Biliary motility associated with gallbladder storage and duodenal delivery of canine hepatic biliary output

GASTROENTEROLOGY

1988;95:1069-80

Biliary Motility Associated With Gallbladder Storage and Duodenal Delivery of Canine Hepatic Biliary Output R. B. SCOTT

and S. C. DIAMANT

Department of Pediatrics Alberta, Canada

and Gastroenterology

Hepatic biliary output may be stored in the gallbladder (GB) or delivered into the duodenum. The role of the GB and sphincter of Oddi (SO) in the partition of hepatic biliary output between GB and duodenum was studied in 6 dogs during the interdigestive and postprandial periods. Three animals received a continuous intravenous infusion of [14C]taurocholic acid, which served as a marker of the steady-state hepatic output of radiolabeled bile acid. Gallbladder filling and emptying and duodenal delivery of [‘4C]taurocholic acid were determined using duodenal marker perfusion to measure output. Sphincter of Oddi, common duct, GB, and duodenal manometry was performed in 3 additional dogs. During fasting, partial GB emptying and an increased rate of duodenal delivery occurred between 60% and 90% of each cycle of the migrating motor complex. The majority of hepatic taurocholic acid output was stored in the GB during the first half of the migrating myoelectric complex. However, in the latter half of the migrating myoelectric complex, the frequency of SO contractions and basal SO pressure decreased, GB pressure increased, net partial GB emptying occurred, and peak rates of duodenal taurocholic acid delivery were achieved. Feeding induced immediate decreases in basal SO pressure and frequency of phasic contractions, and an immediate increase of GB pressure. Gallbladder emptying and duodenal taurocholic acid delivery were maximal in the first 10 min after feeding. Thus, both the cyclic interdigestive and immediate postprandial increases in duodenal bile acid delivery are associated with SO relaxation and GB contraction. The immediate postprandial changes in SO and GB motility, and in duodenal bile acid output, suggest a cephalic phase of postprandial duodenal bile acid delivery.

H and

epatic bile may be stored in the gallbladder (GB) or delivered into the duodenum (1). Gallbladder sphincter of Oddi (SO) motor function deter-

Research

Group.

IJniversity

of Calgary.

(:algc~ry,

mine how hepatic output is partitioned; however, the specific roles of GB and particularly SO motor function in the regulation of interdigestive and postprandial duodenal bile acid delivery remain controversial. This is due in part to interspecies differences in SO anatomy (2), function (3), and control mechanisms (4,s). However, the anatomy of the SO (2), the motility of SO (3,6) and GB (7-10). the pattern of fasting or fed intestinal motor activity (11,12), and the pattern of duodenal bile acid delivery (7,13-15) are similar in dogs and humans. The present stud] was performed in a conscious canine animal model during the interdigestive and postprandial periods to (a) determine the pattern of partition of hepatic biliary output between GB and duodenum and (b) characterize GB, common duct, and SO pressure dynamics and motility. Concurrent continuous measurement of GB, common duct, and SO manometric pressures can be considered together with data on bile partition to demonstrate how GB and SO motor activity contribute to the development of pressure gradients that determine the partition of hepatic: biliary output during the interdigestive and postprandial periods.

Materials Animal

and Methods

Prepuration

Six healthy mongrel dogs weighing 18-26 kg were used. The experimental protocol received ethical approval from the Animal Care Committee of the University of Calgary. Anesthesia was induced with thiopental sodium (IO mgikg i.v.) and was maintained with halothane. LJnder sterile conditions the following surgical procedures were

Abbreviations used in this paper: GB, gallbladder; MMC, migrating myoelectric complex: SO, sphincter of Oddi; TCA, taurocholic acid. ( 1988 by the American Gastroenterological Association 0016-5085188/$3.50

1070 SCOTT AND DIAMANT

performed: (a) a modified Thomas duodenal cannula was inserted in all 6 animals to permit visualization of the papilla of Vater and cannulation of the common bile duct, or duodenal intubation; and (b) in 3 animals a polyethylene catheter (PE-190; ID, 1.19 mm) was secured in the GB fundus with a purse-string suture, and the other end was brought out to a second cannula in the abdominal wall. Between experiments both cannulas were closed with corks. Animals were given intravenods fluids for the first 48 h postoperatively and were gradually advanced to a standard diet and water ad libitum. Experimental

Design

After a l-wk postsurgical recovery period, dogs were studied when they were conscious and unrestrained after an la-h fast. In each experiment a triple-lumen polyvinyl chloride manometry catheter, constructed by fusing three catheters (ID, 0.75 mm; OD, 1.45 mm) with tetrahydrofuran and with orifices 5 cm apart, was passed through the duodenal cannula. Duodenal motility was recorded during one complete cycle of the migrating myoelectric complex (MMC) and 20 min of the next cycle. Animals were fed at this point, and the recording was continued for 60 min after feeding. Experiments in the 3 animals with a duodenal cannula alone (protocol 1) were designed to determine the pattern of partition of hepatic biliary output between GB storage and duodenal delivery, and experiments in the 3 animals with both duodenal and GB cannulas (protocol 2) were designed to measure the pressure dynamics of SO, common duct, and GB. Protocol 1: partition of hepatic biliary output. Twenty-four 6-6-h experiments were performed in 3 dogs. Animals received a continuous intravenous (iv.) infusion of [14C]taurocholic acid (TCA), which served as a marker of the steady-state hepatic output of radiolabeled bile acid. A solution containing 25 pmoliml TCA (CalbiochemBehring, La Jolla, Calif.) labeled with 3 &i of [14C]TCA (New England Nuclear, Boston, Mass.) and 154 mM sodium chloride was infused intravenously by a peristaltic pump (Perpex pump, LKB Producter, Sweden) at a constant rate of 1.6 mlimin. Delivery of [14C]TCA into the duodenum was measured indirectly with a nonabsorbable duodenal marker perfusion technique (16 experiments), or directly by cannulating the common bile duct (a experiments). The former was a measure of duodenal delivery with SO function intact; the latter was a measure of delivery with SO excluded and replaced by a constantoutput resistance to flow (13). A standard marker perfusion system (16) was used to quantitate the output of bile acids into the duodenum. The intestine was intubated through the duodenal cannula with a triple-lumen polyvinyl chloride tube. The proximal orifice was positioned by direct inspection at the level of the SO, the collecting orifice 10 cm distally. The third lumen, with its opening adjacent to the second, functioned as a vent to prevent occlusion of the aspiration orifice by 1% polyethylene mucosa. A nonabsorbable, water-soluble, glycol (PEG) 4000 solution with 5 &i of [3H]PEG 4000 [New England Nuclear) and 154 mM sodium chloride was infused through the proximal orifice by a peristaltic pump

