Effect of Pancreatic Juice and Trypsin on Oleic Acid-Stimulated Pancreatic Secretion and Plasma Secretin in Dogs

Transcription

1 GASTROENTEROLOGY 1989;96: Effect f Pancreatic Juice and Trypsin n Oleic Acid-Stimulated Pancreatic Secretin and Plasma Secretin in Dgs K. SHIRATORI, Y. H. JO, K. Y. LEE, T. M. CHANG, and W. Y. CHEY The Isaac Grdn Center fr Digestive Diseases and Nutritin, The Genesee Hspital; and University f Rchester Schl f Medicine and Dentistry, Rchester, New Yrk We have investigated a negative feedback mechanism in the intestinal phase f pancreatic excrine secretin in dgs with gastric cannulas and Thmas dudenal cannulas in whm pancreatic juice was cllected by cannulatin f the main pancreatic duct. Intradudenal infusin f leic acid emulsin in a dse f 18 mmllh resulted in a significant increase in pancreatic secretin f water, bicarbnate, and prtein, which was accmpanied by increased plasma cncentratins f bth secretin and chlecystkinin. Infusin f pancreatic juice r bvine trypsin int the dudenum significantly inhibited the leic acid-stimulated pancreatic secretin. This inhibitin cincided with a significant decrease in plasma secretin level, whereas plasma chlecystkinin cncentratin was nt affected by either pancreatic juice r trypsin. Neither pancreatic secretin nr plasma secretin cncentratin was affected by intradudenal administratin f NaHCO a slutin. The trypsin-induced suppressin f pancreatic secretin was prevented by intravenus administratin f secretin in a dse that achieved a plasma secretin level cmparable t that during the leic acid administratin. This study indicates that a negative feedback mechanism is perative in the intestinal phase f pancreatic excrine secretin in dgs, and endgenus secretin plays a significant rle in the mechanism. Afeedback regulatry mechanism f pancreatic excrine secretin by trypsin r pancreatic juice has been recgnized in several animal species including rats (1-8), pigs (9), and chickens (10) and in humans (11-15). Recently, it has been shwn that this feedback regulatin f pancreatic excrine secretin is mediated by a suppressive effect f pancreatic juice r trypsin n release f chlecystkinin (CCK) in bth rats (6-8) and humans (14,15). Mrever, it has been suggested that secretin may playa significant rle in the negative feedback mechanism in humans (12,16) and rats (17,18). Hwever, this phenmenn was nt fund in dgs in either the pstprandial state r the interdigestive state (19). The purpse f the present study was t investigate a negative feedback mechanism in the intestinal phase f pancreatic excrine secretin in dgs. Specifically, we investigated the rle f circulating gut hrmnes, including secretin and CCK, in the mechanism. Materials and Methds Six healthy mngrel dgs f bth sexes, weighing between 18 and 20 kg, were prepared with bth gastric and Thmas dudenal cannulas as described previusly (20). A Thmas cannula was placed in the dudenum, ppsite t the main pancreatic duct pening while the accessry pancreatic duct was ligated. Experiments were carried ut at least 3 wk after the surgical prcedure. After an 18-h fast during which dgs were allwed free access t drinking water, the animals were placed n a Pavlv stand. Bth gastric and Thmas dudenal cannulas were gently irrigated with warm tap water, and drained fr 1 h befre experiments were started. As gastric juice was drained by gravity via gastric cannula thrughut the experiment, the main pancreatic duct was cannulated with a glass tube and then the tube was immbilized within the Thmas cannula using a rubber crk t avid pullut. The tip f the glass tube (OD, 3 mm; ID, 1.5 mm) was cnstructed with a spherical-shaped bulb (OD, 4-5 mm; ID, 2.0 mm) and a sharp and blunt tip (OD, 1.2 mm; ID, 1.0 mm), s that it culd be inserted easily int the duct and be held tightly by the sphincter muscle. The entire length f the tube was abut 10 cm. The external tip f the glass tube was cnnected t a plastic tube t cllect pure pancreatic juice. Abbreviatin used in this paper: CCK, chlecystkinin by the American Gastrenterlgical Assciatin /89/$3.50

