Products Pancreatic and Gallbladder...
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Interactions between Intraluminal Bile Acids and Digestive
Products on Pancreatic and Gallbladder Function
JuAN R. MALAGELADA, VAY L. W. Go, EUGENE P. DIMAGNO, andW. H. J. SUMMERSKILL
From the Gastroenterology Unit, Mayo Clinic and Mayo Foundation,Rochester, Minnesota 55901
A B S T R A C T Interactions between bile acids (tauro-cholate, TC; taurochenodeoxycholate, TCDC; or tauro-deoxycholate, TDC) and digestive products (essentialamino acids, EAA or monoolein, M1O) in the lumen ofthe proximal small bowel, affecting pancreatic enzymesecretion and gallbladder contraction, were studied in 77healthy volunteers by a perfusion imetlhod. Perfusion ofEAA or MO caused significant increases in pancreaticenzyme output together with gallbladder contraction;MO was more potent and induced enzyme outputs com-parable to the maximal response attained witlh intra-venous clholecvstokinin -panicreozvminl (CCK-PZ). Per-fusion of TC alone had no effect, but addition of 10mM of either TC, TCDC, or TDC to perfusates con-taining EAA, or 10 nm-M TC to MO, or both significantlyreduced pancreatic enzyme output and prevented gall-bladder contraction. A lower concentration of TC (5mM) added to EAA also produced a significant inhibi-tory effect. Inhibition of the stimulatory action of di-gestive products occurred in the jejunum as well as inthe duodentum. The inhibitory action of bile acid wasconsidered to be intralutlminal since (a) bile acid did notmodify the effects of ( CK-PZ given intravenously; and(b) the stimulatory effect of digestive products perfusedin the duodenum on pancreatic and gallbladder functionwas not influenced by- simultaneous perfusion of bileacid in the jejunumn.
It is proposed that this inhibitory- effect of bile acidis mediated through inhibition of CCK-PZ secretion byhigh intraluminal concentrations of bile acid. Inlhibitionof CCK-PZ secretion by bile acid mav contribute to theregulation of pancreatic and gallbladder functioin during
Part of this work was presented at the Meeting of theAmerican Society for Clinical Investigation, Atlantic City,N. J. 1972. J. Clin. Invest. 51: 59a. (Abstr.).Received for publication 9 Oc-tobcr 1972 anid i7t rcv'ised
formz 14 April 1973.
digestion by reducing pancreatic enzyme secretion andpermitting the gallbladder to refill after evacuation ofits coiltenits.
Certain products of digestive hydrolvsis of nutrieints inthe lumen of the proximal small bowel provide the majorstimulus for secretion of pancreatic enzymes and gall-bladder contractioni (1), thought to be mle(liatedI by re-lease of cliolecvstokinin-pancreozv-mini (CCK-PZ ) 1 fromthe mucosa of the upper small intestine. The potency of-ariouis aimiino acids, mlicellar fatty acids, and dextrosefor stinmulatioin of pancreatic and biliarv function differin m11aln (2). In animals, fatty aci(ds also stimulate pan-creatic enzvme secretion and gallbladder contraction (3).The effects of combinations of these compounds, nor-nmally present together wN-ith secretions in the snmall in-testine after meals, have not beein investigated. The pres-ent study, enmploying a perfusion technique for measur-inig total pancreatic einzyme anid biliary outputs in re-spIonse to duodenal perfusion of different stimluli (2, 4),lhas tlhree major aims. First, to comIlpare the effects ofessential amino acids (EAA) and monoolein (MO)separately and together on pancreatic enzyme outputand gallbladder emptying. Second, to determiiine the in-traluminal role of bile acids alone or in combinationwith EAA or MIO or both on pancreatic secretion andgallbladder contraction. And, third, to define certainicharacteristics of the actions of bile acids on the re-sponse to EAA or M1O.
'Abbreviationts utsed it this paper: CCK-PZ, cholecysto-kinin-pancreozymin; EAA, essential amino acids; .ME,emulsified monoolein; MIO, monoolein; PEG, polyethyleneglycol; TC, taurocholate: TCDC, taurochenodeoxycholate;TDC, taurodeoxycholate.