GASTROENTEROLOCY Vol. 95,No. 4

(Perpex pump, LKB Producter) at a constant rate of 1.6 ml/min. Transit time through the mixing segment and aspiration tubing was <3 min in each phase of the MMC (13). A minimum of 30 min (62 * 11 min; range, 30-172 min) was allowed for equilibration of the i.v. and duodenal infusions. Then, successive lo-min collections of duodenal aspirates were continued until 30 min after stopping the i.v. infusion. Cannulation of the common duct for direct measurement of duodenal delivery was performed under direct visualization. Output resistance was set at 0 by adjusting the height of the draining tip of the catheter relative to the papilla of Vater and taking the resistance to flow through the catheter into consideration (13). A minimum of 30 min (95 + 22 min; range, 41-243 min) was allowed for equilibration of the i.v. infusion before collecting successive lo-min samples of bile. The dead space of the collection tube was only 0.5 ml. The sample collection period of 10 min ensured that even during periods of low flow, samples remained representative of duodenal bile acid delivery despite the additionally interposed dead space. Leakage of bile acids around the catheter averaged
BILIAKY

lnterdigestiie Period

MOTILITY

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Postprandial Period

k’igurr~ I. (Condensed record of duodenal (III. D,). SO. c.ommon duct (CD). and Cl3 motility in the interdigestive and postprandial periods. Traces I, 3. and 4 rewrd GB, common duct, and SO pressure. respectively. and traces 6 and 7 record intraduodenal pressure at the lwel of the SO and 10 cm distally in the duodenum. The second trace is of the integrated or c:umrllative area under the GH pressure tracing lvith respect to time (I P(t)dt). Similarly. tracing 5 records the integrated or curnulativ~~ area under the SO pwssurtt trar ing with respect to time. Traces 2 and ?I automaticall\~ reset every 3840 mmHg s. Thr slop: ot the tracings in ~hanllels 2 ant1 5 is an average of the integrated basal and phask. variatioo in pressure over that timr, intc:rval.

diameter of the double-lumen catheter was 1.5 mm. The duodenal, SO. common duct, and GB manometry catheters were infused with Lvater at 0.5 mlimin using a minimally compliant pneurnohydraulic: capillary infusion system (Mui Scientific, Missisauga. Ontario, Canada). During infusion, the pressure required to overcome catheter resistance plus the hydrostatic pressure generated by placing the catheter orifices level with the animals’ SO was set at O. Abrupt occlusion of the catheter recording orifices gave a pressure rise of Z-e’ LOO mmHg/s. Using a slow-station pull-through technique. a pressure profile of the choledochoduodenal junction was obtained and the catheter was positioned and fixed so that the distal orifice was within the common duct and the proximal orifice within the SO. There was no demonstrable difference between the SO motility recorded using the 1.5mm-diameter catheter and a smaller single-lumen catheter with an outer diameter of 0.97 mm 13). Pressures were monitored using pressure transducers (motlel 128OC: Hewlett-Packard. Palo Alto, Calif.) and pressure amplifiers [model 8805D. HewlettPackard). The waveforms of SO and GB pressure that were output by the pressure amplifiers were directed to integrating amplifiers (model 8815A. Hewlett-Packard). The pressure tracirlgs from duodenum. SO, common duct. and GB. plus the c.umulative areas under the SO and GB pressure waveforms (Jf’(t]dt) M’ere recorded on a direct lvriting chart recorder (model i’758B. Hewlett-Packard) and an FM instrurnc~nt;ltion tape recorder (model 8868A. HewlettI’ack~~rtl!

Sample

Analysis

each experiment in protocol 1 aliquots of (a) the 1% PEG solution labeled with [,‘H]PEG. (b) the sodium TCA solution labeled with [‘“Clsodium TCA, and (c) each of the lo-min collections obtained by marker perfusion or direct collection were added to separate Is-ml volumes of Multisol (Isolabs, Akron, Ohio) and counted in a liquid scintillation counter (model LS9800; Beckman Instruments. Fullerton, Calif.) and the disintegrations per minute of “H and “C were determined using an internal standard and quench correction factor. The concentration of ‘“C micromole equivalents of TCA (subsequently called “C microcmoles) in any sample was equal to ‘“C disintegrations per minute per milliliter of the sample divided by the specific activity of “C in the i.v. infusate. This method of determining bile acid delivery obviates the influence of the enterohepatic circulation of endogenous bile acids on the specific activity of duodenal bile acids. Sufficient time elapsed between experiments that there was a negligible increase in counts above background for samples obtained before isotope infusion in successive experiments. In each experiment all sample counts were corrected for the background level obtained before i.v. infusion of isotope was commenced. During duodenal marker perfusion the rate of delivery into the duodenum of 14C micromoles was calculated for each 10.min interval: In

1072 SCOTT AND DIAMANT

where DO is the duodenal output, [Solute] is the solute concentration; i indicates infusate; and a indicates aspirate. With the SO cannulated, bile was collected directly so that the rate of delivery of 14C micromoles for each lo-min interval was determined directly from the volume of concentration. Data

