Effects of somatostatin on the external secretion of the pancreas of the rat

0016~5085/78/7606-0832$02.00/O

GA~TROENTEROLOGY 75832-837,1978 Copyright0 1978by the AmericanGastroenterological Association

Vol. 75, No. 5 Printedilz USA.

EFFECTS OF SOMATOSTATIN ON THE EXTERNAL SECRETION OF THE PANCREAS OF THE RAT JACQUES CHARIOT, PH.D.,

CLAUDE ROZE, M.D.,

PH.D.,

CHARLES VAILLE, PH.D.,

AND CHARLES DEBRAY, M.D. Laboratoire de GastroentPrologieA, Hhpital Bichat, and Laboratoire de Physiologie Cellulaire, Uniuersitt! Pierre et Marie Curie, Paris, France

The effects of somatostatin on the secretions of the exocrine pancreas were studied in anesthetized and conscious fistula rats. Somatostatin resulted in a dose-dependent decrease of basal secretion (flow, bicarbonate, protein) in conscious rats. In anesthetized rats, basal secretion was initially augmented by bolus injections of 10 to 50 M per kg and was subsequently decreased by venous infusions of somatostatin at 1.5 to 100 pg. kg-l. hr-‘. This inhibition, which was poorly dose dependent, was greater for protein secretion than for that of water and electrolytes. Somatostatin inhibited caerulein-stimulated protein secretion by 40 to 50% but had no effect on secretion stimulated by exogenous and endogenous secretin. Somatostatin markedly inhibited secretion stimulated by 2-deoxyglucose and by electrical stimulation of the vagus nerves in a dose-dependent fashion (protein and bicarbonate exhibited a maximal inhibition of 85%). Acetylcholine-stimulated secretion was also inhibited by somatostatin, but the maximal inhibitions observed were only 50% for protein and 60% for bicarbonate. These findings agree with the hypothesis that somatostatin infusion leads to both a decrease of acetvlcholine release at nerve endings and to a direct inhibition at the level of pancreatic effector cells. The effects of somatostatin (somatotropin release-inhibiting factor, SRIF) on exocrine pancreas secretion apparently vary with the species and experimental conditions. Thus, inhibition of secretin-stimulated secretion has been described in dogs, l-3 cats,4 and humans,:+ but not in pigs,8 rats,*-‘Oand humans. l1 Cholecystokinin (CCK)-stimulated secretion is inhibited in humans,H and rats, lo but not in dogs2 or the guinea pig pancreas in vitro. l2 Stimulatory effects of SRIF have been described in cats, rats, and guinea pigs. lsi4 It has recently been suggested that SRIF decreases acetylcholine release from the nerve endings of the guinea pig ileum electrically stimulated in vitro. lj The purpose of the present experiments was to study in detail the effects of SRIF on pancreatic secretions in rats in the context of the hypothesis of a decreased acetylcholine release at the pre- and/or postganglionic level in the vagal pathway to the pancreas. Materials and Methods Male Wistar rats (R. Janvier, 53 Le Genest, France), weighing between 250 and 300 g were used. Subacute fist&a in conscious rats. Animals were anesthetired with 100 mg of ketamine, a short term anesthetic, per kg of body weight by intraperitoneal injection. The upper part of Received February 13, 1978. Accepted June 12, 1978. Address requests for reprints to: Claude Raze, Laboratoire de Gastroenterologie A, Hopital Bichat, 170, bd Ney, 75877 Paris, Ckdex 18, France. Dr. Chariot is Charge de Recherches a I’INSERM.

