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

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Abstract
The binding of [125I]-Concanavalin [Con] A to the cell surface was studied in porcine granulosa cells during ovarian follicular maturation. Total binding amounted to 26-32% of total radioactivity using 2 .times. 106 cells from large follicles. Nonspecific binding was only 5-12% of total binding. Binding was inhibited by .alpha.-methyl-D-mannoside and unlabeled Con A. The bound [125I]-Con A was readily displaced by .alpha.-methyl-D-mannoside. Prior binding of hCG [human chorionic gonadotropin] 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- to 3-fold in cells from large follicles compared with cells from medium and small follicles. The binding sites/granulosa cell were 4.0 .times. 106 for small, 3.9 .times. 106 for medium and 10 .times. 106 for large follicle cells. There was no evidence of change in binding affinity. The Kd averaged 1.2 .times. 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.