Computation

Taped records of duodenal motor activity were played back at 16 times the recording speed and rerecorded on a pen chart recorder to yield a time-condensed recording from which the features of the MMC and fed motor pattern could be recognized by visual inspection, and to provide a time base against which duodenal delivery of 14C micromoles, GB filling and emptying, or biliary motility could be plotted. Migrating myoelectric complexes were recognized as cyclically recurring periods of intense regular contractile activity that migrated in an aboral direction through the duodenum. The period of intense contractile activity (phase III) was preceded by a period of irregular contractile activity (phase II) and followed by a phase of absent contractile activity (phase I). The end of phase III is easily identified and was chosen as a reference point. The time between the end of duodenal phase III activity of successive cycles was defined as the cycle period. Fed motor activity was characterized by the immediate cessation of the MMC and initiation of a continuous irregular pattern of contractions immediately after feeding. In protocol 1,the filling or emptying of the GB with 14C micromoles was calculated as the algebraic difference between the steady-state rate of hepatic bile acid secretion (equal to the continuous i.v. rate of infusion of [14C]TCA micromoles) and the rate of delivery of 14C micromoles into the duodenum during that interval (13). The quantity of 14C micromoles sequestered in the GB increases with time and may also vary depending on whether the experiment commences in a phase of GB filling or partial emptying. To correct for this variation we have assumed that 14C micromoles are evenly dispersed into any compartment into which they are delivered, and normalized all data on duodenal delivery and GB filling or emptying by expressing it as a percentage of the total amount available for duodenal delivery and GB storage or emptying, respectively (13). In each experiment the percentage of delivery into the duodenum and the percentage stored in the GB were calculated for the cycle period of the MMC and the first 4%min interval after feeding. For the lo-min sample interval during which duodenal delivery of 14C micromoles was greatest in each MMC, and in the 40 min after feeding, delivery was also expressed as a multiple of the steady-state rate of hepatic secretion, and the amount by which duodenal delivery of 14C micromoles exceeded the steady-state rate of hepatic secretion was expressed as a percentage of GB emptying. In protocol 2, minimum basal SO pressure, frequency and maximal amplitude of SO phasic contractions, and end-expiratory and inspiratory common duct pressures were determined by direct inspection of original records.

CASTROENTEROLOGY

Vol. 95, No. 4

Measurements were obtained for successive lo-min intervals, except at mealtime when they were also made for the 2-min interval before and after onset of feeding. Integrated average SO and GB pressures were determined for each of these intervals by dividing the integrated or cumulative area under the pressure waveform (in millimeters of mercury times seconds) by the duration of the interval (in seconds). For every experiment duodenal delivery of “C micromoles (protocol l),or minimum basal SO pressure, frequency and maximal amplitude of phasic SO contractions, integrated average SO pressure, lowest end-expiratory and highest inspiratory common duct pressure, and integrated average GB pressure [protocol 2), were plotted in relationship to the duodenal motility recording at the midpoint of the appropriate bile collection or pressure monitoring interval, respectively. To combine data on rates of delivery, pressures, or contraction frequency for all MMCs in each dog, the cycle period of each MMC was considered to be a standard time base of 100% length. To combine similar data for the 20 min before and 60 min after feeding for all experiments in each dog a real-time base was used. In each case the midpoints of each collection or pressure monitoring interval were plotted as either a percentile location on the standard time base during the MMC or as a real-time location in the 20 min before and 60 min after feeding. The magnitude of duodenal bile acid delivery (micromole equivalents per minute), pressure (millimeters of mercury), or frequency of contractions [number per minute) was plotted on the vertical axis at the midpoint of the appropriate interval. The curve obtained was interpolated using the method of linear interpolation at 5% intervals during the MMC, at 15, 5, and 1 min before feeding, and 1, 5, 15, 25, 35, 45, and 55 min after feeding. For each parameter in each protocol a mean was determined for each dog separately of the values obtained at each interpolation point in multiple experiments. The mean value obtained at each interpolation point for each of 3 dogs was then averaged and plotted to yield a composite curve (mean of the means of 3 dogs).

Statistical

Analysis

A two-way analysis of variance was employed (20) to determine whether, for a specific parameter, there was a significant difference in (a) the values at the peak (highest) and trough (lowest) levels of the composite curve during the MMC cycle period, (b) the values during equivalent intervals, e.g., the first half compared with the second half of the MMC cycle period or an interval just before and after feeding, or (c) the values obtained with SO intact or cannulated. There were two grouping factors: treatment and dog. Each analysis employed two treatments-(a) the elapsed percentage of MMC cycle period at which mean peak and trough values occurred, (b) the interval before and after feeding, or (c) the value obtained with SO intact or cannulated-and 3 animals. Data are expressed as mean * SE of the means of 3 dogs.

