TIME-DEPENDENT EFFECTS OF ANESTHETIC AGENTS ON 31P 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 P-31 NMR phosphocreatine (PCr) + beta-nucleoside triphosphate (beta-NTP)/inorganic phosphate (P(i)) ratios; and (iii) effect on temporal variability of PCr + beta-NTP/P(i) 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/P(i) ratios were constant over the entire 80 min period for both lines. With PB, PCr + beta-NTP/P(i) 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.