Fig. 7. Roscovitine reduces the fraction of Rac associated with secretory granules and the plasma membrane. (A) Proportional aliquots of the crude nuclear (P1), secretory granule/plasma membrane enriched (P2), microsomal (P3) and cytosol (SN) fractions of cultured pituitary cells treated or not with roscovitine (+ or -Ros) were analyzed by immunoblotting for Rac (top) and actin (bottom); similar results were observed in three experiments. (B) Cultured anterior pituitary cells were either treated with roscovitine (+Ros) or not (-Ros), fixed and stained with a Rac antibody and an ACTH antibody. Arrowheads indicate Rac staining under the plasma membrane; bars, 5 µm.