Riboflavin and Mouse Hepatic Cell Structure and Function

Abstract

Mice which had been on a riboflavin-free diet for 6-8 wk were given daily intraperitoneal injections of riboflavin . The hepatic mitochondria, which in the deficient animals were greatly enlarged, were restored to normal dimensions within 3 days . Normalization of the mitochondrial population was brought about by division of the giant organelles . Dividing mitochondria were characterized by a membranous partition separating the inner compartment into two distinct chambers . Such organelles showed varying degrees of pinching at the level of the partition . The most common site of partition formation was at the base of a small mitochondrial bud . During the 1st day of recovery, dividing mitochondria were so common that they could be easily found in mitochondrial pellets . Injection of riboflavin into normally nourished mice also produced an apparent increase in the frequency of dividing mitochondria in the liver cells .

Effects of riboflavin deficiency on the lipids of rat liver mitochondria and microsomes.

“…In addition to the decline in rate of respiration , changes of intracellular microstructure of the livers were revealed in the riboflavin deficient rats (1) or mice (2)(3). It was reported in our earlier paper that riboflavin deficiency exerted effects upon fatty acid composition of rat liver lipids and decrease in arachidonic acid and increase in linoleic acid were observed (4).…”

“…Weanling rats were fed a riboflavin-deficient diet for 5 weeks, and enlargement of the liver mitochondria, diminution of the inner membrane profiles and discontinuity of the outer membrane were revealed by electron microscopy as reported previously by others (1)(2)(3). Fatty acid composition of the liver mitochondria was remarkably altered and incorporation of 32P into the respective subspecies of phosphatidylcholine of the mitochondria was variably changed by the deficiency, whereas the content of phospholipids in the mitochondria was slightly altered.…”

Mitochondrial division in rat cardiomyocytes: An electron microscope study

“…Mitochondria of such appearance were originally described in hepatocytes more than half a century ago (Fawcett, 1955), but it could not be decided whether this morphology was consistent with division or fusion or both. The direction of this process was not made clear until the publication of a study of recovering giant mitochondria (Tandler et al, 1969). In this experiment, hepatic mitochondria that had achieved giant size (larger than the hepatocyte nuclei) due to dietary riboflavin deficiency (Tandler et al, 1968) were administered the missing vitamin.…”

“…The direction of this process was not made clear until the publication of a study of recovering giant mitochondria (Tandler et al, 1969). In this experiment, hepatic mitochondria that had achieved giant size (larger than the hepatocyte nuclei) due to dietary riboflavin deficiency (Tandler et al, 1968) were administered the missing vitamin. The megamitochondria quickly were restored to normal size (within 48 hours) by forming buds with a partition at their base, followed by ingrowth of the outer membrane into the said partition.…”

Megamitochondria in the serous acinar cells of the submandibular gland of the neotropical fruit bat, Artibeus obscurus

“…1); such enlarged organelles were not detected in the other seven species of Artibeus that we examined. Unlike the situation in hepatocytes of mice on a riboflavin-deficient diet where giant mitochondria appear as lucent cytoplasmic bodies (Tandler et al, 1968), or in seromucous cells of the submandibular gland of the long-haired fruit bat (Tandler and Phillips, 1993) where enlarged mitochondria appear as densely stained spheres, the megamitochondria in the Artibeus cells in semithin sections stain precisely at the density and hue of the surrounding cytosol and therefore are discernible only with the greatest difficulty; it requires electron microscopic examination to ascertain their presence at this site.…”