The effect of tonicity and hypertonic solutions on microvascular permeability.
BACKGROUND
The effect of hypertonic saline (HS) on microvascular permeability is unclear. We hypothesized that varying degrees of tonicity and HS solutions alter microvascular fluid flux across the endothelium.


METHODS
Hydraulic permeability (L(p)) is a measure of water flow across the endothelial barrier. L(p) was measured in cannulated rat mesenteric venules using the modified Landis micro-occlusion technique. The effect of tonicity was tested by measuring L(p) after successive perfusions with Ringers' solutions of varying sodium chloride (NaCl) concentrations (85, 135, 185, and 235 mM) (n = 6). Additional venules were perfused with control Ringers' ([NaCl] = 135 mM) and measures of L(p) were obtained after subsequent perfusions with 7% NaCl followed by 7% NaCl with 6% dextran (n = 6).


RESULTS
Tonicity had a significant dose-dependent effect on L(p) (P < 0.0001). Perfusion with 7% NaCl significantly increased L(p) (P < 0.0001). The addition of 6% dextran to 7% NaCl significantly decreased L(p) compared with perfusion with 7% NaCl alone (P = 0.002).


CONCLUSIONS
We conclude that (1) tonicity influences microvascular permeability, (2) HS increases microvascular permeability, and (3) the addition of dextran to HS greatly attenuates this response. These findings suggest an important role for tonicity and a possible deleterious effect of HS in modulating microvascular permeability as well as the benefit of dextran with HS for maintaining intravascular volume.
Victorino
Gregory P
GP
Department of Surgery, University of California, San Francisco--East Bay, Alameda County Medical Center, Oakland, California 94602, USA. gvictorino@acmedctr.org
Newton
Christopher R
CR
Curran
Brian
B
D000818:Animals; D002199:Capillary Permeability / Q000187:drug effects*; D003911:Dextrans / Q000008:administration & dosage; D005260:Female; D009994:Osmolar Concentration; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D012965:Sodium Chloride / Q000008:administration & dosage; D013997:Time Factors
D003911:Dextrans; D012462:Saline Solution, Hypertonic; D012965:Sodium Chloride