title: Hydraulic permeability coefficient and sodium steady-state luminal concentration of the in vivo perfused rat distal colon.
abstract: The distal colon (rat) was perfused in vivo at low rates (1-2 ml/h). Dialyzed polyethyleneglycol 4,000 (PEG) was used to vary the luminal osmotic activity (pi eff). Perfusate sodium concentration of 3.7 mmol 1-1 +/- 0.9 (SD) resulted in an effluent Na+ of 3.3 mmol 1-1 +/- 1.4. Potassium concentrations of 15 or 25 mmol 1-1 remained unaltered. At this cationic steady-state, transmural net water flux (Jv) was linearly correlated (r = -0.96, n = 24) to the logarithm of pi eff. Jv was zero at 634 mosm 1-1. Lp (microliters h-1 cm-2 mosm-1 l) was 0.195 at pi eff 85 mosm 1-1 and 0.046 at 1,050 mosm 1-1. These data characterize the distal colon as an epithelium with high capacity for salt conservation.
mesh_terms: D000818:Animals; D003106:Colon / Q000378:metabolism*; D007408:Intestinal Absorption; D009994:Osmolar Concentration; D010539:Permeability; D011092:Polyethylene Glycols / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water; D011092:Polyethylene Glycols; D012964:Sodium