Enhanced Uptake of Ifosfamide into GH3 Prolactinomas with Hypercapnic Hyperoxic Gases Monitored In Vivo by 31P MRS

Previously, 31P magnetic resonance spectroscopy (MRS) has been used to detect ifosfamide (IF) in vivo and to show that breathing carbogen (5% CO2/95% O2) enhances the uptake and increases the efficacy of IF in rat GH3 prolactinomas [Rodrigues LM, Maxwell RJ, McSheehy PMJ, Pinkerton CR, Robinson SP, Stubbs M, and Griffiths JR (1997). In vivo detection of ifosfamide by 31P MRS in rat tumours; increased uptake and cytotoxicity induced by carbogen breathing in GH3 prolactinomas. Br J Cancer 75, 62-68]. We now show that other hypercapnic and/or hyperoxic (5% CO2 in air, 2.5% CO2 in O2) gas mixtures also increase the uptake of IF into tumors, measured by 31P MRS. All gases caused an increased uptake (Cmax) of IF compared to air breathing, with carbogen inducing the largest increase (85% (P