How dehydration affects the thermoregulatory and osmoregulatory abilities of the golden spiny mouse Acomys russatus

The impact of increasing salinity in drinking water on resting metabolic rates (RMR) and non-shivering thermogenesis (NST) was studied in golden spiny mice Acomys russatus. Mice were acclimated to an ambient temperature of 27 °C under a photoperiod regime of 12L: 12D for three weeks. Salinity was increased gradually from 1 to 7% NaC1. Mice were kept for 14 days at each concentration. At the end of each acclimation to a given NaCl concentration, urine was collected and RMR and NST were determined. NST was measured as the maximal response of oxygen consumption (VO₂NA) and body temperature (T_bNA) to a noradrenaline (NA) injection. Results revealed that under 7% NaCl, urine volume decreased significantly while urine osmolarity increased significantly (p < 0.001 for both variables) compared to mice acclimated to 1% NaC1. Furthermore, body mass and RMR also decreased significantly (p < 0.05 for both variables) in 7% NaCl-acclimated mice compared to mice kept on 1% NaCl. However, NST capacity (the ratio of VO₂NA to RMR) significantly increased in such mice. The increased NST-capacity is due to the significant decrease of RMR values rather than a change in VO₂NA values. This is in agreement with results from other desert-adapted species, heat-acclimated and heat-adapted rats.