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Bile salts and calcium absorption.

ABSTRACT: 1. The study of the effect of bile salts on enhancing calcium absorption in the rachitic chick has been extended to bile salts not present in chick bile, e.g. glycine conjugates and bile alcohol sulphates. 2. Bile and bile salts cause an increase in calcium absorption from sparingly soluble calcium hydrogen phosphate when compared with a suspension of calcium hydrogen phosphate in saline. 3. If the bile ducts of normal rats are tied the absorption of calcium from calcium hydrogen phosphate decreases but can be restored by giving bile salts with the calcium salt. 4. Bile salts increase solubility in water of the sparingly soluble calcium salts, phytate and phosphate at pH values between 6 and 8. 5. Bile salts increase the solubility in lipid solvents of calcium in approximately the same proportion as they increase the absorption of calcium from the gut. 6. The physiological role of bile in calcium absorption and its mode of action are discussed.

SUBMITTER: Webling DD

PROVIDER: S-EPMC1265197 | biostudies-other | 1966 Sep

REPOSITORIES: biostudies-other

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Project description:Enterohemorrhagic Escherichia coli (EHEC), including serotype O157:H7, cause severe food-borne illness. On route to the human colon, they encounter and resist, numerous anti-microbial ingestion stresses. We hypothesize that these stresses cue EHEC to alter virulence properties. This study investigated the impact of bile salts on virulence properties and examined the genetic basis of the phenotypes. Established assays were used to examine adhesion to human epithelial cells, motility, verotoxin (VT) production and antimicrobial resistance with/without bile salt stress. Bacteria treated for 90 minute in DMEM plus 0.15% (w/v) bile salt mix demonstrated significantly enhanced adhesion to epithelial cells and resistance to several antibiotics but did not increase motility or VT production. To determine the genetic basis of these phenotypes a microarray experiment was conducted. EHEC strain 86-24, in mid-log phase of growth, were grown in DMEM pH 7.4 (control), or DMEM plus bile salt mix (0.15% w/v), for 90 minutes, statically at 37˚C, 5% CO2 prior to harvesting RNA for the microarray study. Four biological replicates were produced for each treatment. Microarray and gene expression analysis (semi-quantitative RT-PCR and beta-galactosidase reporter assays) of bile salt-treated EHEC revealed significant up-regulation of genes for lipid A modification, fimbriae, an efflux pump, and a two-component regulatory system relative to the bacteria grown in DMEM alone. This work points to several mechanisms that EHEC employs to resist the stresses of the human small intestine, notably efflux, antimicrobial resistance, and outer membrane alterations. Bile salts enhanced the virulence-related properties of increased adhesion and resistance to antimicrobials but not VT production or motility. This research contributes to our understanding of how EHEC senses and responds to host environmental signals and the mechanisms this pathogen uses to successfully colonize and infect the human host.

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Bile salts and calcium absorption.

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