The effects of
norcholate (a C23
bile acid that differs from
cholate in having a side chain containing four rather than five
carbon atoms) on bile flow and biliary
lipid secretion were compared with those of
cholate, using the anesthetized rat with a bile
fistula.
Norcholate and
cholate were infused intravenously over the range of 0.6-6.0 mumol X min-1 X kg-1. Both
bile acids were quantitatively secreted into bile;
norcholate was secreted predominantly in unconjugated form in contrast to
cholate, which was secreted predominantly as its
taurine or
glycine conjugates. The increase in bile flow per unit increase in
bile acid secretion induced by
norcholate infusion [17 +/- 3.2 (SD) microliters/mumol, n = 8] was much greater than that induced by
cholate infusion (8.6 +/- 0.9 microliters/mumol, n = 9) (P less than 0.001). Both
bile acids induced
phospholipid and
cholesterol secretion. For an increase in
bile acid secretion (above control values) of 1 mumol X min-1 X kg-1, the increases in
phospholipid secretion [0.052 +/- 0.024 (SD) mumol X min-1 X kg-1, n = 9] and
cholesterol secretion (0.0071 +/- 0.0033 mumol X min-1 X kg-1, n = 9) induced by
norcholate infusion were much less than those induced by
cholate infusion (0.197 +/- 0.05 mumol X min-1 X kg-1, n = 9, and 0.024 +/- 0.011 mumol X min-1 X kg-1, n = 9, respectively; P less than 0.001 for both
phospholipid and
cholesterol). The strikingly different effects of
norcholate on bile flow and biliary
lipid secretion were attributed mainly to its possessing a considerably higher critical micellar concentration than
cholate.