SPECIFIC BINDING OF PROSTAGLANDIN F-2-ALPHA TO MEMBRANES OF RAT CORPORA-LUTEA

Prostaglandin F2α (PGF2α) binds specifically to a partially purified membrane preparation from rat corpora lutea. The high affinity, low capacity binding component has a Kd = 4.7 nM and has a capacity of 0.38 pmol/mg protein. Binding kinetics were temperature-dependent with an association rate constant of 2.5 × 105 1/mole-sec and a dissociation rate constant of 4.3 × 10-4 sec-1 at 22°C. Little competition for binding was shown by other prostaglandins and prostaglandin metabolites; the PGF2α analogue ICI 81008 (16-m-trifluoromethylphenyl-prostaglandin F2α) showed a binding affinity similar to that of PGF2α. The specific binding of PGF2α to luteal cell membranes was confirmed by electron microscopy using a ferritin-PGF2α conjugate. Ferritin-PGF2α, was found predominantly on luteal cell surfaces; little binding occurred on other types of cells present. These data demonstrate specific binding of PGF2α to rat luteal membranes. It is suggested that the luteolytic action of PGF2α in the rat may be receptor-mediated. © 1979.