the common biliary-pancreatic duct was then cannulated with a polyethylene catheter (0.3 mm inner diameter, 0.7 mm outer diameter) connected to a Silastic tube (no. 602-131). This enabled bile to be reintroduced into the duodenum. The lower part of the common bile duct was cannulated with a 5-cm long polyethylene catheter, which drained pancreatic juice through the abdominal wall. After recovering from anesthesia, the conscious rats were maintained in restraint jackets for the remainder of the experiment. They were intravenously infused with Hartmann’s Ringer solution containing 10% (w/v) glucose at a flow rate of 1.6 ml per hr. Pancreatic juice was not recirculated. Infusions of SRIF were performed 2 to 5 days alter catheterization. Acute fist&a in anesthetized rats. After an 18-hr fasting period, rats were anesthetized with an intramuscular injection of 1.125 g of ethylurethane per kg. A catheter was then introduced into the upper part of the common bile duct in order to divert bile. A second catheter was introduced into the lower part of the common bile duct and connected to a Tshaped glass tube (Technicon, A 10, Technicon Instruments Corp., Tarrytown, N.Y.) whose other branches were connected to a stock bottle of diluent (KU, 30 mM) and a peristaltic pump (Gilson Minipuls Gilson Medical Electronics, Inc., Middleton, Wis., Technicon Instruments Corp, Carrytown, N.Y.) by Tygon tubes (0.51 mm inner diameter). The pump aspirated continuously the mixture of juice and diluent at the rate of 4 ml per 20 min, and 20-min fractions of diluted juice were recovered with a fraction collector. Hydrostatic pressure in the vicinity of the pancreatic ducts was maintained at -2 to -3 cm of water. Central temperature of the rats was maintained at 38 2 05°C with an automated device.16 Drugs and treatments. Pancreatic secretions were studied under basal conditions, i.e., subacute and acute fistulae, and

832

SOMATOSTATIN

November 1978

AND PANCREATIC

833

SECRETION

after the administrationof various stimulatory agents in rebound effect could be observed after the infusion acute fistula. These agents were chosen to mimic the major period; its maximal amplitude was +30% for flow and neural and hormonal physiological stimuli of the pancreas? + 70% for protein and bicarbonate outputs. cholinergic central stimulation with 2-deoxy-n-glucose (2DG), Anesthetized rats. These animals are a model with preganglionic stimulation with vagal electrical stimulation, low basal rates of pancreatic secretion. ly Single bolus peripheral stimulation with acetylcholine, and hormonal stimplus infusions of SRIF lead to a biphasic effect. All of ulation with secretin and caerulein, the latter a decapeptide the secretory parameters studied underwent an initial acting on CCK-pancreozymin (PZ) receptors. Caerulein was initially isolated from amphibian skin, but is presently a stimulation during the first minutes after the bolus and synthetic product, thus affording a more satisfactory degree of onset of SRIF infusion. This early stimulation is represented in the upper panel of figure 2 for protein, sodium, purity than extracted CCK-PZ. 2DG (Sigma Chemical Co., St. Louis, MO.) was intraveand bicarbonate outputs. The per cent increase of sonously introduced as a single bolus injection of 75 mg per kg, dium and bicarbonate outputs was greater than that of a dose assuring a half-maximal response. protein. An atropine dose of 1 mg per kg did not For electrical stimulation, the vagus nerves were first suppress the early stimulator-yeffect. severed in the neck, and their distal ends were then stimuAn inhibition of secretion subsequently occurred, lated with square pulses, 4 v, P-msec duration, 20 cycles per reaching a peak in the 40- to 60-min period and lasting set for a total of 20 min. A maximal response was obtained for the entire SRIF infusion period. The lower panel of under these conditions. Acetylcholine chloride was intravenously infused at 25 figure 2 represents the mean values of the per cent ~~g.kg-l min-’ for 20 min and was reinfused after an 80-min inhibition of protein, sodium, and bicarbonate outputs. delay at 100 pg. kg --I min-‘. These doses resulted in 20 and The 30 to 40% inhibition of protein output is apparently 90%, respectively, of the maximal response. poorly dose dependent. A significant inhibition of basal Three successive intravenous caerulein doses were succes- sodium and bicarbonate outputs could be observed only sively infused for 20 min each, separated by 40-min intervals: with the highest SRIF dose used, 100 pg. kg-’ hr-I. 5.5, 16.7, and 50 ng. kg-’ min’. These doses resulted in 10 to No rebound effect was observed at the end of SRIF 100% of the maximal response. infusion: secretion rates merely returned to base-line Secretin (GIH Research Laboratory, Karolinska Institutet, Stockholm, Sweden) was intravenously infused at 0.055,0.167, levels. Secretion variations during the entire period of SRIF and 0.50 clinical units. kg-’ min-’ for 20 min, each separated by 40-min intervals. These doses yielded 30 to 80% of the infusion are shown in figure 3 for a dose of 25 pg. kg-’ *hr-I. In this particular experiment, 5-min maximal response. Endogenous secretin release was provoked by duodenal fractions were collected during the -2O- to +40-min infusion with a solution of 75 mEq of HCl per liter at a rate of period in order to define more satisfactorily the biphasic

