Table 1.

Mechanisms of colonic water and electrolyte movement in bile acid malabsorption

Mechanism (ref. #)	Mediators/co-factors	Effects
Stimulation of intracellular mediators (32–34)	↑cAMP, epidermal growth factor receptor, and mediators including exchange protein directly activated by cAMP and calcium++ ions	CFTR - induce chloride secretion
↑ intestinal permeability (36–41)	detergent or structure activity properties of the bile acids, TGR5 activation, ↓occludins	↑ secretion, ↑ motility, ↓ transepithelial barrier
Aquaporin channels (42,44,45)	↑ aquaporin channels 3 and 8 in rats	↑ water secretion
Enteroendocrine mechanisms (46,47)	↑ serotonin	↑ fluid and mucus secretion
Neurocrine mediation (47–49)	activate basal TGR5 and submucosal cholinergic neurons	↑ colonic motility and secretion
Decreased sodium and water absorption (50)	↓ sodium potassium ATPase β1 unit in colon and α1 unit in proximal colon	↓ sodium and water reabsorption

cAMP=calcium and cyclic adenosine monophosphate; CFTR=cystic fibrosis transmembrane conductance regulator