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Results Protocol

Interdigestive Period

Postprandial Period 100

1

Partition of hepatic biliary output with sphincter of Oddi function intact. Figure 2 (upper panel) shows the rate of duodenal delivery of ‘“C micromoles with SO function intact during the interdigestive and postprandial periods. During fasting, duodenal delivery maintained a low rate of 6 (I 5% of hepatic output) for the first half of pmolimin the cycle period of the duodenal MMC, but consistently increased to peak levels exceeding the steadystate rate of hepatic output before phase III of the MMC. The hatched area in the graph of Figure 2, where delivery rate exceeds the hepatic secretory rate, represents net partial GB emptying. The number of ‘“C micromoles delivered into the duodenum during the first half of the MMC (370 ? 260) was significantly different (p < 0.01)than that delivered during the second half of the MMC (1848 +- 720). Only 27.7% ? 8.2% of the total 14C micromoles available for delivery during the cycle period of the MMC were delivered into the duodenum. Thus, although the GB stored bile in the first half of the MMC and emptied bile during the second half of the MMC, the net function of the GB during fasting was to store or scqucster bile acids. Gallbladder emptying in the lo-mill interval during which the rate of duodenal I1’C]TCA delivery was maximal averaged 9.4:1, +- 5.1’>1,, and the rate of duodenal delivery during this interval was 2.1 * 0.6 times the steadystate rate of hepatic secretion. After feeding there was always an immediate release of bile pigment into the duodenum and the recovery of’ “C micromoles from the duodenum was consistently greatest in the first of the four lo-min collection periods (854 -t266, 276 ? 57, 523 t 136, vs.522 + 185.respectively; p < 0.05).Subsequently, rates of dclivery decreased but remained at levels indicative of continued GB emptying. It was not always possible to accurately measure duodenal bile 40 min after feeding because acid deli\rcry beyond emptying of food particles from the stomach led to intermittent obstruction of the aspiration port in the marker perfusion catheter. Data were available for all experiments for the first 40 min after feeding, and of the total “C micromoles alrailable for delivery 29.9% i- 6.3% were delivered into the duodenum. Gallbladder emptying in the first 10 min postprandially, when duodenal bile delivery was maximal, averaged lo.o?;,2 4.5(g), and the maximum rate of delivery during this interval was 2.3 t 0.6 times the steadystate rate of hepatic secretion. Ptrrtition of hepafic biliary output ivith sphincter oj’ Oddi cunnuloted. The rate of duodenal dclivcr!, of ‘“C mic:romolos with SO function ex-

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100 80 60

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Figure

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LrppPr pnnrl: duodenal delivery of 1“(:]?‘(:A in micromoles per minute during the illterdigestive period (fell) and in the postprandial period (right). with SO function intact. Unshed line indicates the steady-state rate of hepatic: [‘%]TCA output. il~tchrtl ureu. where the duodenal delivery rate rxc.et:ds the hepatic secretory rate, represents net partial C;H emptying. Maximum duodenal bile acid delivery occ.urrr:d before phase II1 of the LIMC in the interdigestive period dnd in the first lo-min inter\fal after feeding. I.cwr~r panel: duodenal per minute during deliver!; of [ “‘C]TCA in micromoles the interdigestive period (Ip\f) and in the postprandial period (right), with SO func lion exc.lutled try c.annul+ tion. Outflow resistancr: ICUS 0. IIuodr:nal tleliverv iiv creases to t:xc:eed the rate of hrpatic. nutput before: phaw III of the MMC. as bvith S(‘I function intac.t. However, in the postprandial period exclusion of SO function by cannulation results in rl del,iy of peal\ pclstprandial bile aLid tlrliver~ Ilntil 20-30 min after feeding.

eluded by cannulation (Figure 2, lower panel) approximated a value of 20 pmolimin (50’$, of the steady-state rate of hepatic output) during the first half of the cycle period of the MMC. Just as with SO function intact, it increased to peak levels exceeding the steady-state rate of hepatic output before phase III of the MMC. Duodenal delivery of “C micromoles during the MMC was greater with SO cannulated (44.5% 2 4.9%))than with SO intact (27.7%)+-8.2%), but the difference did not reach significance (p = 0.08). Neither GB emptying (9.8”/, t- 2.9(% vs. 9.4”/0 +5.1%) nor the maximal rate of duodenal delivery of “C micromoles (1.8 i 0.4 vs. 2.1 ir 0.6 times the steady-state rate of hepatic secretion) was significantly different with SO cannulated compared with SO intact. There is a contrast between the pattern of postprandial duodenal delivery of “C micromoles with SO intact compared with SO cannulated. With SO intact the rate of delivery of “C micromoles was greatest in the first 10 min after feeding. With SO function excluded by cannulation the rate of deliv-

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AND DIAMANT

GASTKOENTEROLOGY

Vol. 95, No. 4

GB

CD

o

jP(t)dt

3800

p E

0

80 D,

% 0 10 minutes

Figure

3. Expanded tracing of duodenal (D,, DZ, DJ, SO, common duct (CD), and GB pressure from 1 dog during phase III of an MMC. Channel 1 is the integrated area under the GB pressure waveform and tracing 5 is the integrated area under the SO pressure waveform. Note the rhythmic decrease of phase III contractions in the proximal duodenal and SO tracing, The phasic fluctuation in GB pressure is respiratory variation occurring at 9-12 cycle/min. The phasic variations in SO and duodenal contractile activity are occurring at 16 cycleimin.

ery of 14C micromoles was least in the first 10 min after feeding and gradually increased to a maximum 20-30 min after feeding. A greater proportion of 14C micromoles was delivered into the duodenum in the first 40 min after feeding with SO cannulated (42.5% * 9.2%) than with SO function intact (29.9% L 6.3%), but the difference did not reach significance (p = 0.1). In the lo-min interval from 20 to 30 min postprandially, when duodenal delivery with SO function excluded was maximal, the GB emptied 15.4% k 8.8% of the stored 14C micromoles, and the rate of duodenal bile acid delivery was equivalent to 2.2 k 0.6 times the steady-state rate of hepatic secretion. These values were not significantly different from those obtained with SO intact. Protocol Tree

2: Pressure

Dynamics

of the Biliary

A typical condensed record of duodenal, SO, common duct, and GB motility obtained in 1 dog is shown in Figure 1. Duodenal and biliary manometry

tracings are shown for one complete cycle of the MMC on the left, and for 20 min before and 60 min after feeding on the right. The duodenal traces show typical irregular contractile activity during late phase II, continuous contractile activity at 16 cycle/min during phase III, and quiescence during the succeeding phase I of the MMC. Feeding initiated continuous irregular contractile activity. Sphincter of Oddi motor activity was characterized by a basal pressure upon which were superimposed phasic contractions that were irregular during phases I and II, occurred with a maximum frequency of 16imin during phase III, and were absent briefly after feeding. Common duct pressures showed little variation beyond that induced by respiration. Baseline GB pressure increased before and remained elevated during phase III of the MMC, and was increased after feeding. Superimposed upon basal GB pressure was a 9-12 cycleimin respiratory variation of higher amplitude, particularly obvious during phase III. The net effect of variation in baseline and phasic GB and SO pressures can be seen in the

