Conjugated bile salts

Effect of pH. The effect of pH on the deoxycholate series of bile salts in 0.15N NaCl at 20° and 36°C. is summarized in Figure 8. Solutions of free and glycine conjugated bile salts were studied between pH 9.2 and their precipitation pH (NaDC == 6.95, NaGDC = 4.9). Taurine conjugates were studied between pH 10 and 1.6. 

Conjugated bile salts are normally absorbed in the terminal ileum. Disease of the terminal ileum (eg, Crohn s disease) or surgical resection leads to malabsorption of bile salts, which may cause colonic secretory diarrhea. The bile salt binding resins cholestyramine or colestipol may decrease diarrhea caused by excess fecal bile acids (see Chapter 35 Agents Used in Hyperlipidemia). The usual dose is 4-5 g one to three times daily before meals. Side effects include bloating, flatulence, constipation, and fecal impaction. In patients with diminished circulating bile acid pools, further removal of bile acids may lead to an exacerbation of fat malabsorption. These agents bind a number... 

Mita S, Suzuki H, Akita H, et al. Vectorial transport of unconjugated and conjugated bile salts by monolayers of LLC-PK1 cells doubly transfected with human NTCP and BSEP or with rat Ntcp and Bsep. Am J Physiol Gastrointest Liver Physiol 2006 290 G550-G556. 

Cysteine Mercaptopyruvic acid Cysteamine, taurine3 Cysteamine is a component of Co A Taurine is a component of conjugated bile salts... 

Additional reactions of glycine include its ability to become conjugated with bile acids to form conjugated bile salts (see Chapter 19), formation of heme (Chapter 7), formation of purine nucleotides (Chapter 10), formation of creatine (see later), and the formation of hippuric acid from benzoic acid. In the last case, an amide linkage is formed between the carboxyl group of benzoic acid and the amino group of glycine. 

Figure 2. Model of a conjugated bile salt molecule (side view) which shows the spatial arrangement of the hydrophobic and hydrophilic face. "Reproduced with permission from Ref. 23. Copyright 1973, Plenum Press. "...

The bile salt-dependent pathway relies on conjugated bile salts being excreted from the hepatocytes into the hepatic canaliculi via the... 

Hjelm RP, Schteingart CD, Hofmann AF, and Thiyagartyan P. Structure of Conjugated Bile Salt-Fatty Acid-Monoglyceride Mixed Colloids Studies by Small-Angle Neutron Scattering./PAyi Chem B 2000 104 197-211. 

Kratohvil JP, Hsu WP, Jacobs MA, Aminabhavi TM, and Mukunoki Y. Concentration-Dependent Aggregation Patterns of Conjugated Bile-Salts in Aqueous Sodium-Chloride Solutions—a Comparison between Sodium Tau-rodeoxycholate and Sodium Taurocholate. Colloid Polymer Sci 1983 261 781-785. 

Deconjugation of bile acids may become excessive when bacterial overgrowth occurs in the small intestine. This condition is referred to as the stagnant loop or blind loop syndrome and is characterized by diarrhea, often accompanied by steatorrhea because of a decrease in the effective concentration of conjugated bile salts and a reduction in the fat-absorptive capacity of the small intestine. 

PIO. Playoust, M. R., and Isselbacher, K. J., Studies on tbe transport and metabolism of conjugated bile salts by intestinal mucosa. J. Clin. Invest. 43, 467-476 (1964). 

JG Spenney, BJ Johnson, BI Hirschowitz, AA Mihas, R Gibson. An 125I radioimmunoassay for primary conjugated bile salts. Gastroenterology 72 305, 1977. 

Fig. 10. Physical state and percent ionization of the common free, G-conjugated, and T-conjugated bile salts as functions of pH. (From ref. 6 with permission.)...

---