Biology of Reproduction, Vol 21, 973-977, Copyright © 1979 by Society for the Study of Reproduction

The Porcine Ovarian Follicle. V. Binding of Concanavalin A to Granulosa Cells during Follicle Maturation

¹ Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota 55455 and Department of Molecular Medicine, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901

The binding of [¹²⁵I]-Concanavalin A ([¹²⁵I]-Con A) to the cell surface has been studied in porcine granulosa cells during ovarian follicular maturation. Total binding amounted to 26-32% of total radioactivity using 2 x 10⁶ cells from large follicles. Nonspecific binding was only 5-12% of total binding. Binding was inhibited by -methyl-D-mannoside and unlabeled Con A. The bound [¹²⁵I]-Con A was readily displaced by -methyl-D-mannoside. Prior binding of hCG to granulosa cells had no effect on [¹²⁵I]-Con A binding. Conversely, binding of Con A to cells also failed to inhibit subsequent [¹²⁵I]-hCG binding. The [¹²⁵I]-Con A binding capacity of granulosa cells was investigated at different stages of follicular development. Scatchard plots of the binding data indicated that the number of Con A binding sites increased 2-3-fold in cells from large follicles compared with cells from medium and small follicles. The binding sites/granulosa cell were 4.0 x 10⁶ for small, 3.9 x 10⁶ for medium and 10 x 10⁶ for large follicle cells. There was no evidence of change in binding affinity. The dissociation constants averaged 1.2 x 10^-7 M for all cells. The increase in Con A binding sites on the surface of large follicle cells temporally correlated with the appearance of microvilli during granulosa cell differentiation.