2 May 1989 ROLE OF TRYPSIN ON CANINE PANCREATIC SECRETION 1331 One plyethylene tube was placed in the dudenum thrugh a Thmas dudenal cannula t infuse either 0.15 M NaCI slutin r leic acid emulsin. T wash dwn pancreatic enzyme frm mucsal surface f the upper intestinal lumen, 0.15 M NaCI slutin was infused int the dudenum at a rate f 0.42 mllmin fr at least 2 h, starting immediately after cannulating the main pancreatic duct. Oleic acid emulsin in 75.6 ml was prepared by diluting with 0.15 M NaCI slutin and by emulsifying 54 mml f leic acid (labratry grade; Fisher Scientific, Pittsburgh, Pa.) with 3% (vl/vl) plysrbate fr each experiment. The ph f leic acid emulsin was adjusted t 5.0 by adding a small amunt f 0.1 N NaOH. Oleic acid emulsin was infused int the dudenum at a rate f 0.42 mil min fr 3 h. Thus, the dse f leic acid administered was 18 mmllh. Test substances t be infused int the dudenum were prepared as fllws. Pure canine pancreatic juice was cllected in advance by cannulating the main pancreatic duct under stimulatin with intradudenal infusin f leic acid emulsin in the same dse as described abve in each dg. Pancreatic juice btained frm each dg was pled and kept at -20 C until later use. Bvine trypsin (Cpper Bichemical, Malvern, Pa.) in a dse f either 600 r 1200 mg was disslved in 25.2 ml f 0.1 M NaHC0 3 slutin. The temperature f all test slutins was adjusted t 37 C immediately befre they were administered int the dudenum. Starting frm the secnd hur f the intradudenal infusin f leic acid emulsin (281 msml), ne f the fllwing test slutins (including 0.1 M NaHC0 3 slutin, pure canine pancreatic juice, and 600 r 1200 mg f bvine trypsin) was infused, at a rate f 0.42 mllmin fr 1 h, int the dudenum thrugh anther plyethylene tube placed in the dudenum via a Thmas dudenal cannula. The dudenal trypsin cntent during dudenal infusin f leic acid and 600 mg f bvine trypsin was cmparable t that in experiments in which leic acid was infused int the dudenum withut diversin f pancreatic juice. In anther grup f 4 dgs with Thmas dudenal cannulas and gastric cannulas, identical experiments were carried ut by intradudenal infusing f leic acid emulsin and 1200 mg f trypsin. In additin, prcine secretin (Pharmacia, Piscataway, N.J.) disslved in 0.2% dg albumin slutin was administered intravenusly at a dsage f 0.03 CUlkg. h. During the experiments, pancreatic juice was cllected cntinuusly in 15-min samples in ice-chilled tubes while gastric secretin was drained by gravity via gastric cannula and discarded. Pancreatic juice was analyzed fr cncentratins f bicarbnate and prtein. A plyethylene catheter fr bld sampling was placed in a peripheral vein and kept patent by a slw infusin f 0.15 M NaCI slutin. Bld samples were btained in heparinized tubes at -15,0,45,60,90,105,120,135,165, and 180 min fr determinatin f plasma secretin and CCK cncentratins. The tubes were placed immediately n ice, and at the end f each experiment plasma was btained by a refrigerated centrifugatin at 2600 rpm. Plasma samples were stred fr future radiimmunassay at a temperature belw -20 C in the presence f 1.5 JLg!ml f bvine pancreatic trypsin inhibitr (type 1-P; Sigma, St. Luis, M.), 100 JLg!ml f sybean trypsin inhibitr (type 1-S; Sigma), and 9.9 x 10-9 M D-phenylalanyl-L-phenylalanyl L-arginine chlrmethyl ketne (Calbichem, San Dieg, Calif.), a ptent specific, irreversible inhibitr f plasma kallikreins. Determinatins Bicarbnate cncentratin f pancreatic juice was determined using a Crning CO 2 analyzer (mdel 965; Crning Glass Wrks, Crning, N.Y.) and prtein cncentratin using the biuret methd (21). Plasma cncentratin f secretin was determined by the methds described previusly (22). The plasma cncentratin f CCK was determined by a radiimmunassay methd that has been reprted in