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Table 2 Transportation of plasma contents in the steady state

From: Regulation of blood vascular permeability in the skin

Routes Molecules
Paracellular pathway Water molecules <3 nm molecular radius (i.e., urea, amino acids, glucose, ions)
Transcellular pathway Aquaporin channels Water (up to 40% of total hydraulic pathway)
Fluid-phase Caveolae Albumin [27, 46] intact native, acetylated and oxidized LDL [88, 89] IgG [44] transferrin and iron [90]
Undetermined IgG (bound to FcRn in endosomes after fluid-phase endocytosis [40, 41, 43, 49])
Receptor-mediated Caveolae Albumin (via gp60 receptor) [50,51,52] insulin (via unknown receptor) [49]
Clathrin Insulin [91] transferrin and iron (via transferrin receptor [92, 93]) gonadotrophin (via gonadotropin receptor [94])
Undetermined carrier vesicle IgG (via FcRn or FcγR2b [45, 95, 96]) LDL (via LDL receptor [97]) insulin (via insulin receptor [98])
Transendothelial channels
Vesiculo-vacuolar organelles
Direct probing by non-endothelial cells over blood vessels IgE (via FcεRI by mast cells) [58]