[Metabolic effects of orotic acid].

Orotic acid is an important representative of the pyrimidines, the pathophysiological importance of which is less well-known in comparison to the purines. Increases of the excretion of orotic acid in the urine are found e.g. in enzyme defects of the urea cycle, of the orotate phosphoribosyl transferase or the orotidin-5'-monophosphate decarboxylase. Numerous enzymatic systems of the liver are influenced by supply of orotic acid. Toxic influences on the liver may be reduced by orotic acid. In rats orotic acid induces a fatty degeneration of the liver by disturbances of the secretion of lipoproteids. The oxidation of fatty acid by hepatic mitochondria is also reduced by orotic acid. In the blood a decrease of the serum lipid concentrations develops. The effect of the orotic acid in combination with clofibrinic acid was controlled in the double-blind test in patients with hyperlipoproteinaemias. In patients with hyperlipoproteinaemia type V a drastic decrease of the serum lipid concentrations developed and the chylomicrons disappeared from the fasting serum.