The effect of plasma proteins on the capillary permeability in the rete mirabile of the eel (Anguilla vulgaris L.).

Measurements of transcapillary exchange of high-molecular dextrans, K+ and THO in the rete mirabile of the eel (Anguilla vulgaris L.) have been made under steady-state conditions while varying the amounts of plasma proteins in the perfusates. When the perfusates contained 20% or less horse serum the permeabilities of D-75 000, K% and THO increased significantly. The effect on the K+ permeability was irreversible while that on D-75 000 and THO was not. The permeability was unaffected when the perfusate contained 30% serum or more. Adding 1.3 g/100 ml bovine albumin to the perfusate maintained the D-75 000 and THO permeabilities unchanged while that of K+ appeared to increase. At an albumin content of 0.33 g/100 ml the effect was similar to that produced by low serum perfusates. Our main conclusion is that lack of the albumin fraction of the plasma proteins reversibly increases the intercellular pore area and irreversibly changes the K+ permeability of the cell membrane.