Pinocytic vesicle

The structure of the blood capillary wall is complex and varies in different organs and tissues. It consists of a single layer of endothelial cells joined together by intercellular junctions. Each endothelial cell, on an average, is 20-40 pm long, 10-15 pm wide, and 0.1-0.5 pm thick, and contains 10,000-15,000 uniform, spherical vesicles called plasmalemmal vesicles. These vesicles range in size between 60 and 80 nm in diameter. About 70% of these vesicles open on the luminal side of the endothelial surface, and the remaining open within the cytoplasm. Plasmalemmal vesicles are believed to be involved in the pinocytic transport of substances across the endothelium. The transition time of pinocytic vesicles across the cell is... 

The invaginated membrane then pinches off to form detached vesicles. The pinocytic vesicles (endosomes) migrate inwardly and fuse with lysosomes, which contain many lyosomal enzymes, to form secondary lyosomes. The ligand is degraded by the lysosomal enzymes, the degraded products are released and the membrane is recycled back to the plasma membrane. Alternatively, the secondary lysosomes can fuse with the cell membrane, leading to exocytosis of their contents, and the membranes are recycled back to the plasma membrane. 

Okada, C.Y. and Rechsteiner, M. (1982) Introduction of macromolecules into cultured mammalian cells by osmotic lysis of pinocytic vesicles. Cell 29, 33-41. 

Polymers (1a), (1b), (1d), (3a), (4a) and (5) were tested. Fi gure 3 shows the Endocytic Index (28) measured. The DIVEMA derivatives (1a), (3a) and (4a) Tfave no significant effect on the pinocytosis of 25j pyp (they do not influence the rate of formation of pinocytic vesicles). Polymer (1d) shows marked inhibition of pinocytosis at the highest dose.(This latter finding in vitro corresponds to in vivo results of Breslow et aTi (29)). They found that the removal of colloidal carbon from the blood of test animals is inhibited by high molecular weight DIVEMA). 

Pinocytic Vesicles Form from Coated Pits in the Plasma Membrane... 

Fig. 7. Transport pathways of a polymer in the liver 1 — diffusion through theintercellular junctions (molecular-size limited process) 2 — transcellular route of polymer transport into the bile including pinocytosis into hqtatocyte and exocytosis of the vesicles or residual bodies at the lateral side of the cell 3 — pinocytosis into the Kupffer cells occurs regularly, from either the central or the interstitial compartment. H.C. — hepatocyte E.C. — endothelial cell of capillary wall K.C. — Kupffer cell I.S. — interstitial space B.C. — bile canaliculi P — pinocytic vesicle L — lysosomes primary) S.L. — secondary lysosome R.B. — residual body N — nudeus...

Pinocytosis seems to be the main if not the only way in which a synthetic water-soluble polymer can enter an intact cell As almost all mammalian cells have developed a pinocytic function through which they can take many important metabolites they all can also capture synthetic polymers together with the surrounding fluid. The rate of polymer uptake by a particular cell is determined by the polymer concentration in the surounding medium and by the size and the rate of formation of pinocytic vesicles by the cell... 

Fig. 10. Accumulation of the polym in the cdls of the kidney tubular epBhelium of the mouse. The cross section through the omerulus (G) and projdmal tubules (T) in the fluorescence mode, 24 hours after intrav ous administration of polymm- III (see Fig. 11) at a rate of 0.1 g/kg. Fluorescence of granular depodtes is seen fuedominantly in the apical part of epithelM cdls (i.e., the part facing the tubular lumen) corresponding to the polymer accumulated in pinocytic vesicles and secondary lyso somes of these c s (arrows) (photo F.R.)...

Pinocytosis is a non-specific process in which minute droplets of extracellular fluid are engulfed by the plasma membrane. On detachment from the plasma membrane, pinocytic vesicles of less than 1 nm in diameter containing ions and small molecules migrate inward and may fragment into... 

Dunn, W.A. Hubbard, A.L. Aronson, N.N., Jr. Low Temperature Selectively Inhibits Fusion Between Pinocytic Vesicles and Lysosomes During Heterophagy of 1-Asialofetuin by the Perfused Rat Liver. J. Biol Chem. 1980, 255. 5971-5978. 

Bode, F., Baumann, K., and Kinne, R., 1976, Analysis of the pinocytic process in rat kidney. II. Biochemical composition of pinocytic vesicles compared to brush border microvilli, lysosomes and basolateral plasma membranes, Biochim. Biophys. Acta 433 294. 

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