Effects of Extracellular Uridine or Ribose or PALA on Intracellular PRPP Levels

Here's that article showing that exogenous ribose can increase PRPP levels under some circumstances:

http://www.ncbi.nlm.nih.gov/pubmed/2480849?dopt=Abstract

This article shows that 100 uM but not 10 uM extracellular uridine can increase PRPP levels. The article also shows that PALA [phosphonacetyl-L-aspartate, an inhibitor of the aspartate transcarbamylase activity of the trifunctional CAD (carbamoyl-phosphate synthetase/aspartate transcarbamylase/dihydroorotase) enzyme] does not increase PRPP levels. The article also shows that methotrexate increases PRPP levels:

http://www.ncbi.nlm.nih.gov/pubmed/2411399?dopt=Abstract

This article shows that methotrexate increases PRPP levels (in combination with 5-fluorouracil, apparently) and cites reference 29, showing that PALA can increase PRPP levels by "20 to 50%":

http://www.ncbi.nlm.nih.gov/pubmed/7459888?dopt=Abstract

This article shows that uridine diphosphoglucose, at low but not higher doses, in response to intraperitoneal administration, increases intracellular PRPP levels in the liver and also increases the PRPP synthetase activity in the liver:

http://www.ncbi.nlm.nih.gov/pubmed/2435292


This article shows that iv uridine diphosphoglucose decreases PRPP levels in the liver (and in tumor cells) at high but not inordinately high doses:

http://www.ncbi.nlm.nih.gov/pubmed/2481854