FOOD RESTRICTION-MEDIATED ADRENAL INFLUENCES ON ANTIGEN-INDUCED BRONCHOCONSTRICTION AND AIRWAY EOSINOPHIL INFLUX IN THE GUINEA-PIG

The aim of this study was to measure the effects of food restriction o n antigen-induced bronchoconstriction and inflammatory cell influx in guinea pigs and to determine the role of plasma cortisol and catechola mine concentrations. Ovalbumin (OA; 0.3 mg/kg, i.v.) was administered to OA-sensitized, anesthetized guinea pigs which had been allowed free access to food or had been food restricted for 18 h prior to OA chall enge. In addition to higher plasma levels of epinephrine (30% increase ) and cortisol (33% increase), fasted guinea pigs had significantly lo wer (60% decreased) maximal bronchoconstrictor responses to GA than no nfasted, sensitized litter mates. Additionally, groups of fasted or fe d animals were subdivided into two additional treatment groups: (I) sa line-pretreated or (2) polyethylene glycol 400 (PEG)-pretreated (1 ml/ kg, p.o., 1 h prior to antigen challenge). In saline-treated, fasted a nimals, bronchoconstrictor responses to antigen were significantly dim inished (67% decreased) and epinephrine and cortisol levels were incre ased (64 and 34%, respectively) compared to the corresponding fed grou p. In both fasted and fed groups, the PEG-treated guinea pigs had high er plasma epinephrine and cortisol levels than animals which received saline, but no significant differences were detected within the PEG-tr eated group. Plasma norepinephrine concentrations were lower in all fa sted groups. In a separate model in conscious guinea pigs, there were no differences in aerosol OA-induced bronchoconstriction and eosinophi l influx between fasted and fed groups. However, compared to the salin e pretreatment group, PEG administration reduced the antigen-induced b ronchoconstriction and eosinophilia in both fed and fasted guinea pigs . We speculate that the reduced responsiveness to antigen in fasted ve rsus fed animals may result from food-restriction-induced, stress-rela ted release of epinephrine and cortisol from the adrenal glands, there by suppressing mast cell degranulation or reducing responsiveness to s pasmogenic and chemotactic mediators. In addition, the results suggest that oral dosing with 100% PEG may enhance this phenomenon.