31P MRS of tumour metabolism in anaesthetized vs conscious mice

The injectable anaesthetics Hypnorm/Hypnovel, chloral hydrate and etomidate, were examined for their effects on C3H/He mouse core temperature and on the in vivo 31P MR spectra of KHT and SCCVII/Ha transplantable tumours, compared with conscious mice gently restrained in jigs. Hypnorm/Hypnovel at 0.1 mL/mouse i.p. reduced core temperature by 6 degrees C at 30 min after injection, returning to control levels by 100 min, but did not significantly alter the 31P MR spectra of either KHT or SCCVII/Ha tumours. Chloral hydrate at 300 mg/kg i.p. produced a 5 degrees C fall in mouse core temperature, at 25 min after injection, again returning to control levels by 100 min. This agent increased the Pi/total ratio to 155% of control at 15 min after injection in the KHT tumour, and to 170% of control at 45 min in SCCVII/Ha. Etomidate at 25 mg/kg i.p. reduced mouse core temperature by 7.5 degrees C by 20 min after injection, returning to only 84% of control by 100 min. This agent increased the Pi/total ratio by 260% in the KHT tumour 15 min after injection, without recovery to control values by 100 min. In SCCVII/Ha, a maximum increase in Pi/total of 360% was observed at 15 min after injection, with a return to control levels by 60 min. In addition, etomidate caused convulsions in the mice during the induction phase, and myoclonic jerking within 15 min of anaesthesia.