Diurnal changes in serum unconjugated bile acids in normal man.

Abstract

SUMMARY Unconjugated bile acids were measured using gas chromatography-mass spectrometry in the serum of two subjects throughout a 24 hour period and in two other subjects over a six hour period after breakfast. Unconjugated bile acids were found in all samples of serum and included cholic, chenodeoxycholic, deoxycholic, 3f3,7a-dihydroxy-5,/-cholanic (isochenodeoxycholic), ursodeoxycholic, 3/3,7,B3dihydroxy-5,/3cholanic (iso-ursodeoxycholic), 3,& hydroxy-5-cholenoic, and lithocholic acids. The maximum concentration of each bile acid generally occurred between breakfast and dinner and total unconjugated bile acid concentrations attained levels of between 2-3 ,umol/l. Concentrations increased after breakfast and were often as high as 30-40% of the conjugated bile acid glycocholate, but returned to fasting levels in the absence of lunch. The intestinal absorption of unconjugated bile acids is therefore of greater quantitative importance than was previously thought.

Extrahepatic deposition and cytotoxicity of lithocholic acid: Studies in two hamster models of hepatic failure and in cultured human fibroblasts

“…27, No. 2,1998 sham-operated animals, respectively, 99% and 76% of the radioactivity was in the form of unconjugated LCA. In the sham-operated group, around 9% and 10% of the radioactivity was associated with the respective glycine and taurine conjugates.…”

“…Their concentration in the systemic circulation is unique to each bile acid and can increase from two-to threefold postprandially from a fasting level of about 1 to 3 µmol/L. [1][2] Serum bile acids are mainly present in the amidated form; however, in normal man, the level of unconjugated bile acids exhibits a diurnal variation, attaining a rapid peak concentration of around 30% of the total serum bile acids after breakfast. 2 In cholestatic hepatobiliary disorders, bile acids accumulate in the systemic circulation, resulting in a 20-to 100-fold increase in their concentration.…”

“…[1][2] Serum bile acids are mainly present in the amidated form; however, in normal man, the level of unconjugated bile acids exhibits a diurnal variation, attaining a rapid peak concentration of around 30% of the total serum bile acids after breakfast. 2 In cholestatic hepatobiliary disorders, bile acids accumulate in the systemic circulation, resulting in a 20-to 100-fold increase in their concentration. 3 Under these conditions, serum levels of unconjugated bile acids, in particular that of chenodeoxycholic acid (CDCA), can increase dramatically if portal cirrhosis is present.…”

Biphasic regulation by bile acids of dermal fibroblast proliferation through regulation of cAMP production and COX-2 expression level

“…In the present study, the respective EC 50 for UDCA and CDCA was similar at both 2 and 20 h, at ϳ20 M, whereas that for DCA was just ϳ5 M. These EC 50 concentrations are clearly attainable in the systemic circulation during cholestasis, and possibly, even postprandially (2,29,44), and further underline the relevance of this bile acid effect. Even after 20 h of exposure, CA was without effect on stimulated cAMP formation, which is consistent with our previous reports (8,9), suggesting that the potency of the bile acid to inhibit stimulated cAMP formation varied with its hydroxylation state.…”

“…In the serum, bile acids are mainly in the amidated form. The level of unconjugated bile acids exhibits a diurnal variation, attaining a maximum concentration of 30 -40% of the total serum bile acids after breakfast (44). In several pathological conditions, tissues outside of the enterohepatic circulation can come in contact with high concentrations of both unconjugated and conjugated bile acids.…”