Figure 3.

Time course of rundown of permeabilized mast cells in the presence and absence of recombinant Rac2. The cells were permeabilized with SL-O in a buffer (pH 6.8) containing Mg·ATP (1 mM) and sufficient EGTA (0.1 mM) to suppress Ca²⁺ to below pCa8, and in the presence and absence of Rac2 (14.8 μg ml⁻¹). At various times (indicated), samples were removed and stimulated by transfer to solutions containing Ca·EGTA (3 mM) to regulate pCa5 plus GTPγS (100 μM). After a further 20-min incubation, the cells were sedimented by centrifugation, and the supernatants were sampled for analysis of secreted hexosaminidase. ○ and •, Cells stimulated with Ca²⁺ (pCa5) and GTPγS (100 μM); □ and ▪, unstimulated cells; filled symbols indicate presence of Rac2. Similar results were obtained on three occasions.