330 PEq. hr-I for 1 hr. The bicarbonate response obtained was about half-maximal. Cyclic somatostatin (a generous gift of Drs. Guillemin and Rivier) was intravenously infused for 2 to 3 hr at 0.4, 1.6, 6.2, 25, and 100 pg.kg-’ hrl. Some infusions were complemented with an initial single bolus injection corresponding to a l-hr dose. Each experiment involved 8 to 12 animals. Determinations. Sodium output was utilized as an index of pancreatic flow in acute fistula rats, because sodium concentration is constant (150 mEq per liter) in pancreatic juice.‘” Sodium was determined with flame photometry. A Technicon AutoAnalyzerlX was used to determine bicarbonate concentration. Total protein concentration was evaluated by absorbance at 280 nm. Results concerning sodium and bicarbonate outputs are expressed as their increased secretion (compared to basal levels) during the maximal stimulation by the particular agent. Protein outputs are expressed on a logarithmic scale, which enables homogenous variances to be maintained for minimal and maximal levels of secretion. The Student-Fisher t-test was used to determine the statistical significance of the results. The figures represent means + SEM.

C0$

a

0’ t

0

output

B

of basal

b

level

1

4

16

SRIF

,ug/kg/hr

62

25

0-I d

L

20

C03H 1

PEq

/hr

10

!

Proteinoutput s of basal

I

ievei

I

0

4

Protev

16

62

25

mg , 0,

r 1

r-l

Results Effects

of SRIF

on Basal Pancreatic

Secretion

Conscious rats. Pancreatic secretion in conscious rats is very high. ‘HI It underwent a dose-dependent decrease, beginning with the lowest dose of SRIF infused (fig. 1). An SRIF dose of 25 pg. kg-’ hr-’ depressed protein output (-80%) more than bicarbonate output (-63%) and flow (-42%). A poorly dose-dependent

FIG. 1. Somatostatin (SRIF)effectson basal pancreaticsecretions in consciousrats. a and b, dose-response curve corresponding to the maximal inhibition of SRIF on basal secretionsof bicarbonate (a) and protein (b). c and d, kinetic changes of basal secretions of bicarbonate (c) and protein (d) during and after a 2-hr infusion with SRIF at a dose of 6.2 gg.kg-’ hr’.

CHARIOT

ET AL.

Vol. 75, No. 5

nitude of these inhibitions, however, were lower than those observed for 2DG or electrical stimulation. Decreases of sodium and bicarbonate excretions were maximal (42 and 63%) for a dose of 100 pg. kg-’ hr-’ of SRIF (figs. 4 and 5), were not significant for this dose, and were poorly dose dependent. However, all SRIFtreated rata taken together had significantly lower electrolyte responses to acetylcholine than did controls. The maximal inhibition observed for protein output was 49% (P < 0.01) at a dose of SRIF of 25 r.cg.kg-l hr-l (fig. 6). ----

Na. PEqlhr 11 10 9

Control SRIF

a

L’ 5 4I+!! 3’ Protem mg/h 3-

FIG. 2. Effects of somatostatin (SRIF) on basal pancreatic secretions in anesthetized rata; 20-min fractions were collected. At time 0, both a bolus injection of a l-hour dose of SRIF and the beginning of SRIF infusion were performed. Upper panel represents the per cent variations of protein, sodium, and bicarbonate in relation to basal levels during the 0- to 20-min period. It can be seen that the effect is essentially stimulatory. Lower panel represents the effects observed during the 40- to 60-min period. At this time the effect is essentially inhibitory. No variations of the basal level occur in control animals not infused with SRIF.

