Gel filtration and sedimentation behaviour of receptor-gonadotrophin complexes from rat ovary

Membrane particles of luteinized rat ovaries and immature granulosa cells of rat ovarian follicles were labelled with [125I]human chorionic gonadotrophin (hCG), membranes of mature granulosa cells were also labelled with [125I]ovine follitropin (oFSH). Hormone-receptor complexes were solubilized with Triton X-100 and their physical properties were characterized by sedimentation and gel filtration. No difference in the macroscopic physical properties of the specific receptor-hCG-complex was observed between different developmental stages of granulosa cells. The Strokes radius of the specific receptor-[125I]hCG-complex was 58 A and the sedimentation coefficient 6.7 +/- 0.3 S. The physical properties of free LH/hCG-receptor of luteinized ovaries were also characterized. The Strokes radius was found to be 57-59 A and the sedimentation coefficient 4.8-5.6 S. Both [125I]hCG and [125I]oFSH formed non-specific complexes with ovarian as well as with non-gonadal membrane components. The sedimentation coefficient of the non-specific complex was 1.3 +/- 0.5 S and the Strokes radius 49 A. These results show that the macroscopic physical properties of the receptor-hCG-complex do not change during the maturation and subsequent luteinization of the granulosa cells. The methods used were not enough discriminating to reveal the existing structural differences between receptor-oFSH-complex and receptor-hCG-complex.