Synthesis of pyrimidine nucleotide precursors in human and rat small intestinal mucosa

Abstract

Methods of thin-layer chromatography have been devised to study the interconversions of the pyrimidine biosynthetic precursors aspartic acid, carbamoylaspartic acid, dihydroorotic acid, and orotic acid in preparations of rat and human small intestinal mucosa. Whole mucosal homogenates, intact whole mucosal cells, cell homogenates, and intact crypt cells obtained from the rat and human jejunal whole mucosal homogenates were utilized. Homogenate preparations were most active in utilizing aspartate and carbamoylaspartate, whereas intact cells best formed orotic acid. Material obtained from the mucosal crypt areas, where cellular division occursm generally gave higher specific conversion rates than corresponding whole mucosal preparations. Human jejunal whole mucosal homogenates gave similar conversions to those of rat jejuno-ileal preparations. The methods have been scaled down to permit analysis of pyrimidine precursor metabolism in amounts of tissue obtainable by peroral biopsy.