detail elsewhere (23). Briefly, a 2-ml sample f plasma was extracted n a XAD-2 resin clumn t remve nn-specifically interfering substances and assayed with anti-cck serum R-6-6. Althugh the antiserum cntains nly 40% f its binding sites recgnizing CCK-8, it was capable f measuring increments f CCK-8 up t 40 pm added t plasma as well as fllwing intravenus infusin f CCK-8 up t 0.24 JLg! kg. h. Recveries f bth CCK-33 and CCK-8 frm the XAD-2 clumn were cnsistent within the same assay but varied amng assays, ranging frm 50% t 85% fr CCK-33 and frm 60% t 90% fr CCK-8. T insure an insignificant cntributin f gastrin t plasma CCK data, plasma gastrin and recvery f gastrin expressed in CCK equivalents in the CCK assay were always determined. Analysis f Data All values were expressed graphically as mean ± 1 SE. The pancreatic secretry values in terms f vlume and utputs f bicarbnate and prtein btained frm the last 15-min samples f the first infusin hur with leic acid emulsin alne were cmpared with the basal values frm the 15-min samples befre starting the infusin f leic acid. Plasma secretin and CCK cncentratins 1 h after starting infusin f leic acid were cmpared with thse at 0 min. Statistical analysis fr these values was assessed by Student's t-test fr paired values. T determine the statistical significance f the suppressive effect f pancreatic juice r trypsin n leic acidstimulated pancreatic secretin cmpared with that f NaHC0 3 infusin, changes in vlume f pancreatic flw and bicarbnate and prtein utputs were btained by subtracting values fr the last 15-min samples during the 1-h infusin perid with each test slutin (including 0.1 M NaHC0 3, pancreatic juice, and trypsin) frm values btained frm the last 15-min samples f the first infusin hur with leic acid emulsin alne. The values f plasma secretin and CCK cncentratins were als btained by subtracting values at 60 min f each experiment frm values at 0 min immediately befre starting the infusin f each test slutin. The significance f changes in these variables in respnse t three different test substances was

3 1332 SHIRATORI ET AL. GASTROENTEROLOGY Vl. 96, N.5, Part 1 10, PANCREATIC JUICE + t " + TRYPSIN 600 mg/h + + TRYPSIN 1200 mg/h + " " ~ 6 E UJ ~ 4 ~...J > Figure 1. Effect f intradudenal infusin f NaHC0 3, pancreatic juice, r trypsin n vlume f leic acid-stimulated pancreatic secretin. In this and the fllwing figures the amunt f leic acid used was 18 mmllh. The vlume had significantly decreased when pancreatic juice r trypsin was administered simultaneusly. Each pint represents the mean ± SE f 12 experiments in 6 dgs in this and the fllwing figures. determined by analysis f variance. Fr thse respnse variables fr which statistically significant effects were fund, Newman-Keuls analyses were cnducted t determine which f the independent variables were respnsible fr the bserved differences. Test statistics f p < 0.05 were regarded as significant. Results Intradudenal infusin f leic acid emulsin at a rate f 18 mmllh resulted in a significant increase in pancreatic excrine secretin, including vlume and utputs f bth bicarbnate and prtein (Figures 1-3). This increase in pancreatic secretin paralleled significant increases (p < 0.01) in plasma cncentratins f bth secretin and CCK (Figures 4 and 5) (p < 0.01). Althugh the increase in bicarbnate utput paralleled the increase in its cncentratin, the prtein cncentratin decreased significantly in spite f increase in the prtein utput (Figures 2 and 3). When either pancreatic juice r trypsin in tw different dses was infused int the dudenum, there were significant decreases (p < 0.01) in pancreatic secretin f water (vlume), bicarbnate, and 1 c 1.2 'E ~ 1.0 w e j:' 0.8 i ~ 0.6 w ~ 0.4 z ~ 0.2 «~ 0 t PANCREATIC JUICE + rt , TRYPSIN 600 mglh + rt t TRYPSIN 1200 mglh t " Figure 2. Effect f intradudenal infusin f NaHC0 3, pancreatic juice, r trypsin n pancreatic bicarbnate secretin stimulated by leic acid.

