Ultrastructural effects of riboflavin deficiency on rat hepatic mitochondria.

The hepatic mitochondria of rats fed a riboflavin-deficient diet were examined by electron microscopy. Discoidal mitochondria with elongated cristae increased in frequency from day 4 to day 12 of the test diet. At day 22, sheaves of closely packed cristae were present in many otherwise typical mitochondria. At day 53, numerous cupshaped mitochondria appeared; these often nested one inside the other. From this day onward, the mitochondria showed a tendency towards increasing size. By day 82, some had a diameter greater than 8 micrometer. These and other, smaller mitochondria often contained extremely prominent matrix granules. The production by riboflavin-deficiency of giant mitochondria in the rat liver appears to be unrelated to their capacity to carry out oxidative metabolism.