Time‐dependent effects of anesthetic agents on 31P NMR high‐energy phosphates in KHT and RIF‐1 fibrosarcomas

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Abstract
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 °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) + β‐nucleoside triphosphate (β‐NTP)/inorganic phosphate (Pi) ratios; and (iii) effect on temporal variability of PCr+β‐NTP/Pi ratios. In terms of overall duration, AZ was the clear preference. Although the maintenance of 37 °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 + β‐NTP/Pi ratios were constant over the entire 80 min period for both lines. With PB, PCr + β‐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.