Sieving of electrolytes at capillary wall of cat skeletal muscle by osmotic water flow
Watson, P.D.
American Journal of Physiology 265(6 Pt 2): H1869-H1874
1993
ISSN/ISBN: 0002-9513 PMID: 8285225 Document Number: 415514
To test the hypothesis that a significant proportion of transcapillary water flow occurs through solute-restricting channels, we investigated the effects of transcapillary water movement on plasma electrolytes in isolated perfused cat skeletal muscle. The lower hindlimbs of anesthetized cats were perfused with a plasma-albumin solution and were weighed to determine transcapillary water movement. Osmolality was increased 60-70 mosmol/kgH-2O with sucrose, creating water fluxes of 8-10 ml cntdot min-1 cntdot 100 g-1, and the changes in the venous concentrations of sodium, potassium, and chloride were determined. The ion concentrations were all reduced by 6-7% with no significant difference between them. The amount of reduction was quantitatively explained by the flow of ion-free water from the interstitial space into plasma and the diffusion of electrolyte in the same direction. These findings support the hypothesis that important water-only transcapillary channels exist in mammalian skeletal muscle. The observations may also explain some of the electrolyte changes seen in intense exercise.