Blood to tissue movement of albumin following plasmapheresis
We tested the hypothesis that reductions in the tissue uptake of albumin (125I-BSA) occur following plasmapheresis. Conscious, unrestrained Sprague-Dawley rats (240-320g), fitted with jugular catheters, and allowed a 72 h recovery, were plasmapheresed, resulting in a 25% plasma protein reduction. Control rats' catheters were manipulated but no blood was drawn. Sham rats were subjected to a cardiovascular perturbation similar to plasmapheresed animals, but without a plasma protein depletion. 125I-BSA was injected 1 h following plasmapheresis, and tissue uptake was determined over 70 min. Interstitial fluid was collected post-mortem. Plasmapheresis, but not sham, decreased 1 h total protein (5.4 0.2 to 4.7 0.2 g/dl, P 0.05), and albumin (3.3 0.1 to 2.9 0.1 g/dl P 0.05) concentrations and colloid osmotic pressure (20.2 1.0 to 16.5 1.2 mm Hg, P 0.05) below baseline. Plasmapheresis induced a decrease in the transcapillary colloid osmotic pressure gradient and a reduction in 125I-BSA tissue uptake in skeletal muscle (-56%), heart tissue (-39%), and skin (-36%) (P 0.05). We conclude that the reduced albumin transcapillary escape contributes to the rapid recovery of intravascular albumin stores following an acute protein depletion.