Distribution of two mitochondrial populations in rabbit kidney cortex and medulla

Abstract

Mitochondria from rabbit kidney were separated by isopycnic density centrifugation into two distinct bands with mean densities of 1.178 (M 1) and 1.163 (M 2). Cortex and medulla of rabbit kidney, separated surgically, yielded both the M 1 and M 2 population of mitochondria but in markedly different proportions. From whole kidney, M 1 fraction contained 70 to 75% of the total mitochondrial protein isolated, whereas from cortex, M 1 was 83–95% and from medulla 15 to 37% of the total mitochondrial protein. The rate of incorporation in vivo of 3H-leucine into mitochondrial proteins from normal and renoprival kidneys indicated differences between the M 1 population and the M 2 population of the cortex and medulla. The results suggest that both the cortex and medulla of the kidney contain two distinct mitochondrial populations.