Prostaglandin E 2 receptor in the myometrium: Distribution in subcellular fractions

Abstract

[ 3H]Prostaglandin (PG) E 2 bound specifically to several subcellular fractions from bovine myometrium. The binding was temperature dependent, rapid, and reversible. PGE 2 and PGE 1 competed for the [ 3H]PGE 2 binding site. The PGs inhibited in the following decreasing order: PGE 2 = PGE 1 ⪢ PGF 2α > PGA 2 > PGF 1β > PGB 2. No competitive effect could be found for oxytocin. Scatchard analysis of the binding data were interpreted as showing a single high-affinity binding constant. There was no difference in the binding constant between the various fractions. The average molar dissociation constant was 2.74 ± 0.14 × 10 −9. Quantitative differences in the maximum number of binding sites were observed between fractions. One plasma membrane fraction contained 21.4 ± 2.3 × 10 −11 and the sarcoplasmic reticulum contained 11.2 ± 0.8 × 10 −11 mol binding sites/g. The results suggest that there is a high-affinity PGE 2 receptor present in both plasma membrane and sarcoplasmic reticulum.