variations occurring after the bolus and onset of infusion. Effects of SRIF on Stimulated Secretions Anesthetized Rats

in

Each stimulator-y agent was tested alone and in combination with various doses of SRIF (6.2 to 100 ~~g.kg-l hr-‘1. In order to reduce the quantity of data presented, we retained only those results corresponding to the dose of SRIF leading to the greatest effect upon each of the stimulations tested. ZDG. Infusions with SRIF inhibited BDG-stimulated secretions in a dose-dependent manner. The most effective dose of SRIF was 25 g-kg-’ hr-‘, which led to maximal inhibitions of 77% for sodium (P < 0.01; fig. 41, 84% for bicarbonate (P < 0.01; fig. 51, and 84% for protein (P < 0.01; fig. 6) outputs. Electrical stimulation of vagus nerves. Pancreatic responses to electrical stimulation of the vagus nerves were inhibited by SRIF infusions. This dose-dependent inhibition reached 70% for sodium (P < 0.01; fig. 4), 84% for bicarbonate (P c 0.01; fig. 5), and 85% for protein (P C 0.01; fig. 6) outputs with the most effective dose of 100 pg *kg-’ hr-‘. Acetylcholine. Infusions with SRIF inhibited pancreatic responses to exogenous acetylcholine. The mag-

I

_ ,__$_&_j_-__Y--~-----t--T--lI , , I,, ,

I,

1

I

t

1 SRIF I 25 pg

25I-‘g/kg/hr t

2. -____~___----~-----f--._--$___L______ l-

;

I-

I 1

5.420

20

0

40

60

80

100

ml” 120

FIG. 3. Kinetics of basal secretions of sodium and protein in pancreatic juice during an infusion with somatostatin (SRIF) at 25 pg. kg-’ hr’ combined with an initial injection of 25 M. kg-’ pg in anesthetized rata. A Na’ output 20 pEq/hr 0 Control =SRIF

I

I

15

10.

5,

“b 77 ..

0.

75 2ffi

El St

25 loo AcCh

.05

17 S

SO

330 HCI

FIG. 4. Sodium excretion observed in anesthetized rate with the somatostatin (SRIF) dose yielding the greatest inhibition of the stimulations obtained with 2-deoxy-n-glucose (2DG) at 75 mg. kg-l, electrical stimulation of the vagus (El St), acetylcholine (AcCh) at 25 and 100 pg.kg-’ min-I, secretin (S) at 0.05 to 0.50 clinical unit.kg-’ min-‘, and intraduodenal infusion with 330 FEq of HCl per hr. ANa+, increase of Na+ output over the basal level during the 20-min period of maximal stimulation. Figures above the columns represent the per cent inhibition by SRIF when it is significant in relation to controls not receiving SRIF. 00, P < 0.01 in relation to stimulation without SRIF.

SOMATOSTATIN

November 1978

AND PANCREATIC

A C03H output pEq/hr I

16 14

0 a

t

Control SRIF

12 10 1

8 t 6-

2DG

ElSt

h 330 HCI

S

A&h

FIG. 5. Bicarbonate excretion observed with the dose of somatostatin (SRIF) yielding the greatest inhibition of certain stimulations in anesthetized rats. AHC03-, increase in bicarbonate output over the basal level during the 20-min period of maximal stimulation. Other abbreviations as in figure 4.

Protem output ZOrmg/hr

10

I 2DG

0 Control ~SRIF I

ElSt

?-I49

AcCh

C-3?

FIG. 6. Protein excretion observed with the dose of somatostatin @RIFl yielding the greatest inhibition of certain stimulations in anesthetized rats. Cae, 5.5 to 50 ng. kg-’ min-’ of caerulein. 0, P < 0.05 in relation to stimulation without SRIF; other abbreviations as in figure 5.

During maximally effective infusions of SRIF, protein response to 2DG reached 1.35 mg per hr, and protein response to electrical stimulation reached 1.42 mg per hr (fig. 6). Both figures are significantly smaller than the response to acetylcholine, 25 pg * kg-’ hr-‘, which amounted to 2.9 mg per hr (P < 0.05), and than the response to acetylcholine 100 w*kg-’ hr-l which was 5.05 mg per hr (P < 0.001). In the absence of SRIF, the control responses to 2DG and electrical stimulation were similar to or greater than the response to 25 pg. kg-’ min-l of acetylcholine (fig. 6). Caerulein. The dose-response curve of pancreatic protein output to caerulein was shifled to the right during SRIF infusions (fig. 6). Inhibition was poorly dose dependent at the three SRIF doses used, 6.2,25, and 100 M. kg-’ hr-I. Caerulein had only mild effects on sodium and bicarbonate secretions under our conditions and SRIF effects on these parameters are not presented.

