AJP - Gastrointestinal and Liver Physiology, Vol 238, Issue 1 10-G17, Copyright © 1980 by American Physiological Society
Bile acid structure and bile formation: a comparison of hydroxy and keto bile acids
R. B. Sewell, N. E. Hoffman, R. A. Smallwood and S. Cockbain
The effect of four bile acids, taurocholic (TC), taurochenodeoxycholic
(TCDC), tauro-3 alpha,7 alpha-dihydroxy-12-keto-5 beta-cholanoic (T12K),
and cholic (C), on bile lipid and water secretion was studied in the bile
fistula cat over a 20-fold range of bile acid secretion rates. The critical
micellar concentration (CMC) and lecithin-solubilizing capacity of TC,
TCDC, and T12K were measured in vitro. T12K and C produced a greater
choleresis than TC or TCDC; phospholipid secretion was strikingly reduced
with T12K; and cholesterol secretion strikingly increased with TCDC, with a
high cholesterol-phospholipid ratio. The estimated CMCs of TC, TCDC, and
T12K were 3.3, 0.7, and 6.2 mM respectively; the relative
lecithin-solubilizing capacities were 4.4:2.6:1. We conclude that the
micellar characteristics of the bile acids studied do not explain the
differences in water and lipid secretion observed, and that effects within
the hepatocyte may be equally important.