The Journal of Clinical Investigation Voluime 52 September 1973*2160-21652160
TABLE IComposition of the Perfusates and Outputs of Pancreatic Enzymes and Bilirubin
Enzyme output (meanSE)
Perfusate Amount Perfusions Trypsin Lipase Bilirubin output (mean =SE)
mAI number kU/h mg/hNormal saline (control) 150 8 5.7t1.6 26.844.2 5.5-1.1Sodium TC 10 5 7.30.3 28.93.8 1.340.8EAA 78Alone 18 22.32.1 98.14 12.3 24.32.3In combination with
TC 5 5 13.31.7 72.88.6 5.5 1.6TC 10 10 6.90.8 38.67.2 2.41.9Sodium TDC 10 4 11.61.9 54.113.2 6.41.3Sodium TCDC 10 5 10.82.7 56.7 11.4 4.82.0
Stabilized with 1 mM TC (ME) 5 38.2 3.6 179.4416.7 28.65.5In combination with
TC 10 8 10.60.6 48.72.7 6.71.4EAA 4 40.1-4.3 216.528.2EAA + TC (10 mMI) 5 12.33.7 58.3 16.1
CCK-PZ (i.v.)W\ith normal saline (control) 5 41.31.8 205.932.0In combination with EAA + MO + TC
(10 mM) 5 39.94.4 152.030.6 37.68.2Iintrajejunal EAA 78
Alone 8 17.142.8 89.421.8 33.09.7With TC 10 4 4.70.8 32.4t6.9 4.00.4
METHODS77 healthy male volunteers (aged 21-52) participated in thestudies. After an overnight fast, a two-lumen polyethylenetube was placed intraduodenally under fluoroscopic con-trol. Isotonic saline or test solutions containing a non-absorbable marker polyethylene glycol (PEG) 5 g/literwere infused into the second part of the duodenum at aconstant rate (10 ml/min). Specimens of duodenal contentsduring steady-state conditions were drained by siphonage fromthe area of the ligament of Treitz, 20 cm distal to the infu-sion site. Perfusates were collected over ice and pooled at20-min intervals. Gastric juice was continuously aspiratedfrom the antrum by an additional tube. In each study, iso-tonic saline was perfused initially for cleansing for 60 minand was followed by perfusion for 100 min of either a con-trol (isotonic saline) or test solution containing EAA orMO alone or in combination with different bile acids, com-prising sodium taurocholate (TC), sodium taurocheno-deoxycholate (TCDC), or sodium taurodeoxycholate (TDC)(Table I).Volume, pH and PEG concentrations (5) were measured
in gastric and duodenal aspirates. Duodenal trypsin, lipase,bilirubin, and bile acid concentrations were also determinedby methods previously described (4, 6) and outputs of thesesubstances were calculated from their concentrations induodenal samples relative to PEG. Since perfusion of di-
gestive products causes an initial, but nonspecific, higheroutput of pancreatic enzymes consistent with a "washouteffect" (2), only aspirates collected after the first 40 minof perfusion were considered representative of the effect ofluminal stimuli on pancreatic enzyme output (Table I).Luminal bile acid concentrations (quoted in the text) arethose found during this period. By contrast, gallbladder con-traction generally occurred during the first few minutes ofperfusion of a stimulus and was determined from "peak"bilirubin output per hour. This value was derived from thehighest bilirubin output in any 20-min period added to thebilirubin outputs in the two adjacent 20-min periods (Table I).The composition of the perfusates is tabulated (Table I).
