Influence of saline infusion on blood-tissue albumin transport.
Anesthetized rats were infused with lactated Ringer solution (LR) at constant rate for 30 or 60 min; delivered volume loads ranged from 0.03 to 0.08 ml/g body wt. Controls were given only a sustaining infusion of saline at 0.002 ml.g-1.h-1. Only 7-14% of the LR remained in the plasma at the end of the infusion; 76-88% entered the interstitial compartment, and 7-17% was excreted. The amount of plasma protein lost from the circulation with the extravasated fluid was studied simultaneously by two methods: 1) material balance in the whole animal and 2) changes in 131I-labeled albumin uptake (VA) and water content (VW) in individual tissues. The extravasation of 0.03-0.06 ml fluid/g body wt (75-160% initial plasma volume) did not significantly increase plasma protein extravasation in the whole rat. Nearly all of the sampled tissues of LR-infused rats had higher VW than controls. Tissue VA tended to increase with VW, but the regression slopes (delta VA/delta VW), a measure of the tracer albumin concentration of capillary filtrate relative to plasma, were low; skin, 0.006; paw, 0.018; skeletal muscles, 0.007; heart, 0.057; jejunum, 0.095; ileum, 0.045; cecum, 0.026; and colon, 0.027. These ratios are consistent with the very small loss of total plasma protein observed and attest to high solvent-drag reflection coefficients (sigma approximately equal to 1 - delta VA/delta VW): greater than 0.98 in capillaries of skeletal muscles, skin, and paw and 0.91-0.97 in heart and intestine.
Department of Human Physiology, School of Medicine, University of California, Davis 95616.
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Renkin
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Rew
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Wong
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O'Loughlin
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Sibley
D000818:Animals; D001794:Blood Pressure; D002196:Capillaries / Q000502:physiology; D007262:Infusions, Intravenous; D007552:Isotonic Solutions; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D000077325:Ringer's Lactate; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D012965:Sodium Chloride / Q000008:administration & dosage / Q000494:pharmacology*; D014018:Tissue Distribution
D007552:Isotonic Solutions; D000077325:Ringer's Lactate; D012710:Serum Albumin, Bovine; D012965:Sodium Chloride