835

SECRETION

Exogenous secretin. The dose-response curves of SOdium and bicarbonate to exogenous secretin were not shifted by SRIF infusion, even at the highest dose of 100 pg.l@ hi-l (figs. 4 and 5). The effects of secretin on protein output were irregular and transient in this rat preparation; SRIF effects on this parameter were thus not retained. Endogenous secretin. Infusing SRIF led to only very slight decreases of pancreatic sodium and bicarbonate outputs in the presence of duodenal infusion of HCl. Because these responses were not significantly different from those noted in control groups not receiving SRIF (figs. 4 and 5), it may be concluded that the effect of SRIF on secretin release, if it exists, is negligible under the present conditions.

Discussion Published reports are in disagreement concerning the stimulatory effects of SRIF in vivo and in vitro,lE14 when most authors report inhibition of pancreatic exocrine secretion by SRIF. Our present results obtained in vivo seem to reconcile these opposing points of view, because both stimulation and inhibition were observed. The stimulatory effects we observed are apparently related to the bolus injection of relatively large quantities of SRIF, consistent with recent results obtained in rats after the administration of extremely large SRIF doses (500 pg per kg). lo The experiment involving 5-min fractions (fig. 3) shows that the observed stimulation is not a rebound effect attributable to the rapid clearing of a large dose of SRIF from the circulatory system. In addition, this effect could not be suppressed by atropine and so is not a cholinergic phenomenon. It has been suggested that the partial structural identity between somatostatin and the four amino acid residues in positions 5 to 8 of secretin may explain the secretin-like effect of the former. **The effects of exogenous secretin, however, were not changed by somatostatin and duodenal release was not modified, in agreement with the results of Bloom et al.* in pigs and Folsch et al.‘” in rats. The hypothesis that SRIF stimulation is related to its direct action on secretin receptors is rendered less plausible by these results. If this hypothesis were true, SRIF should act as a partial agonist of secretin. The effect of exogenous secretin would then have been partially inhibited, unless SRIF has a very low affinity for secretin receptors. Species differences do nevertheless exist, inasmuch as SRIF decreases secretin-stimulated bicarbonate and volume outputs in humans,“-’ dogs,1-3 and cats.4 SRIF also decreases the release of endogenous secretin in humans. 21 The slight inhibition by SRIF of caerulein effects on protein excretion indicates that there is a direct effect on acinar cells. Because this inhibition was practically dose independent, it was probably not related to a competition with caerulein for its binding sites. It may, however, result from an indirect effect of SRIF fixation on another site(s) on acinar cells. The inhibition of

836

CHARIOT ET AL.

CCK-PZ-stimulated enzyme output in rats has been reported,‘O but the doses of SRIF used, 500 and 1000 cLg *kg-’ hr-‘, were much larger than those utilized in the present study. Inhibition by SRIF of carbachol-stimulated pancreatic secretion has been described in man.22In rats, the effect of SRIF on the protein response to acetylcholine is similar to that on the response to caerulein and merits the same comments. Nevertheless, water and electrolyte responses to acetylcholine were decreased to some degree after SRIF administration. Because secretin effects were not depressed by SRIF, these results provide another argument indicating separate mechanisms for the effects of acetylcholine and secretin on fluid and electrolyte secretion in the pancreas. There is general agreement that duct cells are the main source of bicarbonate secretion in pancreatic tissue. l’Acinar cells may, however, also contribute to this secretion.23 Direct stimulation of fluid secretion by acetylcholine and electrical stimulation is generally admitted, at least in pigs,24rats,25-26and cats.n A direct effect of acetylcholine has been demonstrated on enzyme secretion in isolated acinar cells studied in vitro,28 and by electrophysiological methods in vitro and in vivo,2y but a choline&c effect on duct cells has neither been proved, nor definitely disproved. Physiological characteristics of fluid secretion stimulated by acetylcholine in the rat pancreas are different from those of secretin-induced fluid secretion, which involves cyclic CAMPY and necessitates extracellular HC03- in the isolated organ.% Thus, acetylcholine seems to act on fluid secretion by activating a mechanism different from the secretin mechanism. Because secretin acts primarily on duct cells, it is tempting to speculate that fluid secretion evoked by acetylcholine originates in acinar cells, as suggested for CCK-PZ23. However, one cannot eliminate the hypothesis of two separate mechanisms for fluid secretion in duct cells, and the site of action of acetylcholine on fluid and electrolytes remains undetermined. If the choline+ water and bicarbonate response originates in acinar cells, this implies that these cells, in which cholinergic receptors have been localized, can secrete water in quantities approaching 60 to 70% of the maximal response to secretin; this is the maximal response to acetylcholine observed in rats in vivo. 25 Central, preganglionic or peripheral stimulation of the vagal pathway shows that SRIF inhibition of 2DGor electrically-stimulated secretion is greater than that of secretion induced by acetylcholine. This suggests that inhibition by SRIF partially occurs at the effector site but is also localized in the vagal pathway to the pancreas. It is possible that some inhibition occurs at the pre- and/or postganglionic cholinergic fibers. This is consistent with the finding that SRIF decreases acetylcholine release in the electrically stimulated guinea pig ileum in vitro. lB Spontaneous flow of juice and enzymes was inhibited by SRIF more efficiently in conscious than in anesthetized rats. This difference is very likely to depend upon the different degrees of “basal” stimulation in both

