Transcellularly

Transcellularly is an adverb used in physiology and related fields to describe the movement of a substance through a cell, crossing both the apical and basolateral membranes and passing through the cell interior. This route contrasts with paracellular transport, which occurs between cells through tight junctions. Transcellular transport can involve various cellular processes and is a key mechanism for absorption, secretion, and barrier function.

Transport across a cell typically involves membrane proteins and intracellular pathways. Substances may cross via carrier- or channel-mediated transport, vesicular trafficking, endocytosis, or exocytosis, and the process can be active or passive depending on the energy requirements and the specific solute. The transcellular route often requires coordination between apical and basolateral membranes, as well as cytosolic steps that move the solute from one side to the other.

In biological systems, transcellular transport is central to nutrient absorption and homeostasis. For example, in the intestinal epithelium, sugars and amino acids are commonly absorbed transcellularly through specific transporters, while water follows osmotically through channels or with solutes. In the kidney, many solutes are reabsorbed transcellularly along the tubules, contributing to urine concentration and electrolyte balance. The transcellular route also plays a role at biological barriers, such as the intestinal lining and the blood-brain barrier, where selective transport governs permeability.

Etymologically, transcellularly combines trans- (across) with cellular, and the form is used to describe transport pathways that traverse a cell, as opposed to movement between cells.