Fig. 5. The computer modeling of data shown in Fig. 4 on the reduction of respiration rate of mitochondria in situ in permeabilized cardiac cells dependent on endogenous ADP (in the presence of 2mmoll^-1 MgATP) by increasing pyruvate kinase (PK) activity for two different systems. V., respiration rate under given conditions; respiration rate before addition of ATP; _ATP, respiration rate in the presence of 2mmoll^-1 ATP. Solid line: diffusion constant of ADP was taken as D_{0 (}characteristic for Brownian movement in water phase). Broken line: apparent diffusion coefficient was changed to fit the experimental data (separate points show the mean values ± S.D. of respiration rate for given pyruvate kinase activity). Good correlation between simulations and the measurements was obtained for DF=10^-1.8.