Time-dependent effects of anesthetic agents on31P NMR high-energy phosphates in KHT and RIF-1 fibrosarcomas

Previous studies have reported significant radiobiological and hemodynamic effects associated with sodium pentobarbital (PB) anesthetization. The present work contrasts the effects of PB with azaperone-ketamine (AZ) in RIF-1 and KHT tumors while animal body core temperature is maintained at 37 degrees C. The primary aims were to evaluate both agents in terms of: (i) duration of anesthetic; (ii) effect on absolute levels of 31P NMR phosphocreatine (PCr) + beta-nucleoside triphosphate (beta-NTP)/inorganic phosphate (Pi) ratios; and (iii) effect on temporal variability of PCr + beta-NTP/Pi ratios. In terms of overall duration, AZ was the clear preference. Although the maintenance of 37 degrees C core temperature significantly reduced overall durations for both anesthetics, AZ animals invariably remained immobile for a minimum of 80 min. For PB, durations were highly unpredictable. With AZ, mean PCr + beta-NTP/Pi ratios were constant over the entire 80 min period for both lines. With PB, PCr + beta-NTP/Pi ratios were lower in relation to AZ for KHT at select timepoints, but highly variable among RIF-1 tumours. Since ratios under PB varied substantially with time for RIF-1 lines, measurements taken with PB are clearly not representative of the control state. Furthermore, in light of the consistent and reproducible results obtained with AZ, this anesthetic is considered a marked improvement over PB for animal studies of this nature.