Endocrinology, Vol 109, 1399-1403, Copyright © 1981 by Endocrine Society

ARTICLES

Antibodies to purified luteinizing hormone receptor localize the receptor at the luteal cell surface

K Metsikko and H Rajaniemi

Antiserum to purified LH (hCG) receptor was raised in rabbits and used to localize the receptor with the peroxidase-antiperoxidase complex method in pseudopregnant rat ovary. The receptor was purified using immobilized antibodies to hCG as an immunoaffinity using immobilized antibodies to hCG as an immunoaffinity matrix for solubilized receptor- hCG complex. The unoccupied receptor was eluted from the column by acetic acid and used to immunize rabbits. The antibodies produced inhibited binding of [125I]iodo-hCG to pseudopregnant rat ovarian particles in a dose-dependent manner, mainly by reducing the number of available binding sites. The antireceptor serum gave a positive peroxidase staining at the luteal cell periphery on ovarian sections bearing unoccupied receptors, while no staining was seen on spleen, kidney, or liver sections. No reaction was seen on ovarian sections when the receptors were saturated with hCG in vivo, while the anti-hCG serum gave a distinct peripheral reaction in luteal cells on these sections. This fact and the idea that the antibodies produced did not bind to purified receptor-[125I]iodo-hCG complex suggest that the hormone-binding site and the antibody-binding site on the receptor are very near each other or identical. The immunocytochemical findings suggest that the majority of the LH (hCG) receptors in luteal cells are located at the cell surface.