PRESSURE-PERMEABILITY RELATIONSHIPS IN BASEMENT-MEMBRANE - EFFECTS OFSTATIC AND DYNAMIC PRESSURES

The glomerular basement membrane (GEM) is an important component of th e filtration barrier that is the glomerular capillary wall. Previously GEM permeability has been investigated only under static pressures an d often within a supraphysiological range. We used Matrigel as a model of GEM and formed membranes at the base of a filtration chamber. We m easured membrane permeability under static and dynamic pressures. Matr igel membranes were size and charge selective toward neutrally and neg atively charged dextrans. Their permeability (as measured by hydraulic conductivity) was found to decrease from 1.61 +/- 0.06 to 0.75 +/- 0. 07 x 10(-6) cm.s(-1).cmH(2)O(-1) as static pressure increased from 6 t o 78 cmH(2)O, an effect attributed to membrane compression. In compari son to static pressure, sinusoidal pressure waves with a mean pressure of 50 cmH(2)O decreased membrane permeability, e.g., fluid flux was r educed by a maximum of 2% to a value of 5.47 +/- 0.38 x 10(-5) cm/s; a lbumin clearance was reduced by a maximum of 5.2% to a value of 9.63 /- 1.06 x 10(-6) ml.cm(-2).s(-1). Such changes were affected by the fr equency of pressure wave application and could be attributed to a swit ching on and off of the membrane compression effect.