Water flux through porcine aortic tissue due to a hydrostatic pressure gradient

The water flux through preparations of porcine aorta has been investigated. After an initial unsteady period a stable flux of approximately 2 mul/cm2-h was reached and this flux rate remained constant for several hours. Under the experimental conditions which were maintained (110 mm Hg pressure drop across a 2 mm thick section of tissue) this total flux corresponds to a hydraulic conductivity of less than or equal to 7.0 X 10(-13) cm4/dyne-sec. Since these data were obtained in tissue samples where the endothelial layer was not intact, they represent values which are in fact larger than the actual in vivo condition where the endothelial barrier would serve as an additional resistance. Thus, they demonstrate that the transmural flux of water across the aorta wall in vitro due to a pressure gradient is extremely small and, therefore, that other mass transfer mechanisms may be significant.