In vivo hydraulic conductivity of muscle: Effects of hydrostatic pressure

E. L. Rasheid Zakaria, Joanne Lofthouse, Michael F. Flessner

Research output: Contribution to journalArticlepeer-review

55 Scopus citations


We and others have shown that the loss of fluid and macromolecules from the peritoneal cavity is directly dependent on intraperitoneal hydrostatic pressure (P(ip)). Measurements of the interstitial pressure gradient in the abdominal wall demonstrated minimal change when P(ip) was increased from 0 to 8 mmHg. Because flow through tissue is governed by both interstitial pressure gradient and hydraulic conductivity (K), we hypothesized that K of these tissues varies with P(ip). To test this hypothesis, we dialyzed rats with Krebs-Ringer solution at constant P(ip) of 0.7, 1.5, 2.2, 3, 4.4, 6, or 8 mmHg. Tracer amounts of 125I-labeled immunoglobulin G were added to the dialysis fluid as a marker of fluid movement into the abdominal wall. Tracer deposition was corrected for adsorption to the tissue surface and for local loss into lymphatics. The hydrostatic pressure gradient in the wall was measured using a micropipette and a servo-null system. The technique requires immobilization of the tissue by a porous Plexiglas plate, and therefore a portion of the tissue is supported. In agreement with previous results, fluid flux into the unrestrained abdominal wall was directly related to the overall hydrostatic pressure difference across the abdominal wall (P(ip) = 0), but the interstitial pressure gradient near the peritoneum increased only ~40% over the range of P(ip) = 1.5-8 mmHg (20-28 mmHg/cm). K of the abdominal wall varied from 0.90 ± 0.1 x 10-5 cm2 · min-1 · mmHg-1 at P(ip) 1.5 mmHg to 4.7 ± 0.43 x 10-5 cm2 · min-1 · mmHg-1 on elevation of P(ip) to 8 mmHg. In contrast, for the same change in P(ip), abdominal muscle supported on the skin side had a significantly lower range of fluid flux (0.89-1.7 x 10-4 vs. 1.9-10.1 x 10-4 ml · min-1 · cm-2 in unsupported tissue). The differences between supported and unsupported tissues are likely explained in part by a reduced pressure gradient across the supported tissue. In conclusion, the in vivo hydraulic conductivity of the unsupported abdominal wall muscle in anesthetized rats varies with the superimposed hydrostatic pressure within the peritoneal cavity.

Original languageEnglish (US)
Pages (from-to)H2774-H2782
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number6 42-6
StatePublished - 1997
Externally publishedYes


  • Convection
  • Interstitium
  • Peritoneal cavity
  • Solvent drag
  • Transport

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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