Stimulation of bile and pancreatic secretion by duodenal perfusion with Na-taurocholate in the cat compared with jejunal and ileal perfusion

Role of bile acids in the control of pancreatic secretion and CCK release

In most species stimulated pancreatic enzyme secretion and CCK release are increased in the absence and inhibited in the presence of luminal bile acids. Changes in CCK release are almost unequivocal in all investigated species. With respect to enzyme secretion, physiological bile acid concentrations seem to be necessary to exert an inhibitory effect on stimulated enzyme output in humans. Bile acids administered in higher concentrations may enhance basal and stimulated pancreatic secretion. Furthermore, the chemical properties of different bile acids (i.e., hydroxylation, conjugation) seem to contribute to their stimulating effect on enzyme secretion as was observed in several species. The rank order of bile acids inhibiting stimulated enzyme secretion in humans is taurocholate greater than taurodeoxycholate greater than taurochenodeoxycholate. On the other hand, chenodeoxycholic acid exerts the strongest stimulating effect on secretion release, which may account for the stimulating effect of this bile acid on exocrine pancreatic secretion. The strongest candidate for the mediator role in bile-acid-induced changes of exocrine pancreatic secretion is CCK (at least in dogs and rats). The CCK cell may be influenced either directly or indirectly. In conclusion, bile acids modulate pancreatic enzyme secretion and CCK release. CCK is a major candidate for this regulatory role under physiological conditions.

Effect of intraduodenal bile and Na- taurodeoxycholate on exocrine pancreatic secretion and on plasma levels of secretin, pancreatic polypeptide, and gastrin in man

The effect of intraduodenally administered cattle bile (CB) and Na-taurodeoxycholate (TDC) on basal pancreatic secretion and plasma levels of secretin, pancreatic polypeptide (PP), and gastrin were investigated on two separate days in 10 fasting volunteers. Doses of 2-6 g CB and 200-600 mg TDC were given intraduodenally at 65-min intervals. Volume, bicarbonate, lipase, trypsin, amylase, and bilirubin were measured in 10-min fractions of duodenal juice, and GI peptides determined by radioimmunoassay. CB and TDC enhanced significantly and dose-dependently volume, bicarbonate and enzyme secretion, and plasma secretin and PP levels. In contrast, plasma gastrin showed only a marginal increase. We conclude that the hydrokinetic effect of intraduodenal CB and TDC is at least partially mediated by secretin. Gastrin could be ruled out as a mediator of the ecbolic effect, whereas other GI peptides, primarily CCK, and/or neural mechanisms must be considered possible mediators. Both pathways may also play a role in the PP release observed.

Pancreatic secretory response to intestinal stimulants: a review

In humans and many laboratory animals, protein digestion products such as peptides and amino acids and fat digestion products such as fatty acids and monoglycerides are potent intestinal stimulants of pancreatic enzyme secretion. The pancreatic enzyme response to these intestinal stimulants is related to the perfused load (amount per unit time) rather than to concentration. Both neural and hormonal pathways mediate the enzyme response to these intestinal stimulants. Enteropancreatic, cholinergic, vago-vagal reflexes are probably the most important mediators of the enzyme response to low loads of amino acids and fatty acids; hormones, such as cholecystokinin, seem to be the major mediators of the response to high loads of amino acids and fatty acids. Under physiological conditions it is probably the interplay of neural and hormonal mechanisms which regulates the pancreatic response to these stimulants. Gastric acid is the major regulator of postprandial pancreatic bicarbonate secretion. Secretion released by HCl is probably the most important physiological hormonal mediator of postprandial pancreatic bicarbonate secretion; its effect being potentiated by extrinsic (vagal) and intrinsic (intrapancreatic) cholinergic nerves and release of other hormones, such as cholecystokinin.