4 May 1989 ROLE OF TRYPSIN ON CANINE PANCREATIC SECRETION 1333 NaHCO J.---. PANCREATIC JUICE TRYPSIN 600 mglh TRYPSIN 1200 mglh 160 E e;, r-l r-l 'i' C.s 0 'E z It) Q l- -e;, «. 6.~ l- I- Z ::> 80 ~ 30 w Q.. () I- z ::>, 0 + t, t, e.. (), 40 \ (t \,lilt Z 20? t (ryiil~ i Z W?"?"~??~~?'? tr~(( 9-'Y-r~ rrf h w l- I- e e Q g: Figure 3. Effect f intradudenal infusin f NaHC0 3, pancreatic juice, r trypsin n pancreatic prtein secretin stimulated by leic acid. prtein (Figures 1-3 and 6) as well as plasma cncentratin f secretin (Figures 4 and 7). The effects n bth pancreatic secretin and plasma secretin level were reversed within 15 min after dudenal infusin f pancreatic juice r trypsin was stpped. The plasma level f CCK, hwever, was nt affected by either pancreatic juice r trypsin (Figure 5). Neither pancreatic secretin nr plasma hrmne levels were influenced by intradudenal infusin f NaHC0 3 (Figures 1-7). As shwn in Figure 8, in 4 dgs with Thmas dudenal cannulas and gastric cannulas, intravenus administratin f prcine secretin in a dse f 0.03 Cu/kg. h prevented the trypsin-induced decrease in pancreatic secretin f bicarbnate and prtein. This dse f secretin achieved a plasma secretin cncentratin cmparable t that during the administratin f leic acid alne in these dgs. Discussin In the present study in dgs, we bserved that intradudenal administratin f pancreatic juice r trypsin suppressed the leic acid-induced increase in plasma secretin as well as pancreatic secretin (including vlume and utputs f bth bicarbnate and prtein). The decrease in pancreatic secretin cincided with a significant decrease in plasma secretin cncentratin, whereas plasma CCK level was nt influenced by trypsin r pancreatic juice. The suppressive effect f trypsin n pancreatic secretin was cmpletely blcked by i.v. administra- ~16 S z i= 12 w frl 8 (/) «~ 4 : NaHCO, + + PANCREATIC JUICE + ~ rl TRYPSIN 1200 mg/h + rl Figure 4. Effect f NaHC0 3, pancreatic juice, r trypsin n plasma secretin respnse t intra dudenal leic acid infusin. Plasma secretin cncentratin significantly decreased after infusin f trypsin r pancreatic juice.

