Pressure-permeability relationships in basement membrane: effects of static and dynamic pressures.

The glomerular basement membrane (GBM) is an important component of the filtration barrier that is the glomerular capillary wall. Previously GBM permeability has been investigated only under static pressures and often within a supraphysiological range. We used Matrigel as a model of GBM and formed membranes at the base of a filtration chamber. We measured membrane permeability under static and dynamic pressures. Matrigel membranes were size and charge selective toward neutrally and negatively charged dextrans. Their permeability (as measured by hydraulic conductivity) was found to decrease from 1.61 ± 0.06 to 0.75 ± 0.07 × 10-6cm ⋅ s-1 ⋅ cmH2O-1as static pressure increased from 6 to 78 cmH2O, an effect attributed to membrane compression. In comparison to static pressure, sinusoidal pressure waves with a mean pressure of 50 cmH2O decreased membrane permeability, e.g., fluid flux was reduced by a maximum of 2% to a value of 5.47 ± 0.38 × 10-5 cm/s; albumin clearance was reduced by a maximum of 5.2% to a value of 9.63 ± 1.06 × 10-6ml ⋅ cm-2 ⋅ s-1. Such changes were affected by the frequency of pressure wave application and could be attributed to a switching on and off of the membrane compression effect.