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HILIAKY IvlOTILITY 1075

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k’igurv

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4. Expanded tracing of duodenal (D,,D,. D.,), SO, common duct (CD). and GB pressure after feeding. Tracings I and 5 represent the integrated area under the GB and SO pressure waveform. respectively Note the immediate inhibition of SO phasic: c.ontrx:tile ac:ti\,ity, fall in baseline SO pressure, and rise in (;Bpressure in response to feeding.

slope of the lines in the second and fifth tracings, which represent the integrated average of GB and SO pressures. respectively. Figure 3 is a more detailed tracing of duodenal and biliary motility during phase III of this MMC. In the most proximal duodenal lead there is a cyclic inhibition of duodenal phase III contractile activity. This inhibition occurs during bursts of gastric contractions and has been shown to be vagally mediated (21). In 13 of 14 experiments in 3 dogs the phasic contractile activity of the SO during phase III showed a pattern of cyclic decrease similar to the lragally mediated inhibition of duodenal phase III contractions. Cyclic. apparently reciprocal, elevations of GB pressure concurrent with inhibition of phase III phasic contractile activity of the SO were observed in four experiments in 1 of 3 dogs. In these four experiments common duct pressure increased briefly with each contraction of the GB. A detailed tracing of the postprandial period is shown in Figure 4. It shows the typical inhibition of baseline pressure and phasic SO contractile activity, and a rise in GB pressure that occurred immediately after feeding that lasted for 2.5 2 1.4 min. Over the

next 35 min animals showed a slight increase in basal SO pressure, return of irregular phasic contractile activity in the SO, and a decrease in GB pressure to a more modest level. The GB again began to show irregular contractile activity and a slow increase in baseline pressure 40-60 min after feeding. In Figure 5 the mean of the average values for each of 3 dogs for common duct, SO, and GB pressures during the interdigestive period are shown. During the MMC, common duct pressure fluctuated between an end-expiratory basal level of 2-3 mmHg and an inspiratory peak of 8-9 mmHg. Although the magnitude of the difference was small, basal SO pressure was significantly greater in the first compared with the second half of the duodenal cycle period, as shown by the following two parameters. First, basal SO pressure exhibited a low-amplitude fluctuation that reached a single peak (4.6 * 0.3 mmHg) at 15%,, and then decreased to a significantly different (p < 0.05) trough value (2.2 + 0.2 mmHg) at 85% of the MMC cycle period. Second, the sum of basal SO pressure obtained at 5% intervals from 5% to 500/o compared with from 55%, to lOfl%, of the MMC cycle period was significantly different (47.8 t 3.5 vs. 27.6

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GASTROENTEROLOGY

AND DIAMANT

A. Common Bile Duct

!

cycle period (90.2 ? 11.5 vs. 135.3 2 The frequency of phasic SO contractile ure 6, upper panel) was -8 cycle/min half of the MMC cycle period, decreased 6.3 t 1.8 cycleimin at 65% of the cycle increased significantly (p < 0.01) to a 11.1 + 2.4 cycleimin at 95% of the period.

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5. (A] Basal (end-expiratory] and peak (inspiratory) common bile duct pressure: (B] minimum basal, integrated average, and maximum phasic SO pressure; and (C) integrated average GB pressure in the interdigestive period.

2 1.8; p < 0.05). Basal SO and end-expiratory common duct pressures were virtually identical, never being >2 mmHg apart. Integrated average SO pressure was about 10 mmHg for the first half of the MMC cycle period, decreased to a low of 8.8 * 1.9 mmHg at 65% of the MMC cycle period, and increased to a maximum of 14.5 + 3.7 mmHg at 95% of the MMC cycle period. Maximum phasic SO pressure averaged 25 mmHg, but increased to -35 mmHg during phase III. Gallbladder pressure was greater in the second compared with the first half of the duodenal cycle period. It was least at 20% (6.8 * 0.9 mmHg), and then increased to a significantly different (p < 0.05) peak value (15.4 * 7.2 mmHg) at 95% of the MMC cycle period. The sum of GB pressure obtained at 5% intervals from 5% to 50% was less than that from 55% to 100% of the MMC

p = 0.1). activity (Figfor the first to a low of period, and maximum of MMC cycle

55;

The mean of the average values for each of 3 dogs for common duct, SO, and GB pressures during the postprandial period is graphed in Figure 7. Feeding caused a slight increase, but no significant change in end-expiratory (basal) or inspiratory (peak) common duct pressure. Basal SO and end-expiratory common duct pressures were always within 1 mmHg of each other, except for a brief fall in basal SO pressure immediately after feeding. There was a significant (p < 0.05) decrease in both basal SO pressure (4.1 2 1.2 to 1.9 ? 0.8 mmHg) and frequency of SO contrac6, lower panel; 7 + 3.7 to 1.2 -+ tions (Figure 9.9/min), and a significant (p < 0.05) increase in integrated average GB pressure (7.2 t 0.4 to 27.2 +- 9 mmHg) in the 2 min after, compared with the 2 min before, feeding. Both integrated average and peak phasic SO pressure reflected this immediate postprandial response. Between 10 and 50 min after feeding GB pressure maintained more modest levels in the range of 10 mmHg. After this there was again a tendency to increasing GB pressure. In a single sham-feeding experiment performed in each of 3 dogs the offering of food was associated with an immediate inhibition of SO phasic contractile activity, but no change in baseline SO pressure and no elevation of GB pressure.

