IN-VIVO F-19 NMR-STUDIES OF HYPERTHERMIA - HYDROPHOBIC ENVIRONMENTS PROBED BY HALOTHANE

The steady-state distribution of the general anesthetic halothane in d ifferent rat tissues, including a renal adenocarcinoma with and withou t hyperthermia treatment, has been evaluated by in vivo F-19 NMR spect roscopy. The F-19 spectra of halothane (which is a hydrophobic probe) from within tissue show differences in the partitioning between normal rat tissues and adenocarcinoma. Muscle, as a control tissue, exhibits a single large resonance around 0 ppm. However, the adenocarcinoma ex hibits two slow-exchanging resonances separated by 0.3 ppm with the on e at the more hydrophobic chemical shift being more sensitive to hyper thermia treatment. The results from this tumor model suggest that F-19 NMR spectroscopy may be useful first in detecting a change in hydroph obic environments using a lipophilic probe such as halothane, and seco ndly in monitoring the effects of hyperthermia, a treatment whose effe ctiveness may involve changes at the level of the plasma membrane. Und er conditions of continuous delivery, a resonance which is not detecte d in the spectra of halothane in excised tissue appears 5 ppm downfiel d from the resonance for halothane localized in tissues. A rotating fr ame experiment is used to show that this resonance is derived from ane sthetic absorbed on the tissue surface.