G. Baersch et Jc. Frolich, A NEW BIOASSAY TO STUDY CONTRACTILE AND RELAXANT EFFECTS OF PGE(2) ONPERFUSED GUINEA-PIG TRACHEA, Journal of pharmacological and toxicological methods, 36(2), 1996, pp. 63-68
The aim of this study was to investigate the effects of PGE(2) under d
ifferent experimental conditions. By a newly developed imaging bioassa
y system, changes of the diameter of isolated perfused guinea-pig trac
heal tubes were continuously measured. The results were compared with
those of a conventional ring bioassay system. The effect of PGE(2) was
examined in epithelium-intact and -denuded tubes. The potency of PGE(
2) applied to the inner surface of tube preparations was significantly
enhanced by about six-fold in epithelium-denuded compared with epithe
lium-intact tubes. In rings there was no difference. The results sugge
st a potential role of epithelium in assessment of airway reactivity i
n vivo. The study demonstrates, that the effects of PGE(2) depend crit
ically on the experimental approach. PGE(2) (0.01 nmol 1(-1)-1 mu mol
1(-1)) contracted tracheal tubes, but resulted in relaxation of ring p
reparations under basal tone. The spontaneous tone of guinea pig trach
ea can be reduced with the cyclooxygenase inhibitor diclofenac. Pretre
atment of the rings with diclofenac reversed the relaxation into contr
action. Preincubation of tube preparations with diclofenac had no effe
ct on basal tone, indicating that there was no inherent spontaneous pr
ostanoid-dependent tone or the mediators may be washed out at a relati
vely fast rate and, therefore, tone may not be apparent. (C) 1996 Else
vier Science Inc.