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Figure

6. The frequency gestive (upper periods.

of phasic

SO contractions

panel) and postprandial

in the interdi(lower paneI)

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and duodenal bile acid delivery increases to a maximum concurrent with partial emptying of the GB before phase III of the MMC. The net function of the GB during fasting is one of storage. The diversion of hepatic biliary output away from the GB and into the duodenum. and the partial emptying of the GB before phase III of the MMC, are associated with a small decrease in basal SO pressure, a reduction in frequency of phasic SO contractile activity, and an increase in average GB pressure. Reversal of this trend occurs with initiation of the next MMC and is associated with GB filling. The pattern of bile flow and biliary tree pressure dynamics in the first hour after feeding is separable into ~M’Operiods. Immediately after feeding, from 0 to 10 min, there is a decrease in basal SO pressure and SO contractile activity and an increase in average GB pressure. The GB to basal SO pressure gradient is maximal and peak rates of duodenal bile acid delivery and GB emptying occur. Over the next 40 min, the GB to basal SO pressure gradient decreases to more modest levels and net GB emptying is sustained.

C. Gallbladder Bile Flow

ii

o-

-20

0

20

40

60

TIME (mid Figuw

7. (A] Basal (end-expiratory) and peak (inspiratory) conman bilr: duct pressure; (B] minimum basal, integrated a~wage. and maximum phasic SO pressure: and (C) integrated a\~:rage GH pressure in the postprandial Iwriod.

Discussion These experiments delineate the biliary prcssure dynamics responsible for the partition of hepatic biliary output between the GB and duodenum during fasting and after feeding. There is a direct relationship between the magnitude of the GB to basal SO pressure gradient and the proportion of hepatic output directed away from GB storage and delivered into the duodenum (Figure 8). In the interdigestive period rhythmic partial GB emptying and refilling arc coordinated with cyclic activity of the MMC in the duodenum. Hepatic biliary output is directed into the GB, and duodenal bile acid delivery is minimal for the first half of the MMC cycle period. In the second half of the MMC cycle period the proportion of hepatic bile stored in the GB decreases

Our results confirm previous work demonstrating a cyclical increase in the rate of delivery of bile acids into the duodenum during phase II of the duodenal MMC (13,15,22-25). They show that the rhythmic fluctuation in duodenal bile acid delivery, which occurs in association with the MMC is a function of coordinated GB and SO motor activity. Our data. showing an immediate peak followed by a lower sustained rate of duodenal bile acid delivery after feeding, support the results of early investigators (26,27). and differ slightly from a more recently (26) republished study (7). Elman and McMaster ported that at the perception and taking of food there was a sudden, pronounced increase in the flow of bile into the intestine that lasted several minutes. Then. after a brief cessation of flow. a second period of flow commenced. Gilsdorf (27) reported a similar biphasic response of the canine biliary tree to feeding. Traynor et al. (7) recently reported a linear increase in cumulative duodenal bile acid output commencing 15 min after feeding. They did not see an immediate postprandial increase of duodenal bile acid delivery even though a sharp rise in GB pressure \\Tas noted within 4 min of eating. A methodologic problem explains the discrepancy. Duodenal bile acid delivery in Traynor’s experiments was measured using duodenal markr>r perfusion with the duodenal aspiration site at the ligament of Treitz, whereas in our study the aspiration site was 5 cm distal to the SO. We believe that their longer mixing segment introduced an artifactual clelay (a greater

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lnterdiiestive 100 w-

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Postprandial

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Vol. 95, No. 4

Period

lOOr

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.E EPATIC OUTPUT ---__--------_

2 E

30

l

Mean Gallbladder

0

Basal Sphincter

Pressure of ODDI Pressure

20

8! 2

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z !z 0

20

ELAPSED

40

PERCENT CYCLE

Figure

60

00

100

OF DUODENAL

TIME (min)

PERIOD

8. Composite of duodenal delivery of 14C micromoles in the upper panel and basal SO and GB pressure in the lower panel during the interdigestive and postprandial periods. Note that duodenal delivery and GB emptying in both the interdigestive and postprandial periods are proportionate to the magnitude of the GB to basal SO pressure gradient. Note also that in the postprandial period there is an immediate release of bile into the duodenum coincident with an immediate decrease in basal SO and increase in integrated average GB pressure

transit time) in the measurement duodenal bile acid delivery. Sphincter

of the onset

of

of Oddi

Sphincter of Oddi function remains controversial (3,5), due in part to marked interspecies differences. In the opossum, (a) the SO is about 3 cm in length and extraduodenal (2) and exhibits peristaltic contractions that empty SO contents into the duodenum (28) and (b) i.v. cholecystokinin-octapeptide in vivo has an excitatory effect on SO motor activity (29,30). In the dog, (a) the SO is -1 cm in length, intramural where it may be affected by the contractions of scattered bundles of encircling duodenal muscle (2), and exhibits peristaltic activity, which contributes to output resistance (3~3) and (b) i.v. cholecystokinin-octapeptide in vivo has an inhibitory effect on SO motility (31-33). In our experiments, there was an association between decreased basal SO pressure and frequency of phasic SO contractions and increased duodenal bile acid delivery in both the interdigestive and immediate postprandial periods. The magnitude of the decrease in basal SO pressure is small and it is likely that its physiologic contribution to the increase in duodenal bile acid delivery in the latter half of the MMC is also small. The GB makes a proportionally much larger

contribution to the increase in the GB to basal SO pressure gradient during the latter half of the MMC. This conclusion is consistent with the fact that when the SO was excluded by cannulation in these and previous experiments (13) there was persistence of the cyclical rise in duodenal bile acid delivery in the latter half of the MMC. Although phasic SO contractile activity is peristaltic in the dog (3) and may assist in clearing the SO segment, our results are consistent with previous work in this species showing that the net effect of canine SO motor activity is that of an output resistance favoring the partition of hepatic biliary secretion into the GB and away from the duodenum (13). Basal SO pressure does not exceed endexpiratory common duct pressure, and bile flows into the duodenum during intervals of decreased phasic SO contractile activity. Additional support for such a role is provided by our observation that total duodenal bile acid delivery in both the interdigestive and postprandial periods tended to be greater with SO excluded by cannulation (output resistance set at 0) than with SO function intact. Further, the immediate decrease in basal SO pressure and phasic activity that occurs after feeding is a factor mediating the immediate postprandial peak in duodenal bile acid delivery-if it is abolished by cannulation of the SO, there is no early peak in delivery.

