Bile salts and ileal calcium transport in rats: a neglected factor in intestinal calcium absorption

Abstract

Ileum displays little active transcellular calcium (Ca2+) absorption but is credited with the bulk of Ca2+ absorbed in vivo. We examined the effect of taurodeoxycholic acid (TDC, 2 mM), a bile salt, on mannitol (MN, a marker of intercellular solute traffic) and Ca2+ fluxes in rat ileum. In the absence of electrochemical gradients between the mucosal (M) and serosal (S) bathing media in an Ussing chamber, net flux (Jnet) was observed in the S-to-M direction for both MN and Ca2+, i.e., the unidirectional secretory S-to-M flux (Js-->m) exceeded the absorptive M-to-S flux (Jm-->s). Mucosal TDC caused simultaneous increase in transepithelial conductance and Js-->m for both MN and Ca2+. This was followed by even greater increases in MN and Ca2+ Jm-->s, so that ultimately Jm-->s equaled Js-->m in each case. In control tissue, Js-->m for Ca2+ appeared to permeate exclusively through the intercellular MN pathway while part of Jm-->s for Ca2+ appeared to traverse through a non-MN route. After the TDC-induced increase in intercellular solute permeability, both Ca2+ fluxes appeared to traverse through the aqueous MN conduit. During the postprandial state, the presence of bile salts and the relative abundance of Ca2+ in ileal lumen can cause bulk Ca2+ absorption through the intercellular pathway.

A Soluble Flavonoid-glycoside, αG-Rutin, Is Absorbed as Glycosides in the Isolated Gastric and Intestinal Mucosa

“…This procedure has been used for the transport of flavonoids in the gastrointestinal mucosa. 13) Hu et al 14) demonstrated that intestinal tissue was viable for 3 h with an Ussing chamber. We also measured TEER and confirmed the viability of the above.…”

Evidence for Involvement of 17β-Estradiol in Intestinal Calcium Absorption Independent of 1,25-Dihydroxyvitamin D3 Level in the Rat

“…Various factors, including general anesthesia, (58) intraluminal pH (59) and glucose, (60,61) and bile salt concentration (62) are known to affect intestinal calcium transport. Therefore, calcium influx may have been reduced, while calcium efflux remained unaffected, resulting in a negative calcium transport in the treated groups.…”

Milk Alkali Syndrome and the Dynamics of Calcium Homeostasis

“…However, calcium absorption may be as good or even better with meals (28,29). Such a result may have to do with the acidity of the meal and its carbohydrate content, protein breakdown, and the presence of bile salts (30,31).…”