Urinary excretion of orotic acid, orotidine and other pyrimidines in a patient with purine nucleoside phosphorylase deficiency.

Urinary orotidine and orotic acid have been determined in a patient with purine nucleoside phosphorylase (PNP) deficiency under various dietary therapeutic conditions. For this purpose a new procedure for the analysis of both compounds has been developed, consisting of prefractionation with Dowex 1X8, followed by two HPLC steps on a micro Bondapak NH2 and a micro Bondapak C18 column. With this method normal as well as slightly elevated excretions of orotic acid have been found in our patient. No evidence was obtained for inhibition of OPRT by purine (deoxy)nucleosides as a cause of pyrimidine starvation. A significant increase of urinary orotidine was found after loading with allopurinol. For comparison excretory values in a patient with ornithine transcarbamylase deficiency and also in a patient with orotic aciduria type I are shown. The possible cause of the slight increase in urinary orotic acid in our patient has been discussed.