HILIAKY Fv\/ZOTILITY

October 1988

Gallbladder Gallbladder function has been assessed using a variety of techniques, each of which have their disadvantages. Changes in intraluminal GB pressure may not be equivalent to alterations in the state of GB smooth muscle tension when the cystic duct is patent and allows bile outflow. External force displacement transducers are unable to differentiate between components of emptying caused by active GB contraction and passive emptying that might result from a decrease in outflow resistance. Changes in GB volume determined through the use of cholecystography, ultrasound, radioisotope scintigraphy, or the calculated difference between measured hepatic secretion and duodenal bile acid delivery indicate the presence of a pressure gradient sufficient to cause filling or emptying, but not the mechanism of its development. In our experiments we sought to obtain a clear understanding of biliary physiology through a knowledge of both bile flow and biliary pressure dynamics. We have shown a pattern of GB filling in the first half of the MMC cycle period, followed by an increase in GB pressure and net partial GB emptying in phase II. Our results are consistent with previous reports in the opossum (341,dog (7,13,35,36), and human (8,9,10). Gallbladder emptying was not just the passive result of a decrease in basal SO pressure between 60% and 90% of the MMC cycle period. It occurred because of an increase in GB pressure, which must have resulted from active GB contraction. During the first postprandial hour an immediate (within 1 min) increase in GB pressure occurred in association with peak GB emptying and duodenal bile acid delivery (from 0 to 10 min). This was followed by an isotonic phase (from 10 to 50 min) of lower pressure and sustained GB emptying. This finding is consistent with earlier descriptions of postprandial changes in (;B pressure and duodenal bile delivery in the dog (27,37) and also with the more common type 1 postprandial contractile response of the canine GB reported by Takahashi et al. (38). Traynor et al. (7) also described an immediate transient increase in GB pressure followed by an isotonic phase. Neural

Coordination

The pattern of rhythmic decrease in the intense phasic contractile activity of the SO during interdigestive phase III of the MMC matches the vagally dependent inhibition of duodenal phase III contractions seen during bursts of gastric activity (21).This, and the almost instantaneous postprandial decrease in SO pressure, increase in GB pressure, and initiation of GB emptying in our animals

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also suggest a cephalic neural (perhaps vagal) control mechanism, rather than one mediated through the release of cholecystokinin (39). Elman and McMaster (26) came to similar conclusions in 1926-the mere perception of food, before any had been given to the animals [dogs), initiated a fall in biliary outflow resistance and a flow through the ampulla, and was due, most obviously, to a psychic reflex. In humans, sham feeding results in GB emptying and appears to be mediated via a vagal cholinergic pathway (9). Sham feeding of our animals produced only the immediate decrease in frequency of SO contractions, without the decrease in basal SO pressure, or elevation of GB pressure. Initiation of the complete response may require more than just the presentation of a meal. (40) has shown reflex inhibition of the Wyatt canine SO mediated through the celiac ganglion after electrical or mechanical stimulation of the GB. The existence of such a pathway might explain the reciprocal inhibition of phase III SO contractile activity and elevation of CB pressure, which we observed in four experiments. Recent in vitro work showing that cholecystokinin-octapeptide has no direct influence on canine SO muscle (4) provides additional support for an extramural neural mechanism controlling SO motility. In conclusion, coordinated SO relaxation and GB contraction regulates both cyclic interdigestive and immediate postprandial duodenal bile acid delivery in the dog. Our data suggest neural modulation of biliary motility, and a cephalic phase of immediate postprandial GB emptying.

Keferences 1. Hofmann

AY. The enterohepatic circulation of bile acids in man. Clin Gastroenterol 1977;6:3&24. 2. Boyden EA. The sphincter of Oddi io man and certain representative mammals. Surgery 1937;1:25--37. 3 Scott RB. Strasberg SM, El-Sharkawy TY. IIiamant NE. Fasting canine biliarg secretion and the sphincter of Oddi. Gastroenterology 1984;87:793-804. 4. Bauer AJ. Schmalz PF. Szurszewski JH. Effect of CCK-OP on mechanical and intracellular activities of the choledochoduodenal junction of various mammals (abstr). Gastroenterology 1986:90:1340. 5 Sarles JC. Hormonal control of sphinc.ter of Oddi. Dig Dis Sci 1986:31:208-12. 6. Geenen JE. Hogan WJ, Dodds WJ. Stewart ET. Arndorfer RC. lntraluminal pressure recording from the human sphincter of Oddi. Gastroenterology 1980;78:317-24. 7. Traynor 01. Dozois RR, DiMagno EP. Canine interdigestive and postprandial gallbladder motility and emptying. Am J Physiol 1984;246:C426-32, 8. Svenberg T, Christofides ND, l:itzpatrick hlL. Areola-Oritz P, Bloom SK. Welbourn RB. Interdigestive biliary output in man: relationships to fluctuations in plasma motiiin and effect of atropine. Gut 1982;23:1024-8. 9. Fisher RS. Kock E. Malmud LS. (&llbladder emptying re-

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20. 21.

22.

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24.

