Na. Sharif et al., Pharmacology and autoradiography of human DP prostanoid receptors using [H-3]-BWA868C, a DP receptor-selective antagonist radioligand, BR J PHARM, 131(6), 2000, pp. 1025-1038
1 A potent and highly selective DP prostanoid receptor antagonist radioliga
nd, [H-3]-cyclohexyl-N-BWA868C (3-benzyl-5-(6-carboxyhexyl)-1-(2-cyclohexyl
-2-hydroxyethyl-amino) hydantoin, ([H-3]-BWA868C)), has been generated for
receptor binding and autoradiographic studies.
2 Specific [H-3]-BWA868C binding to human platelet membranes achieved equil
ibrium within 60 min at 23 degreesC and constituted up to 95% of the total
binding. The association (K (+ 1)) and dissociation (K (- 1)) rate constant
s of binding were 0.758/-0.064 min(-1), mmol and 0.0042+/-0.0002 min(-1), r
espectively, yielding dissociation constants (K(D)s) of 5.66+/-0.44 nM (n =
4).
3 Specific [H-3]-BWA868C bound to DP receptors with a high affinity (K-D =
1.45+/-0.01 nM, n = 3) and to a finite, saturable number of binding sites (
B-max = 21.1 +/- 0.6 nmol g(-1) wet weight).
4 DP receptor class prostanoids (e.g. ZK118182, BW245C, BWA868C, PGD,) exhi
bited high (nanomolar) affinities for [H-3]-BWA866C binding, while prostano
ids selective for EP, FP, IP and TP receptors showed a low (micromolar) aff
inity.
5 Specific DP receptor binding sites were autoradiographically localized on
the ciliary epithelium/ process, longitudinal and circular ciliary muscles
, retinal choroid and iris in human eye sections using [(3H)]-BWA868C. Whil
e [H-3]-PGD(2) yielded similar quantitative distribution of DP receptors as
[H-3]-BWA868C, the level of non-specific binding observed with [H-3]-PGD(2
) was significantly greater than that observed with [H-3]-BWA868C.
6 Tt is concluded that [H-3]-BWA868C is a high-affinity and very specific D
P receptor radioligand capable of selectively labelling the DP receptor. [H
-3]-BWA868C may prove useful for future homogenate-based and autoradiograph
ic studies on the DP receptor.