Lambooy (1961) has shown that, while several analogues of riboflavin are able to replace the vitamins in the metabolism of some microorganism, 7-ethyl-8-methyl flavin is able to serve as the sole flavin in the metabolism of the rat. This flavin is abl...
Lambooy (1961) has shown that, while several analogues of riboflavin are able to replace the vitamins in the metabolism of some microorganism, 7-ethyl-8-methyl flavin is able to serve as the sole flavin in the metabolism of the rat. This flavin is able to serve as a completely adequate replacement for riboflavin in the metabolism of Wistar (Lambooy, 1961) and Sprague-Dawley rats (Yoon S. Kim et al, 1966) in terms of growth, survival, optimal physical appearance, and efficient utilization of food. Administration of 7-ethyl-8-methyl flavin to weanling rats as their only source of flavin permits a normal growth with a concomitant rapid and extensive loss of succinic dehydrogenase activity (SDH) from the liver, heart and kidney to within 24, 48, and 67% of the normal level, respectively, on day 42 following initiation of a 7-ethyl-8-methyl flavin diet. This result was essentially identical with that previously reported (Y.S. Kim and Lambooy, 1967). The purpose of the experiments described here is to study whether the decreased SDH activity in the tissue of rats is related to the metabolism of glucose and de novo biosynthesis of lipid from glucose in the liver of rats when D-glucose-^(14)C(U) is administered intraperitoneally to the rat maintaining SDH activity from liver, heart and kidney at 24, 48 and 67% of the normal level. This is also to study whether the total triglyceride and the total lipid content in the liver of rats is influenced by the loss of SDH activity in the liver of rats which have received 7-ethyl8-methyl flavin. The present study shows that there wa.s no significant difference in the total amount of ^(14)CO₂ expired from D-glucose-^(14)C(U) through the respiration of rats which had received 7-ethyl-8-methyl flavin compared to control rats which received riboflavin, indicating that the metabolic rate of glucose in the tissues of rat receiving 7-ethyl-8-methyl flavin is similar to that of the control rats. However, compared to the control level only 50% of ^(14)C total lipids were incorporated by de novo biosynthesis from D-glucose-^(14)C(U) in the liver of rats receiving 7-ethyl-8-methyl flavin but the total content of triglyceride and total lipids in the liver of rats receiving 7-ethyl-8-methyl flavin were increased by 29 and 30% over the normal level. This may be due to the increased of lipid transport from the peripheral adipose tissue due to the decreased SDH activity in the liver of rats.