The effects of isoflurane and halothane on blood flow and 31 P NMR spectra in murine RIF‐1 tumors

The principal aim of these studies was to evaluate the utility of isoflurane and halothane for NMR investigations of tumor physiology. In vivo 31 P and 2 H NMR were used to examine RIF‐1 tumors before, during, and (for 31 P) after anesthesia. In tumors, halothane decreases blood flow, [PCR]:[NTP], and pH indicated by the P 1 chemical shift (pH nmr ), while it increases [ P 1 :[NTP]; effects consistent with well‐established cardiovascular effects of halothane. Isoflurane does not affect tumor blood flow or [PCr]:[NTP], but increases tumor [ P 1 :[NTP] and decreases tumor pH nmr . In vivo 31 P NMR measurements of normal mouse liver (upper abdomen) indicate that isoflurane has a similar effect in the liver. Although the mechanism for these effects is unknown, observation of a split P 1 peak during isoflurane anesthesia suggests that a pool of P 1 in a lower pH environment may become evident under isoflurane anesthesia. Regardless of the cause for increased [ P 1 :[NTP] and decreased pH nmr the utility of isoflurane anesthesia for 31 P NMR studies of energy metabolism is limited.