External NADPH oxidation with DcQ as electron acceptor. NADPH dehydrogenase activities in the presence of Ca2+ and antimycin A are presented as percentage of control in each experiment. No activity was seen without Ca2+ added to the reaction. Error bars indicate standard deviation (n = 2). Control activities were 315 and 479 nmol NADPH min-1 mg-1 in the two experiments. Samples are denoted as for Fig. 1.