Fig. 2. (A) Allometric plot of the proton leak (at 170 mV and 37°C) in isolated liver mitochondria from mammal species differing in body mass (data are from table 1 in Porter et al., 1996). (B) Allometric plot of the activity of the Na⁺ pump (at 37°C and expressed as K⁺ uptake rate) in liver and kidney tissue slices from mammal species differing in body size. (Data from Couture and Hulbert, 1995a.) Values are means ± S.E.M. The respective allometric equations are shown in each figure.