ENHANCING EFFECTS OF VASOCONSTRICTORS ON BILE-FLOW AND BILE-ACID EXCRETION IN THE ISOLATED-PERFUSED RAT-LIVER

The effects of vasoconstrictors on bile flow and bile acid excretion w ere examined in single-pass isolated perfused rat livers. Administrati on of norepinephrine (NE), 4 nmol/min, plus continuous infusion of tau rocholate (TC) (1.0 mu mol/min) rapidly increased bile flow in 1 min, and from min 5 until the end of NE administration (late period) bile f low remained above the basal level (111.7 +/- 2.2%), as did bile acid output (114.6 +/- 1.8%). Without TC infusion, administration of NE pro duced no increase in the late period. Administration of NE plus tauroc henodeoxycholate (1.0 mu mol/min) increased bile flow and bile acid ou tput in the late period to 121.9 +/- 7.0 and 137.1 +/- 6.8%, respectiv ely. With NE plus taurodehydrocholate, the respective values were only 105.4 +/- 1.6 and 104.1 +/- 4.0%. When horseradish peroxidase (HRP) ( 25 mg) was infused over 1 min with continuous NE, the late peak (20-25 min) of HRP elimination into bile significantly exceeded that of untr eated controls (P < 0.01). These observations suggest that vasoconstri ctors enhance biliary excretion of more hydrophobic bile acids, in par t by stimulating vesicular transport.