Pharmacokinetics and toxicology of therapeutic proteins: Advances and challenges

Table 2 Transport mechanisms for proteins from systemic circulation across capillary endothelia[22]

Type of capillary endothelium	Barrier/transport mechanism	Particle size subject to passage	Typical tissues
Continuous (non-fenestrated)	Basal lamina membrane supported by collagen	50-110 nm	Muscle, central nervous system, bone, skin, cardiac muscle
Fenestrated	Large pores, open fenestrae, intracellular junctions, basal lamina	50-800 nm	Renal glomeruli, intestinal villi, synovial tissue, endocrine glands, choroid plexus (brain)
Discontinuous (sinusoidal)	Large pores (fenestrae), pinocytotic vesicles	1000-10  000 nm	Liver, spleen, bone marrow, postcapillary venules of lymph nodes