Vol. 75, No. 5

models. In urethan-anesthetized rats, basal secretion is very low and is probably freed from most stimulatory hormonal and neural influences. I99%’In conscious rats with chronic deprivation of the pancreatic juice, the very large level of spontaneous secretion is likely to be attributed to neural and humoral factors potentiating each other. IV* 2oThus, SRIF has more sites to act upon in conscious rats, including pancreatic effector cells, acetylcholine release in the vagal outflow, and CCK-PZ release in the endocrine cells of the gut. REFERENCES 1.

BodenG,SivitzMC, Owen OE: Somatostatin suppresses secretin

and pancreatic exocrine secretion. Science 190:163-165, 1975 2. Konturek SJ, Tasler J, Obtulowicz W, et al: Effect of growth hormone release inhibiting hormone on hormones stimulating exocrine pancreatic secretion. J Clin Invest 581-6, 1976 3. Susini C, Pradayrol L, Bommelaer G, et al: Pancreatic effects of a partially purified duodenal somatostatin like immunoreactive peptide (SLI) (abstr). Ir J Med Sci 146(suppl):42, 1977. 4. Konturek SJ, Radecki T, Pucher A, et al: Effect of somatostatin on gastrointestinal secretions and peptic ulcer production in cats. Stand J. Gastroenterol12:379-383, 1977 5. Creutzfeld W, Lankisch PG, Folsch UR: Hemmung der Sekretinund Cholecystokinin-Pankreozymin-induzierten Saft- und Enzymsekretion des Pankreas und der Gallenblasenkontraktion beim Menschen durch Somatostatin. Dtsch Med Wochenschr 100:1135-1138, 1975 6. Dollinger HC, Raptis S, Pfeiffer EF: Effects of somatostatin on exocrine and endocrine pancreatic function stimulated by intestinal hormones in man. Horm Metab Res 8:74-78, 1976 7. Domschke S, Domschke W, Rosch W, et al: Inhibition by somatostatin of secretin-stimulated pancreatic secretion in man: a study with pure pancreatic juice. Stand J Gastroenterol 12:5963, 1977 a. Bloom SR, Joffe SN, Polak JM: Effect of somatostatin on pancreatic and biliary function (abstr). Gut 16:836-837, 1975 9. Folsch UR, Lankisch PG, Creutzfeld W: Effect of somatostatin on basal and stimulated pancreatic enzyme secretion and on stimulated volume and bicarbonate output in the rat. Eur J Clin Invest 6:314, 1976 10. Folsch UR, Lankisch PG, Creutzfeld W: Effect of somatostatin on basal and stimulated pancreatic secretion in the rat. Digestion 17:194-203, 1978 11. Dollinger HC, Raptis S, Goebell H, et al: Effect of somatostatin on gastrin, insulin, gastric and exocrine pancreatic secretion in man. In Stimulus Secretion Coupling in the Gastro-intestinal tract. Edited by RM Case, H Goebell. Lancaster, England, MTP Press, 1976, p 403-405 12. Albano JDH, Bhoola KD, Harvey RF: Effects of cholecystokinin and somatostatin on pancreatic enzyme secretion and tissue levels of cyclic GMP and cyclic AMP. Ir J Med Sci 146(suppll:2122, 1977 13. Albinus M, Case RM, Reed JD, et al: Effects of growth hormonerelease inhibiting hormone (GH-RIH or somatostatinl on secretory processes in stomach and pancreas. In Stimulus Secretion Coupling in the Gastro-intestinal Tract. Edited by RM Case, H Goebell. Lancaster, England, MTP Press, 1976, p 407-409 14. Deschodt-Lanckman M, Robberecht P, Pector JC, et al: Effects of somatostatin on pancreatic exocrine function. Interaction with secretin. Arch Int Physiol Biochim 83:960-961, 1975 15. Guillemin R: Somatostatin inhibits the release of acetylcholine induced electrically in the myenteric plexus. Endocrinology 99:1653-1654,1976 16. Roze C, La Tour J de, Chariot J, et al: Technique d’etude de la secretion pancreatique externe chez le rat. Biol Gastroenterol

