transepithelial chloride transport

Definition

Target type: biologicalprocess

The directed movement of chloride ions from one side of an epithelium to the other. [GOC:mah]

Transepithelial chloride transport is a fundamental process in many tissues, particularly in the gastrointestinal, respiratory, and renal systems. It involves the movement of chloride ions across epithelial cell layers, which are tightly connected by specialized junctions. This process is crucial for maintaining fluid balance, regulating electrolyte concentrations, and ensuring proper organ function. The movement of chloride ions occurs through a complex interplay of active and passive transport mechanisms.

The active transport of chloride ions is driven by the action of specific membrane proteins. The primary transporter responsible for chloride secretion is the cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel regulated by ATP binding and phosphorylation. CFTR is expressed in various epithelial tissues, including the airway, pancreas, and intestine. When activated, CFTR opens and allows chloride ions to flow out of the cell down their electrochemical gradient.

In addition to CFTR, other active transporters contribute to transepithelial chloride transport. These include the Na+/K+/2Cl- cotransporter (NKCC) and the K+/Cl- cotransporter (KCC). NKCC transports chloride ions into the cell along with sodium and potassium, while KCC facilitates the movement of chloride ions out of the cell.

The passive transport of chloride ions across epithelial cell layers is primarily mediated by chloride channels. These channels are present in both the apical and basolateral membranes of epithelial cells. The apical membrane, facing the lumen, often contains channels like CFTR, which are regulated by intracellular signaling pathways. The basolateral membrane, facing the interstitial fluid, typically expresses other types of chloride channels, including calcium-activated chloride channels (CaCC) and volume-regulated anion channels (VRAC).

Transepithelial chloride transport is tightly regulated by a variety of factors, including intracellular signaling pathways, hormonal cues, and environmental stimuli. For example, changes in intracellular calcium levels, cyclic AMP (cAMP) concentrations, and the activation of various kinases can modulate the activity of chloride channels and transporters. Hormones such as aldosterone and vasopressin can also influence transepithelial chloride transport by altering the expression and activity of specific transport proteins.

Dysregulation of transepithelial chloride transport can lead to various pathological conditions. For instance, mutations in the CFTR gene result in cystic fibrosis, a genetic disorder characterized by impaired chloride secretion in various tissues, leading to mucus buildup and organ dysfunction. Other disorders affecting transepithelial chloride transport include secretory diarrhea, dehydration, and electrolyte imbalances.

In summary, transepithelial chloride transport is a complex and tightly regulated process involving both active and passive mechanisms. This process is crucial for maintaining fluid balance, regulating electrolyte concentrations, and ensuring proper organ function. Dysregulation of this process can lead to various pathological conditions.'
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Proteins (3)

Compounds (22)