Fig. 8.

Lack of cyclosporin A effects on levels of PC12 receptors binding αBgt. PC12-C cells in culture were treated either with vehicle (Control), tunicamycin (1 μg/ml), or cyclosporin A (10 μm) for 24 hr and then assayed either for αBgt binding in RIAs with mAb 318 (which recognizes the chick but not rat α7 gene product) to immunotether receptors (Total Sites) or for αBgt-binding to intact cells in culture (Surface Sites). Values represent the mean ± SEM of three or four separate experiments and are expressed as percentages of those obtained from control cells. Tunicamycin treatment caused a large reduction in αBgt binding, indicating that receptors both on the cell surface and inside were normally turning over. Cyclosporin A treatment had little effect either on the total number of αBgt-binding receptors assayed or on those present on the cell surface.