Albumin reduces basement membrane hydraulic conductance in part due
to arginyl sidegroups.
Katz, Murray A., and Margaret L. Lamarche.
Benjamin W. Zweifach Microcirculation Laboratories, Tucson Veterans
Affairs Medical Center, 2Departments of Medicine and Physiology,
University of Arizona College of Medicine, Tucson, AZ 85723
APStracts 2:0231H, 1995.
Albumin reduces capillary hydraulic conductance (Lp) even at low
concentrations. To determine if part of this barrier protective
effect might be extracellular, we studied bovine serum albumin (BSA)
on Lp of self assembled basement membrane (Matrigel_). Lp with Tris
buffer superfusate was stable at (1.77 +/- .22 SEM) x 10-5 cm x sec-1
x cm H2O-1 over several hours. At 0.1 g/dl BSA experimental/control
(Tris) Lp fell to 83.1 +/- 6.0% (2P<.025), with decreases to
72.4 +/- 3.7% at 1 g/dl (2P<.005), 45.3 +/- 5.1% at 2.5 g/dl
(2P<.001), and 45.0 +/- 4.8% at 4.0 g/dl (2P<.001). In
separate experiments BSA arginine groups were neutralized by 1,2
-cyclohexanedione (CHD-BSA), and experimental/control Lp were
measured. At 2.5 g/dl, CHD-BSA depressed Lp to 54.4 +/- 4.8% while
unmodified BSA reduced Lp to 40.8 +/- 3.5% of Tris control (2P nearly
equal to .05). Finally, soluble arginine at 3X and 6X the arginine in
BSA was added to BSA superfusate. For 3X Lp rose to 120 +/- 8% of BSA
level and for 6X to 129 +/- 9% (2P<.05). We conclude that some
part of the albumin protective effect is very likely due to
consequences on extracellular matrix, that at least 18 to 22% of this
effect is related to arginine groups on albumin when computed from
Lp, and up to 34% when viscosity is taken into account. Membrane
saturable arginine-binding sites can be unbound with arginine thus
nullifying part of the barrier protective effect of BSA.
Received 14 April 1995; accepted in final form 25 May 1995.
APS Manuscript Number H362-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 June 1995.