transjunctional

Transjunctional is an adjective describing something that occurs across, or is situated at, a junction between two cells or tissues. In biology, the most common reference is to gap junctions, specialized intercellular channels that connect the cytoplasm of adjacent cells and permit direct chemical and electrical communication.

In electrophysiology, transjunctional voltage (V_j) is the difference in electrical potential between two connected cells across a gap junction. When two cells are coupled by gap junction channels, charge movement through those channels can generate transjunctional currents (I_j). The magnitude and kinetics depend on the properties of the connexin-based channels and their gating, which can be voltage-dependent and modulated by intracellular factors such as Ca2+ concentration and pH, phosphorylation state.

Transjunctional transport refers to the movement of ions, second messengers, and small metabolites through gap junctions from one cell to the other. This exchange enables synchronization of activity in cardiac and smooth muscle tissue and coordinated cellular responses during development and wound healing.

Clinically, alterations in transjunctional coupling—such as reduced gap junctional conductance due to altered connexin expression, ischemia, or disease—can disrupt tissue function and contribute to arrhythmias or developmental disorders.

See also gap junction, connexin, electrical synapse, intercellular communication.