Table 2 Transportation of plasma contents in the steady state
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 | 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] | ||