The effects of three epimeric trihydroxy-cholanoic
acids, cholic acid (C), 7 beta-hydroxy-(7 beta) and 12 beta-hydroxy-(12 beta) isocholic
acids on bile flow,
lipid secretion, bile synthesis and bile micellar properties were studied in the rat with a bile
fistula. The
bile salts were infused intraduodenally starting 72 hours after cannulation when endogeneous
bile salt synthesis had plateaued after the
bile salt pool was drained. The
bile salts were infused at two levels approximately 2 and 4 mumol min-1 kg-1. All three
bile salts were absorbed and secreted almost quantitatively into the bile.
Cholic acid was secreted in the conjugated form, 7 beta conjugated to approximately 60% and 12 beta completely in the unconjugated form. The
bile salts did not undergo any significant biotransformations during the one passage from the intestine through the liver. Bile flow increased from the preinfusion level for all three
bile salts infused in the order 7 beta greater than 12 beta greater than C. The bile flow increased linearly with
bile salt secretion more for 7 beta than for C and 12 beta. Infusion of C increased the secretion into bile of
phospholipid (PL) and
cholesterol (CH) over the preinfusion values. Infusion of 7 beta as well as 12 beta resulted in a parallel decrease in the secretion of PL as well as CH compared to the preinfusion values. The infusion of C and 7 beta at the two levels used decreased the secretion of newly synthesized
bile salt below the control level.(ABSTRACT TRUNCATED AT 250 WORDS)