Glycerol-induced hyperhydration: its effects on fluid compartments in the rat

Glycerol solutions are a safe, effective means to achieve a long-term state of hyperhydration. The effects of glycerol-induced hyperhydration (GIH) on the total body water (TBW), extracellular fluid (ECF), plasma volume (PV), intracellular fluid (ICF), and interstitial fluid (ISF) were investigated in the rat. Ten rats were intragastrically administered either 20 ml/kg of water or 5% glycerol. The TBW, ECF, and PV were determined by 3H2O, 14C-inulin and dye dilution, respectively at 2 h postingestion. Urine volumes and fluid retention were measured throughout the experiment. Fluid retention was increased by 50% with the 5% glycerol solution when compared to water. When the fluid compartment data at 2 h are expressed in terms of percent of body weight, the TBW and ICF of the glycerol-treated rats exceeds that of the water-treated rats, and the values for the ECF, PV, and ISF were similar after the glycerol solution and water regimens. Glycerol solutions appear to have a greater effect in expanding TBW and ICF than equal volumes of water.