Prostanoid receptors involved in the relaxation of human bronchial preparations

Abstract

1. Iloprost and cicaprost (IP-receptor agonists) induced relaxations in the histamine- (50 μM) contracted human bronchial preparations (pD2 values, 6.63 ± 0.12 and 6.86 ± 0.08; E(max) values, 90 ± 04 and 65 ± 08% of the papaverine response for iloprost (n = 6) and cicaprost (n = 3), respectively). 2. Prostaglandin E2 (PGE2) and misoprostol (EP-receptor agonist) relaxed the histamine-contracted human bronchial preparations (pD2 values, 7.13 ± 0.07 and 6.33 ± 0.28; E(max) values, 67 ± 04 and 57 ± 98% of the papaverine response for PGE2 (n = 14) and misoprostol (n = 4), respectively). In addition, both relaxations were inhibited by AH6809 (DP/EP1/EP2-receptor antagonist; 3 μm; n = 5-6). 3. The PGE2-induced relaxations of human bronchial preparations were not modified by treatment with AH23848B (TP/EP4-receptor antagonist; 30 μM; n = 4). 4. The contracted human bronchial preparations were significantly relaxed by prostaglandin D2 (PGD2) or by BW245C a DP-receptor agonist. However, these responses did not exceed 40% of the relaxation induced by papaverine. In addition, the relaxations induced by PGD2 were significantly inhibited by treatment with a DP-receptor antagonist BWA868C (0.1 μM; n = 3). 5. These data suggest that the relaxation of human isolated bronchial preparations induced by prostanoids involved IP-, EP2- and to a lesser extent DP-receptors but not EP4-receptor.