FACTORS AFFECTING ENDOGENOUS OXALATE SYNTHESIS AND ITS EXCRETION IN FECES AND URINE IN RATS

Abstract

The feces as well as urine of rats fed diets supplemented with 3% glycine and 5.2% hydroxyproline contain unexpectedly high amounts of endogenously formed oxalate. That intestinal microorganisms do not synthesize significant amounts of oxalate was indicated by the findings that oral tetracycline had no effect on oxalate excretion and that germ-free rats excreted more oxalate than conventional rats. Since little i.p. injected [14C]oxalate appeared in the feces, and rat intestinal mucosa homogenates were found to produce oxalate from a variety of precursors of which glyoxylic acid was by far the most important, it is probable that the intestinal mucosa may be an important source of fecal oxalate observed in these studies. Of weanling rats fed complete diets supplemented with glycine and hydroxyproline, 90% developed urinary stones in 38 days. Apparently, in the treatment of patients with histories of calcium oxalate urolithiasis, more concern should be directed towards the feeding of diets high in precursors of endogeneous oxalate synthesis.