Fig. 5. Distribution of ER in density gradient fractions in relation to IRP1 immunoreactivity. This graph shows the distribution of IRP1 and ER immunoreactivity in control rat livers. The primary y-axis shows the IRP1 and ER distribution in the density gradient fractions. The secondary y-axis shows the ER marker, cytochrome C-NADPH reductase, which was used to plot the distribution of ER in fractions obtained from density gradient centrifugation. The fraction number is shown on the x-axis. Enzyme activity in each fraction is plotted as a function of total protein. 5 µg of each fraction was subjected to western blot analysis to determine IRP1 immunoreactivity. These data confirm the localization of IRP1 immunoreactivity in ER containing fractions. These experiments were performed in duplicate and representative data are shown.