5 1334 SHlRATORI ET AL. GASTROENTEROLOGY Vl. 96, N.5. Part 1 40 ~30 ~ 0 20 «2: 5 10 Q. + NaHCO. t + PANCREATIC JUICE t + TRYPSIN 600 mg/h t + TRYPSIN 1200 mg/h t " " " " 0 I I Figure 5. Plasma CCK respnse t intradudenal leic acid infusin. Effect f NaHC0 3, pancreatic juice, r trypsin n plasma CCK level is shwn. The CCK level was nt influenced by either ne f the three variables. tin f prcine secretin in a dse that mimicked plasma level f secretin achieved by leic acid emulsin. The latter bservatin indicates that the decreased endgenus secretin release was respnsible fr the trypsin-induced suppressin f pancreatic secretin stimulated by leic acid. It was shwn previusly in dgs that fllwing diversin f pancreatic juice frm the dudenum, return f pancreatic juice int the dudenum resulted in reductin f a meal-stimulated pancreatic secretin, including vlume and bicarbnate, but nt prtein (24,25). Hwever, this decrease by the infusin f pancreatic juice was ascribed t neutralizatin in the dudenum f gastric acid, as neutralizatin f acid in the dudenum was impaired when pancreatic secretin was diverted frm the dudenum. Sale et al. (26) reprted that intradudenal infusin f trypsin r pancreatic juice in dgs did nt affect pancreatic enzyme secretin stimulated by ingestin f a meal, nr was pancreatic enzyme secretin stimulated by intradudenal infusin f NaHC0 PANCREATIC TRYPSIN TRYPSIN 3 JUICE (600 mg) (1200 mg) NaHC0 PANCREATIC TRYPSIN 3 JUICE (600 mg) TRYPSIN (1200 mg) zit) ~i -4 Q. <l -80 p<o.ol vs. NaHC03 Figure 6. Changes in leic acid-stimulated pancreatic secretin in respnse t intradudenal administratin f NaHC0 3, pancreatic juice, r trypsin. Each value represents the mean ± SE f 12 experiments in 6 dgs. p<0.01 VS. NaHC0 3 Figure 7. Changes in plasma secretin levels during leic acid administratin in respnse t intradudenal infusin f NaHC0 3 pancreatic juice. r trypsin in 6 dgs.

6 May 1989 ROLE OF TRYPSIN ON CANINE PANCREATIC SECRETION 1335 BICARBONATE OUTPUT (meq/15 min) PROTEIN OUTPUT (mg/15 min) PLASMA SECRETIN (pm) 1.5 SECRETIN.,jTRYPSINL.,J; J SECRETIN ""TRYPSIN'",J;.. 16 SECRETIN '&TRYPSINj....& :;j O~~,----~----~--~ ~-~----~--~----~ ~~----~--~----~ Figure 8. Effect f intradudenal infusin f trypsin, 1200 mg/h, n leic acid-stimulated pancreatic secretin f bicarbnate and prtein. Simultaneus Lv. administratin f secretin, 0.03 CU/kg. h, ablished the inhibitry effect f trypsin n pancreatic bicarbnate and prtein secretin. This dse f secretin prduced a plasma level f secretin cmparable t that achieved by leic acid infusin (Figure 4). amin acids inhibited by the infusin f trypsin r pancreatic juice. The discrepancy between the present study and the previus studies cannt be readily explained at this time. On the ther hand, it was als shwn that pancreatic secretin increased in fasting dgs (19) when pancreatic juice was infused int the dudenum. Trypsin exhibited a similar stimulatry effect (19). The latter bservatin in dgs is in cntrast t the bservatins made in rats (1-8) r pigs (9). In a similar experiment with 3 dgs, we failed t bserve any significant change in pancreatic secretin in the inter digestive state (unpublished bservatin). The present study suggests strngly that, in dgs, a negative feedback cntrl mechanism n excrine pancreas functin is perative in the intestinal phase. The mechanism invlves release f secretin by leic acid, which cnfirms ur previus wrk (27). Our recent bservatin indicates that release f secretin is als invlved in a feedback mechanism