Vasoactive intestinal polypeptide is a potent regulator of bile secretion from rat cholangiocytes  Won Kyoo Cho, James L. Boyer  Gastroenterology  Volume 117, Issue 2, Pages 420-428 (August 1999) DOI: 10.1053/gast.1999.0029900420

1 Fig. 1. Effect of VIP on total bile flow. One-pass portal perfusion of 100 nmol/L VIP (■; n = 6) with taurocholate supplementation at 1 μmol/min increased total bile flow by ~14% compared with the albumin (ALB) carrier control (♢; n = 6). Results are mean ± SEM. *P < 0.05. Gastroenterology 1999 117, 420-428DOI: (10.1053/gast.1999.0029900420)

2 Fig. 2. Effect of VIP on bile flow in IPRLs. Portal infusion of 100 nmol/L VIP with albumin carrier (■; n = 5) did not stimulate bile flow in normal rats (A) in the absence of bile salt infusion but produced a significant increase in secretion in livers perfused from 2-week bile duct–ligated rats (50-60 minutes) (B) compared with the previous baseline level (40-50 minutes). Secretion was unchanged in control bile duct–ligated rat livers (♢; n = 5) infused with albumin alone (mean ± SEM). *P < 0.05. Gastroenterology 1999 117, 420-428DOI: (10.1053/gast.1999.0029900420)

3 Fig. 3. Effect of VIP on bicarbonate output of bile in IPRLs. VIP (100 nmol/L; n = 5; ■) stimulated biliary bicarbonate output in (A) normal and (B) 2-week bile duct–ligated rats. In contrast, no significant changes in biliary bicarbonate output were seen in controls infused with albumin alone (♢; n = 5). Gastroenterology 1999 117, 420-428DOI: (10.1053/gast.1999.0029900420)

4 Fig. 4. Effect of liver weight in VIP-stimulated choleresis in 2-week bile duct–ligated rat livers. The relative percent of peak and baseline values of bile flow, [HCO3−] and HCO3− output are plotted as a function of liver weight. The curves are fitted with nonlinear regression and show a highly significant positive exponential correlation of liver weights with relative percent of peak and baseline values of bile flow, [HCO3−] and HCO3− output values. Gastroenterology 1999 117, 420-428DOI: (10.1053/gast.1999.0029900420)

5 Fig. 5. Effect of VIP (■;100 nmol/L; n = 5) on luminal area in isolated hepatocyte couplets. Albumin infusions alone (♢; n = 11) or with VIP (100 nmol/L) or glucagon (○; 100 nmol/L; n = 9) were started at time 0, and the luminal area of the couplet was measured at 2-minute intervals (mean ± SEM). VIP (100 nmol/L) produced no significant changes in luminal area compared with the albumin control, whereas glucagon (100 nmol/L) increased luminal area by ~50% in 20 minutes. Gastroenterology 1999 117, 420-428DOI: (10.1053/gast.1999.0029900420)

6 Fig. 6. Time course of VIP (■; 100 nmol/L; n = 9)-stimulated secretory response in IBDU and VIP dose-response curve. (A) The lumens of IBDUs expanded after infusion of VIP by ~100% in 30 minutes compared with the albumin controls (♢; n = 7), which decreased by about 5% (mean ± SEM). (B) The lumens of IBDUs expanded by 35% after 30 minutes of stimulation with 1 nmol/L VIP and by ~100% with 100 nmol/L VIP (mean ± SEM). *P < 0.001. Gastroenterology 1999 117, 420-428DOI: (10.1053/gast.1999.0029900420)

7 Fig. 7. Comparison of secretory response to VIP (100 nmol/L) in IBDUs with other neuroendocrine peptides. Stimulation of IBDUs with equimolar amount (100 nmol/L) of bombesin or secretin induced increases in luminal area by ~40% and ~60%, respectively, compared with ~100% for VIP. *P < 0.01. Gastroenterology 1999 117, 420-428DOI: (10.1053/gast.1999.0029900420)

8 Fig. 8. Effect of a specific VIP inhibitor on VIP (100 nmol/L) secretory response in IBDU. VIP (100 nmol/L) infusion was started at time 0. Albumin alone or VIP receptor inhibitor (VI) (2 μmol/L) was infused for 35 minutes via a separate syringe pump starting 5 minutes before the VIP infusion. VIP inhibitor significantly inhibited the VIP-stimulated secretory responses in IBDU. After stopping the infusion, this inhibition was promptly reversed, as reflected by the change in the slope of increase. *P < 0.001. Gastroenterology 1999 117, 420-428DOI: (10.1053/gast.1999.0029900420)

9 Fig. 9. Effect of VIP (0.1-1000 nmol/L) and secretin (100 nmol/L) on cAMP levels in cholangiocytes. Stimulating cholangiocytes with 100 nmol/L VIP for (A) a different incubation time (0-30 minutes) or different VIP dose (0.1-1000 nmol/L) for 15 minutes had no effect on intracellular cAMP levels, whereas (B) secretin (100 nmol/L) and IBMX (50 μmol/L) increased the cAMP levels 22.5-fold. BDC, bile duct cells. Gastroenterology 1999 117, 420-428DOI: (10.1053/gast.1999.0029900420)