Table 1.

Mechanisms of stimulation of colonic water and electrolyte movements and motility by BAs. Adapted with permission from reference 5.

Mechanism	Mediators/Co-factors	Effects
Stimulation of intracellular mediators [6-11]	↑cAMP, epidermal growth factor receptor, and mediators including exchange protein directly activated by cAMP and Ca ++ ions	CFTR - induced chloride secretion
↑ intestinal permeability [12-15]	detergent or structure-activity properties of the BAs, TGR5 activation, ↓occludins	↑ secretion, ↑ motility, ↓ transepithelial barrier
Aquaporin channels [16,17]	↑ aquaporin channels 3 and 8 in rats	↑ water secretion
Enteroendocrine mechanisms [18-21]	↑ serotonin	↑ fluid and mucus secretion; activation of enteric neurons to ↑ colonic motility
Neurocrine mediation [21-25]	Activate basal TGR5 and submucosal cholinergic neurons; TGR5 activation of cholinergic and nitrergic myenteric neurons	↑ colonic motility, transit and secretion
Decreased sodium and water absorption [26]	↓ sodium potassium ATPase β1 unit in colon and α1 unit in proximal colon	↓ sodium and water reabsorption
↑ Myoelectrical activity [27-29]	Mechanism(s) unclear	↑ motility index
↑ HAPC [23]	↑ frequency of colonic propagating pressure wave sequences; mechanism(s) unclear	↑ colonic mass movements

ATP, adenosine triphosphatase; cAMP, cyclic adenosine monophosphate; CFTR, cystic fibrosis transmembrane conductance regulator