The Micellar Sink

Abstract

Although the importance of mixed micelles in the solubilization and biliary excretion of lipids is established, little is known about a possible role of mixed micelles in the excretion of other biliary solutes. Ultrafiltration and ultracentrifugation techniques were used to investigate the interaction between substances that are excreted in bile and biliary mixed micelles. Substances (urea, erythritol, sucrose) excreted in bile at concentrations equal to, or less than, that in plasma did not show an association with mixed micelles, whereas substances (indocyanine green, iopanoic acid, rose bengal, unconjugated and conjugated sulfobromophthalein, and conjugated bilirubin) excreted in bile at high concentration relative to plasma did. The percentage of these latter substances in bile associated with micelles varied from 26 to 93% and was relatively independent of concentration. In addition to their association with mixed micelles, these test solutes formed self-aggregates that were stabilized primarily by ionic bonds, and only a small percentage (range = 0-5%) of these solutes were present in bile in the form of monomer or complexes small enough to pass a 5,000-mol wt membrane.These findings offer a possible explanation for the increase in sulfobromophthalein, bilirubin, and indocyanine green maximal biliary excretory rate produced by bile salt infusion, and suggest that the concentrative transport into bile of endogenous compounds and xenobiotics may result from their incorporation into mixed micelles and other macromolecular complexes.

The skin microbiome of caspase‐14‐deficient mice shows mild dysbiosis

“…They reported that Proteobacteria formed the most abundant phylum with a predominance of the Pseudomonas and Janthinobacterium genera. A similar C57BL/6 skin microbiome was described by Scharschmidt et al (22). Tavakkol et al (23) analysed the dorsal trunk skin of C57BL/6 mice and reported that this part of the skin, unlike the above-mentioned ear skin, was mainly inhabited by staphylococci, which are part of the phylum Firmicutes.…”

Effects of Submicellar Bile Salt Concentrations on Biological Membrane Permeability to Low Molecular Weight Non-Ionic Solutes

“…Therefore, at higher bile salt concentrations that induce CF leakage from large unilamellar vesicles, we limit our conclusions to the observation that vesicles that still contain CF do not display any change in water permeability. Indeed, it is likely that alterations in membrane structure at concentrations near membrane solubilization are responsible for the transient increases in permeability to larger molecules observed by some groups (Scharschmidt & Schmid, 1978; and TUDC (open bars) on P f of rat liver microsomal membranes at 37°C. Neither bile salt significantly alters P f of rat liver microsomal membranes.…”

Transport of conjugated bilirubin and other organic anions in bile: relation to biliary lipid structures.

“…Physiological studies of bilirubin and other organic anion secretory rates in bile showed a strong correlation with bile acid secretory rates under stimulated conditions but not during fasting (3)(4)(5)(6)(7)(8). This observation led to studies that have concluded that a strong relationship exists between biliary mixed-lipid micelles and bilirubin in addition to a variety of other organic anions, although the precise nature of the putative micellar-organic anion interaction has remained unclear (9)(10)(11)(12)(13)(14)(15). Thus, a more recent study examining this relationship failed to support the concept of a physicochemical association between biliary lipids and conjugated bilirubin (15).…”