November 1978

SOMATOSTATIN

AND PANCREATIC

(Paris) 8:291-295, 1975 17. Singh M, Webster PD: Neurohormonal control of pancreatic secretion. A review. Gastroenterology 74:294-309, 1978 18. Chariot J, Roze C: Determination automatisee de tres faibles concentrations de bicarbonates. Application au sue pancreatique. Ann Biol Clin (Paris) 34:269-272, 1976 19. Chariot C, Raze C, La Tour J de, et al: La secretion pancreatique chez le rat. Etude comparative des secretions basales et stimulees en tistule aigue et chronique Path01 Biol (Paris) 24:457-461, 1976 20. Petersen H, Grossman MI: Pancreatic exocrine secretion in anesthetized and conscious rats. Am J Physiol 233:E530-E536, 1977 21. Hanssen LE, Hanssen KF, Myren J: Inhibition of secretin release and pancreatic bicarbonate secretion by somatostatin infusion in man. Stand J Gastroenterol 12:391-394, 1977 22. Lankisch PG, Arnold R, Creutzfeld W: Wirkung von Somatostatin auf die Betazol Stimulierte Magensekretion und die Carbachol stimulierte Pankreassekretion und Gallenblasenkontraktion des Menschen. Dtsch Med Wochenschr 100:1797-1800, 1975 23. Folsch UR, Creutzfeld W: Pancreatic duct cells in the rat: secretory studies in response to secretin, cholecystokinin-pancreozymin, and gastrin in vivo. Gastroenterology 73:1053-1059,

SECRETION

837

1977 24. Hickson JCD: The secretion of pancreatic juice in response to stimulation of the vagus nerves in the pig. J Physiol (Land) 216:303-318, 1971 25. Debray C, La Tour J de, Vaille C, et al: Action de l’acetylcholine sur la secretion pancreatique externe du rat: cinetique et relation dose-effet. Biol Gastroenterol (Paris) 5:61-70, 1972 26. Petersen OH, Ueda N: Secretion of fluid and amylase in the perfused rat pancreas. J Physiol (Lend) 264:819-835, 1977 27. Lenninger S, Ohlin P: The flow of juice from the pancreatic gland of the cat in response to vagal stimulation. J Physiol (Land) 216:303-318, 1971 28. Gardner JD, Conlon TP, Klaeveman HL, et al.: Action of cholecystokinin and cholinergic agents on calcium transport in isolated pancreatic acinar cells. J Clin Invest 56:366-375, 1975 29. Petersen OH, Ueda N: Pancreatic acinar cells: effect of acetylcholine, pancreozymin, gastrin and secretin on membrane potential and resistance in vivo and in vitro. J Physiol (Land) 247:461-471, 1975 30. Folsch UR, Creutzfeld W: Electrolyte secretion by a pancreatic duct model in the rat in vivo and accumulation of CAMP in vitro in response to gastrointestinal hormones. In Stimulus Secretion Coupling in the Gastrointestinal tract. Edited by RM Case, H Goebell. Lancaster, England, MTP Press LTD, 1976, p 381-384