Effect of supplemental dietary glutamine on methotrexate concentrations in tumors.

This study evaluated the effects of supplemental dietary glutamine (GLN) on methotrexate sodium concentrations in tumors and serum of sarcoma-bearing rats following the initiation of methotrexate. After randomization to a GLN diet (+GLN) or GLN-free diet (-GLN), tumor-bearing rats received 20 mg/kg of methotrexate sodium by intraperitoneal injection. The provision of supplemental GLN in the diet increased methotrexate concentrations in tumor tissues at 24 and 48 hours (38.0 +/- 0.20 nmol/g for the +GLN group vs 28.8 +/- 0.10 nmol/g for the -GLN group and 35.6 +/- 0.18 nmol/g for the +GLN group vs 32.5 +/- 0.16 nmol/g for the -GLN group, respectively). Arterial methotrexate levels were elevated only at 48 hours (0.147 +/- 0.007 microns/L for the +GLN group vs 0.120 +/- 0.006 microns/L for the -GLN group). Tumor morphometrics were not different between the groups but significantly greater tumor volume loss was seen even at 24 hours (-2.41 +/- 1.3 cm3 for the +GLN group vs -0.016 +/- 0.9 cm3 for the -GLN group). Tumor glutaminase activity was suppressed in both groups at 48 hours, but more so in the +GLN group (0.94 +/- 0.13 mumol/g per hour for the +GLN group vs 1.47 +/- 0.22 mumol/g per hour for the -GLN group). This study suggests that GLN may have therapeutic as well as nutritional benefit in oncology patients.