in rats, as plasma secretin cncentratins increased significantly when pancreatic juice was diverted frm the dudenum (18). This increase was suppressed significantly by pancreatic juice. Furthermre, immunneutralizatin f circulating secretin with a high-titer rabbit-anti secretin serum blcked the increase in pancreatic secretin f water and bicarbnate during diversin f pancreatic juice frm the dudenum in these rats (18). The bservatins in dgs in the present study and in rats (18) crrbrates a study in humans (16) that indicated that a trypsin inhibitr given intradudenally increases the plasma secretin level significantly. Thus, a similar negative feedback cntrl mechanism may take place in humans als. In anther human study, Osnes and Hanssen (12) fund that when pancreatic juice was cllected by direct cannulatin, via an endscpe, f the main pancreatic duct in humans, the increases in bth pancreatic secretin and plasma secretin level due t intradudenal infusin f bile were suppressed by intradudenal infusin f pancreatic juice. Thus, it appears that secretin, as well as CCK, is invlved in a negative feedback regulatin f pancreatic excrine secretin. Intradudenal administratin f trypsin in humans was shwn t inhibit pancreatic excrine secretin stimulated by amin acids (13), phenylalanine, leic acid, r a meal (14,15). Owyang et al. (14) shwed clearly the inhibitry effect f intradudenal trypsin n phenylalanine-stimulated pancreatic secretin in a dse-dependent manner. The mechanism invlved in the inhibitry actin f pancreatic juice r trypsin n the release f secretin is nt well understd. Hwever, the present bservatin suggests that there may be a factr in the upper small intestinal mucsa that stimulates the release f secretin. As the release f secretin is suppressed by trypsin, the factr may well be a trypsin-sensitive peptide r prtein. Unlike in rats (7,8,28) and humans (14,15), the increase in the plasma level f CCK in respnse t intradudenal leic acid was nt blcked by trypsin. The reasn fr this discrepancy is nt apparent at the present time. In summary, we have shwn that in the intestinal

7 1336 SHIRA TORI ET AL. GASTROENTEROLOGY Vl. 96. N.5. Part 1 phase f pancreatic secretin in dgs stimulated by intradudenal infusin f leic acid emulsin, bvine trypsin in the dudenum significantly suppresses pancreatic secretin f water, bicarbnate, and prtein as well as the increase in plasma secretin cncentratin. Thus, it appears in dgs that a negative feedback inhibitry mechanism is perative in the intestinal phase f the pancreatic secretin f bicarbnate as well as prtein. Mrever, su ppressin f endgenus secretin release plays a significant rle in this mechanism. References 1. Green GM. Lyman RL. Feedback regulatin f pancreatic enzyme secretin as a mechanism fr trypsin inhibitr-induced hypersecretin in rats. Prc Sc Exp Bii Med 1972; 140: Green GM. Olds BA. Matthews G. Lyman RL. Prtein. as a regulatr f pancreatic enzyme secretin in the rat. Prc Sc Exp Bii Med 1973;142: Ihse I. Lilja p. Lundquist I. Trypsin as a regulatr f pancreatic secretin in the rat. Scand J GastrenterI1979;14: Nda A. Magee DF. Sarles H. The rle f gastric secretin in pstdiverted pancreatic hypersecretin in cnscius rats. J PhysiI1982;326: Miyasaka K. Green GM. Effect f partial exclusin f pancreatic juice n rat basal pancreatic secretin. Gastrenterlgy 1984;86: Luie DS. May D. Miller p. Owyang C. Chlecystkinin mediates feedback regulatin f pancreatic enzyme secretin in rats. Am J PhysiI1986;250:G Shiratri