Coupling of albumin flux to volume flow in skin and muscles of anesthetized rats.
Bovine serum albumin (BSA) labeled with 131I or 125I was injected intravenously in pentobarbital sodium-anesthetized rats, and tracer clearances into leg skin and muscles were measured over 30, 60, and 120 min. BSA labeled with the alternate tracer was used as vascular volume reference. Two minutes before injection of the tracer, a ligature was tied around one femoral vein to occlude outflow partially and raise capillary pressure in that leg. The unoccluded leg served as control. Skin and muscles of the occluded leg had variably and substantially higher water contents (delta W) than paired control tissues and slightly but consistently increased albumin clearances (CA). The delta CA/delta W, equivalent to the albumin concentration of capillary filtrate relative to plasma determined by linear regression, were as follows: leg skin 0.004 (95% confidence limits -0.001 to +0.009), muscle biceps femoris 0.005 (0.001-0.010), muscle gastrocnemius 0.011 (0.004-0.019), muscle tibialis anterior 0.016 (0.012-0.021). All these values are significantly less than 0.10, which corresponds to a reflection coefficient for serum albumin (sigma A) of 0.90. Convective coupling of albumin flux to volume flux in skin and muscles of intact, anesthetized rats is low, with sigma AS in the range 0.98 to greater than 0.99.
Department of Human Physiology, School of Medicine, University of California, Davis 95616.
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Renkin
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Gustafson-Sgro
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Sibley
D000818:Animals; D002196:Capillaries / Q000502:physiology; D005268:Femoral Vein / Q000502:physiology; D007457:Iodine Radioisotopes; D008297:Male; D009132:Muscles / Q000098:blood supply*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012039:Regional Blood Flow; D012710:Serum Albumin, Bovine / Q000493:pharmacokinetics*; D012867:Skin / Q000098:blood supply*
D007457:Iodine Radioisotopes; D012710:Serum Albumin, Bovine