Ultrastructural effects of dietary galactoflavin on mouse hepatocytes

The ultrastructural effects of a galactoflavin-supplemented, riboflavin-free diet were chronologically examined in mouse hepatocytes. The mitochondrial population suffered the greatest changes. Beginning with day 3 of the experimental diet, the mitochondria first became elongated, then later rounded up to become somewhat enlarged spheres. By day 20–22, the mitochondria reached diameters of about 6 μm, and had cristae that were largely confined to the periphery of the organelles. Throughout the course of enlargement, spontaneously partitioned mitochondria of all sizes were common. When mice with advanced ariboflavinosis were injected with riboflavin, mitochondrial recovery took place over a period of more than 10 days. Division of the enlarged mitochondria proceeded by medial attenuation, rather than by partition formation and constriction. The mechanism that selects which of the two modalities of mitochondrial replication will prevail remains undetermined.