Essential amino acids (2) were obtained from AldrichChemical Co., Inc., Milwaukee, Wis. Sodium TC, sodiumTCDC, and sodium TDC were synthesized from taurine(Eastman Organic Chemicals Div. Eastman Kodak Co.,Rochester, N. Y.) and cholic acid, chenodeoxycholic acid, anddeoxycholic acid, respectively (Matheson Coleman, & Bell,East Rutherford, N. J.) as described by Hofmann (7). Theproducts migrated as single spots on thin-layer chromatog-raphy. Emulsified monoolein (ME) consisted of 10 mM of1-monoolein (Eastman Organic Chemicals Div.) in dilute 1mM sodium TC. This solution was sonicated for 60 minusing a Biosonik (Will Scientific, Inc., Rochester, N. Y.)to emulsify the MO into solution. The preparation was found
Effect of Bile Acid on Pancreatic and Biliary Secretions 2161
Essentiat amino acid perfusion
i I MeanSEIS
to 1% Bilirubin
1\1'.++i++++ ++--++-20 20 80
0160 240 320
FIGURE 1 Trypsin and bilirubin outputs during continuousintraduodenal perfusion of EAA (four studies).
to be greater than 95%o monoglyceride by thin-layer chro-matography and recoveries from the perfusates showed thatthe monoglyceride had been more than 90%c hydrolyzed tofatty acid during the study. When EAA, MO, or bile acidswere combined in test solutions, the originial molar con-centrations were preserved. All perfusates were preparedimmediately before use, made isotonic with sodium chloride,adjusted to pH 6.3 and warmed to 37C.The effects of the various test solutions on pancreatic en-
zyme secretion and gallbladder contraction were comparedlwith those obtained with intravenous CCK-PZ (Batch#22927, supplied by Professor E. Jorpes, Karolinska In-stitutet, Stockholm, Sweden) given to 10 subjects for 60min at a dose of 0.250 Crick Harper Raper U/kg/min dur-ing intraduodenal perfusion of isotonic saline (five studies)or the combination of EAA, MO, and TC (five studies).This dose of i.v. CCK-PZ produced "maximal" pancreaticenzyme output of a similar magnitude to those reported here(8). CCK-PZ given at this high dose quickly produces asteady pancreatic enzyme output which makes it unnecessary
Normra .saine E, se r! ir'7o
FIGURE 2 Trypsin anid bilirubin output during continuousintraduodenal perfusion of EAA during and after additionof 10 mM sodium TC (four studies).
to risk side effects by prolonging the infusion for more than60 min.2To characterize the effect of TC on pancreatic and biliary
responses to EAA, we performed additional studies. Eachwas carried out on differenit volunteers and consisted of oneor several sequential perfusions: (a) to establish the profileof pancreatic anid biliary secretory responses to prolongedstimulation with EAA, EAA was perfused intraduodenallyover a period of 5 h (four studies) after the initial 1-h per-fusion of isotonlic saline (Fig. 1); (b) to determine thereversibility of the effect of TC on the response to EAA,10 mM TC was added during the first 100 mnil (Fig. 2) orduring the second 100 min (Fig. 3) of a 5-h EAA perfusionstudy (four studies each); (c) to determine the effect ofTC on the response to EAA in the jejunum, EAA aloine(eight studies) or EAA plus TC (four studies) was per-fused for 100 min, 30 cIIm distal to the ligament of Treitz,while normal saline was perfused in the duodenum; andfinally, (d) to further establish whether the site of actionof TC was local or systemic, EAA was perfused alonie in-traduodenally for 100 min and then combined with TC foran additional 100 min. During the third 100-miml period,TC wvas substituted for the saline perfusion 30 cm beyondthe ligament of Treitz (four studies). Pheniol red was adde(dto all jejunal perfusates as a mrlarker to monitor proximiialreflux into the duodenal segment, but none occurredl.The validity and reproducibility of the perfusion teclmiiique,
coefficients of variation of the chemical determinatioils, andcalibration of measurements of enzyme activity have beendetailed elsewhere (2, 4). Pancreatic enzyme secretion wasexpressed in kilo units (Interniational Units X 103). Es-sential preliminary in vitro studies showed that bile acidsadded to intestinal juice do not modify pancreatic enizymeactivity.2
Effects of bile acids anld digestive products oni panicr-e-atic en.zIymne and bilirubin outputs (Table I). A signifi-cant increase in pancreatic trypsin anid lipase outputsover basal values occurred durinig perfusionls witlh EAA(P < 0.01), ME (P < 0.01 ) or i.v. CCK-PZ (P