Na-taurodeoxycholate acts as a specific intestinal stimulus of exocrine pancreatic secretion in man

The effect of intraduodenally administered cattle bile, Na-taurodeoxycholate, and Na-taurocholate on secretin-stimulated exocrine pancreatic secretion was investigated on 40 fasting young healthy volunteers. Intraduodenal bile stimulated significantly and dose-dependently hydrokinetic and ecbolic pancreatic secretion. Only bile, but not secretin intravenously, both applied in a dosage equivalent with respect to their hydrokinetic action, caused a significant increase of enzyme output and enzyme concentration as well. Intraduodenal Na-taurodeoxycholate enhanced also dose-dependently secretin-stimulated volume, bicarbonate, and enzyme secretion. The effect was related to the load, not to the concentration of this bile salt. On the other side, Na-taurocholate had only a weak and not dose-dependent hydrokinetic and no ecbolic effect. It is concluded that not bile salts in general, but only certain of them--like Na-taurodeoxycholate--are the effective constituents of bile, acting as specific intraduodenal stimulants of hydrokinetic and ecbolic pancreatic secretion.

Bile-stimulated secretin release in cats

Duodenal perfusion with sodium taurocholate (TC), pH 10.5 (60 mM, made isotonic with NaCl, 30 ml/h for 90 min), increased the plasma immunoreactive secretin level (IRS) from 2.1 +/- 1.0 to 19.1 +/- 6.0 pM (p less than 0.025; n = 6) in anaesthetized cats. Dose-response studies with TC, pH 7.2 (0-60 mM, made isotonic with NaCl, 45 ml/h for 20 min), demonstrated a threshold concentration of TC for IRS release between 10 and 15 mM (p = 0.05; n = 6). Instillation of gallbladder bile from the same animal (1.5 +/- 0.1 ml, pH 7.0 +/- 0.1, over 12 min) increased the IRS concentration from 1.5 +/- 0.4 to 8.1 +/- 3.4 pM (p less than 0.025; n = 6). IRS concentrations also increased when gallbladder bile was mixed with either saline (from 3.4 +/- 1.7 to 11.6 +/- 2.5 pM; p less than 0.05; n = 5) or feline pure pancreatic juice (PPJ) (from 3.1 +/- 0.7 to 5.7 +/- 1.1 pM; p less than 0.025; n = 6). The peak value was significantly lower when bile was mixed with PPJ than with saline (p less than 0.05). We conclude that TC, the dominating bile salt in feline bile, can release IRS also above pH 7, that physiological concentrations of TC can elicit this response, that the response is also produced by gallbladder bile from the same animal, and that PPJ inhibits the bile-induced IRS release. Thus secretin release by bile is likely to be a physiological principle in the regulation of the pancreatic secretion.

Inhibition of pancreatic exocrine secretion and augmentation of the release of gut glucagon-like immunoreactive materials by intraileal administration of bile in the dog

The effect of intraileal instillation of bile, a stimulant of gut glucagon-like immunoreactive materials (gut GLI), on secretin-stimulated pancreatic secretion was examined in anesthetized dogs. Intraileal bile significantly inhibited the flow rate of secretin-stimulated pancreatic secretion. The inhibition of pancreatic secretion was accompanied by an elevation of plasma concentration of gut GLI. Taking the inhibitory effect of glucagon on pancreatic exocrine secretion into consideration, it could be reasonably postulated that gut GLI may be a mediator of bile-induced ileal inhibition of pancreatic exocrine function.

Effects of duodenal perfusion with sodium taurocholate on biliary and pancreatic secretion in man

The effects of intraluminal sodium taurocholate (STC) on biliary and pancreatic secretion were studied in man using a duodenal perfusion technique and indocyanine green (ICG) as an exogenous biliary marker. Duodenal perfusion with 15 or 30 mmol/l STC in healthy subjects markedly suppressed caerulein and secretin stimulated biliary indocyanine green (ICG) excretion in a dose responsive manner, i.e. to 40% (17-95%, +/- 2 SD, n = 5) (P less than 0.025) and 32% (26-38%, +/- 2 SD, n = 3) (P less than 0.003) of i.v. ICG infusion, respectively, with a maximum suppression to 26% and 10%, respectively. In cholecystectomized subjects (n = 5), significant changes in ICG excretion were not observed during STC (15 mmol/l) perfusion. There were no suppressive effects on pancreatic enzyme or bicarbonate secretion in any of the subjects. Our observations suggest that the bile salts STC in the duodenum in man activated a mechanism which selectively suppressed biliary excretion. This is probably due to relaxation of the gallbladder and an increase in gallbladder storage of bile.