Fig. 3. Effect of the calcium ionophore A23187 on the sulfation of ricin sulf-2. MDCK II cells were incubated with radioactive sulfate for 3 hours at 37°C, and 10 µM A23187 was added for the last 30 minutes. Then ricin sulf-2 (200 ng/ml) was added to the medium, and the incubation was continued for 2 hours. The cells were subsequently washed with 0.1 M lactose, lysed and immunoprecipitated with rabbit anti-ricin antibodies. The adsorbed material was analyzed by SDS-PAGE (12%) before autoradiography.