selective for other prostaglandin receptor subtypes were weak competitors. (fig 8a, 8b, 8c).The pharmacology of the[3H]PGF2- labelled high affinity receptor sites in the BCLM clearly indicates the identification of an FP receptor binding site. Pharmacological eveidence for this conclusion is that traditional prototypic FP- selective prostaglandins such as fluprostenol, Latanoprost acid, cloprostenol and 17 – phenyl-PGF2, were potent competitors of specific [3H]PGF2 binding to the washed BCLM homogenates exhibiting nanomolar affinities, although prostaglandins selective for (DP) BWA868C, (DP) ZK-118182, (EP) enprostil, (EP) sulprostone, (IP) PGI2 and (TP) U46619 all had micromolar affinities. Emulsion autographic studies found a lower level of [3H]PGE2-labelled sites than those labelled by [3H]PGF2 in the BCLM sections.(Fig 6) Figure. 6 Autoradiographic localization of FP receptors in BCLM sections. The top figure depicts total binding of [3H]PGF2 and the lower figure depicts nonspecific binding of [3H]PGF2 defined in the presence of 100 M unlabeled fluprostenol. Similar degree of non-specific binding was obtained when 1-100 M unlabeled fluprostenol or PGF2 were used. Note the high specific binding and high density of [3H]PGF2 binding sites associated with the granulosa cells but the very low density on connective tissue and blood vessels. CT, Connective tissue; GC, granulosa cells; BV, blood vessel. Magnification, 4 of original. Figure. 7 Scatchard plots of specific [3H]PGE1 (a), [3H]PGE2 (b) and [3H]PGF2 (c) binding to BCLM membranes. The plots shown for [3H]PGE1 and [3H]PGE2 are from one representative experiment, while the data for [3H]PGF2 are from 11 experiments; the mean S.E.M. of the Kd and Bmax data from 3 to 11 experiments are also shown for these radioligands. Figure. 8 Competition curves for various PGs displacing specific [3H]PGE2 (a and b) binding and correlation of pharmacology ...