K. Chen YF. Chey WY. Lee KY. Chang TM. Mechanism f increased excrine pancreatic secretin in pancreatic juice-diverted rats. Gastrenterlgy 1986;91: Flsch UR. Canter p. Wilms HM. Schafmayer A. Becker HD. Creutzfeldt w. Rle f chlecystkinin in the negative feedback cntrl f pancreatic enzyme secretin in cnscius rats. Gastrenterlgy 1987;92: Ihse I. Lilja P. Effects f intestinal amylase and trypsin n pancreatic secretin in the pig. Scand J GastrenterI1970;14: Alumt E. Nitsan Z. The influence f sybean anti-trypsin n the intestinal prtelysis f the chick. J Nutr 1961;73: Ihse I. Lilja p. Lundquist I. Feedback regulatin f pancreatic enzyme secretin by intestinal trypsin in man. Digestin 1977;15: Osnes M. Hanssen LE. The influence f intra dudenal administratin f pancreatic juice n the bile-induced pancreatic secretin and immunreactive secretin release in man. Scand J GastrenterI1980;15: Slaff 1. Jacbsn D. Tillman CR. Curingtn C. Tskes P. Prtease-specific suppressin f pancreatic excrine secretin. Gastrenterlgy 1984;87: Owyang C. Luie DS. Tatum D. Feedback regulatin f pancreatic enzyme secretin-suppressin f chlecystkinin release f trypsin. J Clin Invest 1986;77: Owyang C. May D. Luie DS. Trypsin suppressin f pancreatic enzyme secretin-differential effect n chlecystkinin release and the enterpancreatic reflex. Gastrenterlgy 1986;91: Watanabe S. Shiratri K. Takeuchi T. Chey WY. Intrajejunal administratin f a synthetic trypsin inhibitr (camstate) stimulates the release f endgenus secretin. but nt chlecystkinin in humans (abstr). Gastrenterlgy 1986;90: Watanabe S. Chang JH. Shiratri K. Takeuchi T. Chey WY. Intradudenal administratin f a synthetic trypsin inhibitr (camstate) stimulates endgenus release f secretin in dgs and rats (abstr). Dig Dis Sci 1986;31: Sun G. Lee KY. Chang TM. Chey WY. Rle f endgenus secretin in negative feedback regulatin f excrine pancreas in rats (abstr). Dig Dis Sci 1986;31:A Magee DF. Naruse S. Effect f pancreatic juice n basal pancreatic and gastric secretin in dgs. J Physil 1982;330: Thmas JE. An imprved cannula fr gastric and intestinal fistulas. Prc Sc Exp Bii Med 1941;46: Grnall AG. Bardawill CF. David MM. Determinatin f serum prtein by means f biuret reactin. J Bii Chern 1949;177: Chang TM. Chey WY. Radiimmunassay f secretin: a critical review and current status. Dig Dis Sci 1980;25: Chang TM. Chey WY. Radiimmunassay f chlecystkinin. Dig Dis Sci 1983;28: Annis D. Hallenbeck GA. Effect f excluding pancreatic juice frm dudenum n secretry respnse f pancreas t a meal. Prc Sc Exp Bii Med 1951;77: Cke AR. Nahrwld DL. Grssman MI. Diversin f pancreatic juice n gastric and pancreatic respnse t a meal stimulus. Am J PhysiI1967;213: Sale JK. Gldberg DM. Fawcett AN. Wrms ley KG. Chrnic and acute studies indicating absence f excrine pancreatic feedback inhibitin in dgs. Digestin 1977;15: Watanabe S. Chey WY. Lee KY. Chang TM. Secretin is released by digestive prducts f fat in dg. Gastrenterlgy 1986;90: Liddle RA. Green GM. Cnrad CK. Williams JA. Prteins but nt amin acids. carbhydrates. r fats stimulate chlecystkinin secretin in the rat. Am J PhysiI1986;251:G Received Nvember Accepted December Address requests fr reprints t: William Chey. M.D. GI Unit. WW5. The Genesee Hspital. 224 Alexander Street. Rchester. New Yrk This study was supprted by the Natinal Institutes f Health (ADDK grant 25962)' and in part by The Genesee Hspital Gastrintestinal Research Fund. The authrs thank Barbara Wnneberg and Anne Brun fr preparatin f the manuscript.