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sponse to sham feeding in humans. Gastroenterology 1986:90: 1854-7. Toouli J, Dent J, Bushel1 M, Wycherley A, Stevenson G. Gallbladder emptying in relation to duodenal interdigestive migrating motor contractions (abstr). Gastroenterology 1985; 88:1616. Szurszewski JH. A migrating electric complex of the canine small intestine. Am J Physiol 1969;217:1757-63. Vantrappen G, Janssens J, Hellemans J, Ghoos Y. The interdigestive motor complex of normal subjects and patients with bacterial overgrowth. J Clin Invest 1977;59:1158-66 Scott RB, Eidt PB, Shaffer EA. Regulation of fasting canine duodenal bile acid delivery by sphincter of Oddi and gallbladder. Am J Physiol 1985;249:G622-33. Malagelada JR, Go LW, Summeroskill WHJ. Different pancreatic, and biliary responses to solid, liquid or homogenized meals. Dig Dis 1979;24:101-10. Peeters TL, Vantrappen G, Janssens J. Bile acid output and the interdigestive motor complex in normal and in cholecystectomy patients. Gastroenterology 1980;79:678-81. Fordtran JS. Marker perfusion techniques for measuring intestinal absorption in man. Gastroenterology 1966;51: 1089-93. O’Maille ERL, Richards TG. Short AH. The influence of conjugation of cholic acid on its uptake and secretion: hepatic extraction of taurocholate and cholate in the dog. J Physiol (London] 1967;189:337-50. Cowen AE, Korman MG, Hofmann AF, Thomas PJ. Plasma disappearance of radioactivity after intravenous injection of 1975;68: labelled bile acids in man. Gastroenterology 1567-73. O’Maille ERL, Richards TG, Short AH. Observations on the elimination rates of single injections of taurocholate and cholate in the dog. Q J Exp Physiol 1969;54:296-310. Snedecor GW, Cochran WG. Statistical methods. 6th ed. Ames, Iowa: Iowa State University Press, 1967. Hall KE, El-Sharkawy, Diamant NE. Vagal control of migrating motor complex in the dog. Am J Physiol 1982;243: G276-84. DiMagno EP, Hendricks JC, Go VLW, Dozois RR. Relationship among canine fasting pancreatic and biliary secretion, pancreatic duct pressure and duodenal type III motor activityBoldyreff revisited. Dig Dis Sci 1979;24:689-95. Keane FB, DiMagno EP, Dozois RR, Go VLW. Relationships among canine interdigestive exocrine pancreatic and biliary flow, duodenal motor activity, plasma pancreatic polypeptide, and motilin. Gastroenterology 1980;78:310-6. Vantrappen GR, Peeters TL, Janssens J. The secretory component of the interdigestive migrating motor complex in man. Stand J Gastroenterol 1979;14:663-7. Scott RB, Strasberg SM, El-Sharkawy TY, Diamant NE. Regulation of the fasting enterohepatic circulation of bile acids by the migrating myoelectric 1983;71:644-54.

complex

in dogs.

I Clin Invest

26. Elman R, McMaster P. The physiological variations in resistance to bile flow to the intestine. J Exp Med 1926;44:151-71.

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27. Gilsdorf RB. The effect of simulated gallstones on gallbladder pressures and bile tlow response to eating. Surg Gynecol Obstet 1974;138:161-8. 28. Toouli J, Dodds WJ, Honda R, et al. Motor function of the opossum sphincter of Oddi. J Clin Invest 1983;71:208-20. 29. Becker JM, Moody FG, Zinsmeister AR. Effect of gastrointestinal hormones on the biliary sphincter of the opossum. Gastroenterology 1982;82:1300-7. 30. Honda R, Toouli J, Dodds W, Ceenen JE, Hogan WJ, Hoh Z. Effect of enteric hormones on sphincter of Oddi and gastrointestinal myoelectric activity in fasted conscious opossums. Gastroenterology 1983:84:1-g. 31. Raih JJ. Ashmore CS, LVilson FD, et al. Effect of enteric hormones on the canine choledochal sphincter. Gastroenterology 1973;64:A-1041787. 32. Lin TM. Action of gastrointestinal hormones and related peptides on the motor function of the biliary tract. Gastroenterology 1975:69:1006-22. 33. Sarles JC. Rabaud B, Devaux MA. Action de la cholecystokine sur la motricite des voies biliares et l’evacuation de la bile chez le lapin in viva. Gastroenterol Clin Biol 1981;5:577-82. 34. Takahashi I. Kern MK, Dodds WJ, et al. Contraction pattern of opossum gallbladder during fasting and after feeding. Am J Physiol 1986;25O:G227-35. 35. ltoh Z. Takahashi I. Periodic contractions of canine gallblad1981;240: der during the interdigestive state. Am J Physiol G183-9. 36. Itoh Z, Takahashi I, Nakaga M, Suzuki T, Arai H, Wakabayoshi K. Interdigestive gallbladder bile concentrations in relation to periodic contractions of gallbladder in the dog. Gas1982;83:645-51. troenterology PD. Elman R. On the expulsion of bile by the 37. McMaster gallbladder and a reciprocal relationship with sphincter activity. J Exp Med 1926;44:173-98. I, Nakaya M, Suzuki T, Itoh Z. Postprandial 38. Takahashi changes in contractile activity and bile concentrations in gallbladder of the dog. Am J Physiol 1982;243:G365-71. of the gallbladder. Gastroenterology 39. Banfield WJ. Physiology 1975;69:770-7. of the sphincter of Oddi to the 40. Wyatt AP. The relationship stomach, duodenum and gallbladder. J Physiol (London] 1967;193:225-43. 41. Scott RB. Factors controlling fasting and postprandial duodenal bile acid delivery. Clin Invest Med 1986;9:A49.

Received March 31. 1987. Accepted March 23, 1988. Address requests for reprints to: Brent Scott, M.D., University of Calgary, Faculty of Medicine, Department of Pediatrics, Health Sciences Centre, 3330 Hospital Drive N.W., Calgary. Alberta T2N 4N1, Canada. This work was supported through the funding of the Intestinal Disease Research Group, University of Calgary. The authors thank Il. Kirk for technical assistance and Mrs. L. Tokarek for typing the manuscript. Portions of this work have been published in abstract form (41).