transcellular

Transcellular refers to processes that move substances across a cell, typically across an epithelial or endothelial barrier. It describes transport from one surface of the cell to the opposite side, through the cytoplasm, as opposed to paracellular transport, which moves between cells via intercellular junctions. Transcellular transport usually involves uptake at the apical membrane, intracellular trafficking through endosomes or the cytosol, and release at the basolateral membrane, or the reverse.

The mechanisms of transcellular transport include transporter proteins and channels that mediate uptake and efflux, as well as vesicular routes such as endocytosis, transcytosis, and exocytosis. This pathway may require energy for active transport and can involve complex routing through intracellular compartments before the substance exits on the opposite side. Transcellular movement often exhibits directional regulation, reflecting the physiological role of the tissue.

Biological contexts where transcellular transport is important include nutrient absorption in the intestinal epithelium and reabsorption in renal tubules, as well as movement across barriers such as the blood-brain barrier. It also underlies transcytosis of macromolecules in certain tissues and, in clinical and pharmacological contexts, influences drug absorption and delivery. Understanding the balance between transcellular and paracellular routes helps explain normal physiology and how barrier dysfunction can contribute to disease.

See also: paracellular transport, transcytosis, endocytosis, exocytosis.