Comparison of the Mitochondria of the Small Intestine of Vertebrates

MITOCHONDRIA of the intestinal mucosa of the following vertebrates have been examined by electron microscopy: the rat ( Rattus norvegicus ), guinea pig ( Cavia percellus ), chicken ( Gallus domesticus ), lizard ( Tiliqua rugosa ), toad ( Bufo marinus ) and carp ( Carassius auratus ) (Fig. 1). The mitochondria in the intestinal cells of these species showed no major differences in structure from the other mitochondria that have already been described 1,2 . The intestinal mitochondria from all these species swelled when they were isolated by differential centrifugation in 0.25 M sucrose (Fig. 2), but all except those from the rat exhibited considerable succinoxidase activity as measured manometrically (Table 1). The oxygen uptake of homogenates of the intestinal mucosa of rats was also low and variable compared with that of homogenates of intestinal mucosa prepared from guinea pigs. In contrast, the oxygen uptake (per mgm. dry weight) of whole intestinal cells of both the rat and the guinea pig was similar.