Hydraulic and diffusional permeabilities of isolated outer
medullary descending vasa recta from the rat.
Turner, Malcolm R., and Thomas L. Pallone.
Division of Nephrology, M.S. Hershey Medical Center, Pennsylvania
State University, Hershey, PA 17033 and Division of Nephrology,
University of Maryland School of Medicine, Baltimore, MD 21201
-1595
APStracts 3:0279H, 1996.
Hydraulic and diffusional permeabilities of isolated outer medullary
descending vasa recta from the rat. Water permeates many microvessel
walls via a pathway shared with small hydrophilic solutes and also
via an exclusive water pathway. In outer medullary descending vasa
recta (OMDVR), the relationship between diffusional permeabilities to
water and sodium indicates the existence of an exclusive water
pathway and suggests that of a shared pathway. We investigated the
latter possibility by estimating hydraulic permeability (L p ) and
diffusional permeability to 3 H-raffinose (P raf ), in isolated
perfused OMDVR. The product of L p and osmotic reflexion coefficient
of albumin (L p s a) was 1.56+/-0.19 x 10 -6 cm s -1 mm Hg -1 (n=28),
calculated from transmural volume fluxes induced by perfusate-to-bath
differences in albumin oncotic pressure (DP a ). P raf in the same
vessels was 40.1+/-7.5 x 10 -5 cm s -1 , when DP a was zero. In
separate experiments, sa was at least 0.89+/-0.10 (n=17). L p s a
correlates with P raf , indicating that OMDVR contain a shared
pathway for convection driven by DP a and for diffusion of small
hydrophilic solutes.
Received 30 January 1996; accepted in final form 21 June 1996.
APS Manuscript Number H88-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 July 1996