Characterization of prostanoid receptors mediating inhibition of histamine release from anti-IgE-activated rat peritoneal mast cells

1 Prostanoid receptors mediating inhibition of anti-IgE induced histamine release from rat peritoneal mast cells have been characterized pharmacologically. PGD(2) and the specific DP receptor agonists BW 245C and ZK 118182 were the most potent inhibitors with half-maximal concentrations of 0.26, 0.06 and 0.02 mu M respectively. The maximum inhibition attainable was 60-65% with 10(-5) M BW 245C and ZK 118182. 2 Among several EP receptor agonists investigated, only PGE(2) and the EP2/EP3 receptor agonist misoprostol induced significant inhibition (46.8+/-4.7% at 10(-4) M and 18.7+/-6.8% at 10(-5) M respectively). The IP receptor agonists cicaprost and iloprost were both less potent than the DP agonists in inhibiting histamine release (45.2+/-3.3% and 35.1+/-2.5% inhibition respectively at 10(-5) M), whereas PGF(2 alpha) and the TP receptor agonist U-46619 were only marginally effective. 3 The EP4/TP receptor antagonist AH 23848 failed to affect the inhibitory actions of PGD(2) or PGE(2) even at 10(-5) M, whereas the DP/EP1/EP2 receptor antagonist AH 6809 slightly enhanced the effect of PGD(2) at 10(-6) M. 4 At concentrations of 3 x 10(-6) to 10(-5) M, the putative DP receptor antagonist ZK 138357 dose-dependently suppressed the inhibitory activities of the DP agonists, PGE(2) and cicaprost. The antagonism of ZK 138357 against the DP receptor agonists appeared to be competitive with pA(2) values of around six. 5 In conclusion, these data support our earlier proposal that an inhibitory DP receptor is the predominant prostanoid receptor in rat peritoneal mast cell. The properties of this receptor in relation to putative DP receptor subtypes reported in the literature are discussed.