title: Extracellular fluid and plasma volumes during water immersion in nephrectomized dogs.
abstract: Extracellular fluid volume (ECF, [125I]iothalamate space), blood volume (BV, 51Cr-labeled erythrocyte space), and hematocrit were measured continuously to study the kinetics of fluid movements between intracellular, interstitial, and plasma compartments during water immersion (WI) at 38 degrees C in seven splenectomized and acutely nephrectomized dogs. ECF and plasma volume (PV) increased linearly during WI by 10 +/- 2 ml/kg (4% of initial ECF volume, P less than 0.05) and 12 +/- 2 ml/kg (33% of initial PV, P less than 0.05), respectively, above the control level by 120 min of WI. We estimate that 83% of the fluid entering the intravascular compartment is derived from the intracellular space at 120 min of WI. The results of this study indicate that WI leads to a sustained fluid movement of intracellular fluid toward the intravascular compartment. The increase in interstitial hydrostatic pressure (wick method) by 28.5 mmHg from the control level at 5 min of WI in response to the external water pressure exceeds the increase in mean capillary pressure by 10-11 mmHg relative to the control level. We postulate that this negative hydrostatic pressure gradient across the capillary wall leads to an increase in PV during WI.
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000378:metabolism; D001810:Blood Volume; D004285:Dogs; D004911:Erythrocyte Volume; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D006400:Hematocrit; D006874:Hydrostatic Pressure; D007101:Immersion; D009392:Nephrectomy
chemical_list: D001798:Blood Proteins