We report a 3-year-old Saudi boy with recurrent episodes of vomiting, poor feeding, and altered mental status accompanied by an intermittent mild hyperammonemia, and a large elevation of urinary orotic acid. Sanger sequencing of the ornithine transcarbamylase (OTC) gene revealed a novel hemizygous deletion at the fourth nucleotide of intron 4 (c.386+4delT) in the proband and his asymptomatic mo...

Mice with the X-chromosomal sparse-fur (spf) mutation frequently have urinary bladder stones composed mostly of orotic acid, which was identified by the following criteria: ultraviolet and infrared absorption, spectra, chromatographic behavior, melting point, and reactivity in a specific color test. This clue led to the discovery that spf-bearing mice have an abnormal form of liver ornithine ca...

The turnover of messenger RNA (mRNA) in two intrahepatically transplantable hepatomas (5123 and 19) and host livers of Buffalo rats was evaluated with four different approaches. [14C]Oroticacid incorporation into the rapidly labeled peak between 18S and 4S of total polyribosomal RNA was measured, in vitro RNase assay of [14C]orotic acid-labeled mRNA of polyribosomes was utilized. The decay of m...

Orotic acid and its salts chronically administered have been shown to significantly improve cardiac function in pathological settings associated with ischemia-reperfusion (I/R) injury. The aim of our study was to investigate the effect of magnesium orotate (Mg-Or) administration at the onset of post-ischemic reperfusion on myocardial function and infarct size (IS). Ex-vivo experiments performed...

Uniformly fatty livers from orotic acid-fed rats secreted almost no very low density lipoproteins (VLDL) but normal amounts of nascent high density lipoproteins (HDL) accumulated in perfusates. When lecithin:cholesterol acyltransferase (LCAT) was inhibited, nascent HDL were uniformly discoidal and lacked cholesteryl esters. Lipid and apoprotein compositions of nascent HDL from normal and fatty ...

In skeletal muscle we evaluated both the aspartateamino-transferase and cytochrome-oxidase activity and incorporation of 14 C-leucine into proteins of myofibrils and sarcoplasm. (14C-leucine in a dose of 140 ci/kg. of body weight was injected intraperitoneally 30 min. prior to evaluation). The content of 4 C-orotic acid in skeletal muscle RNA was then determined similarly in 30 min. subsequent ...

Investigations of the mechanism of pyrimidine nucleotide formation from orotic acid led to the isolation and characterization of an activated ribose phosphate derivative which serves as an intermediate in the overall process. In earlier communications (1) we have described briefly the enzymatic synthesis of this new intermediate, identified as PRPPI (equation (I)), and the occurrence of enzymes...