RBC w6:w3 ratio showed that w3 fatty acids were efficiently absorbed. A treatment-related difference of Post-AS C-Penh300% was detected, suggesting that w3 complementation modulated AS-induced BR. Although BALF cytology remained unaffected by w3 complementation, the decrease of BALF IsoP indicated diminished pulmonary oxidative stress.