Inhibition of food deprivation induced hypovolemia by saline consumption in rats

Food deprivation hypovolemia has been observed in a variety of mesic and desert adapted rodents. Xeric adapted rodent species appear to lose intravascular volume in proportion with body weight loss during food restriction, while mesically adapted rodent species lose intravascular volume at a rate much in excess to body weight loss. The laboratory rat was chosen as a representative mesically adapted rodent species for the purpose of investigating this phenomenon. Acute isotonic saline stomach loads had no appreciable influence upon intravascular volume reparation induced by either 2 or 4 days of food deprivation. Free and forced choice saline solutions presented during starvation were noted to significantly inhibit hypovolemia, however, there was no evidence for reparation of carcass water losses. It is suggested that the availability of only water during fasting results in the premature termination of drinking due to cellular over-hydration. When water and a source of sodium are available the food deprived rat can more adequately maintain ad lib intravascular volume. There is presently no explanation for the absence of repaired carcass water.