John W. Borner

Pancreatitis as a complication of anticholinesterase insecticide intoxication.

Severe pancreatitis and a pseudocyst occurred in a patient following accidental ingestion of an anticholinesterase insecticide, a substance not previously known to produce pancreatitis. Experiments were done to elucidate the mechanism. In one group of dogs the pancreatic duct was perfused and intraductal pressures were measured. The cholinesterase inhibitor 0,0-diethyl-0-(2-isopropyl-6-methyl-4-pyriinidinyl)phospborothioate (25 mg/kg) caused a significant increase in the mean intraductal pressure from 12 ± 2.4 to 27.8 ± 5.9 cm saline. In a second group of dogs pancreatic secretory rates were measured. Anticholinesterase (75 mg/kg) in combination with secretin infusion (1 U/kg/hr) caused a significant increase in the secretin stimulated flow rate from 0.13 to 0.56 cc/min. Atropine (75 μg/kg) abolished the anticholinesterase induced pressure and secretory rate increases. In a third group of dogs administration of cholinesterase inhibitor 75 mg/kg and secretin infusion 2 U/kg/hr resulted in acute pancreatic interstitial edema, acinar cell vacuolization, hyperamylasemia and hyperlipasemia. These results suggest that occurrence of pancreatitis as a complication of anticholinesterase insecticide intoxication is the result of hypersecretion and pharmacologie ductal obstruction.

The effect of atropine and duct decompression on the evolution of Diazinon-induced acute canine pancreatitis.

Three groups of eight dogs each were studied to evaluate the early evolution of the hyperamylasemia, hyperlipasemia, and acinar cell pathology at the light and electron microscopic levels during acute Diazinon-induced pancreatitis. Two more groups of five dogs each were evaluated for the effects of cholinergic receptor blockade with atropine and ductal decompression on the evolution of serum enzyme changes and acinar cell pathology. Group I dogs received a secretin infusion of 2 units/kg/hr, and a Diazinon infusion of 75 mg/kg, and demonstrated significant increases in serum amylase and lipase at one, two and three hours. Light microscopy revealed acinar cell vacuolization and progressive interstitial edema. Electron microscopy revealed the formation of large intracytoplasmic vacuoles filled with flocculent material, the fusion of these vacuoles with basolateral membrane, and the formation of interstitial edema. In both group II dogs (that received secretin alone) and Group III dogs (that received atropine, 200 micrograms/kg IV prior to secretin and Diazinon), the serum enzyme levels and histologic results were normal. In group IV dogs, pancreatic duct cannulation to prevent hypertension prevented the hyperamylasemia and hyperlipasemia, but not the acinar cell vacuolization and interstitial edema. This model for acute interstitial pancreatitis is apparently cholinergic-receptor mediated, the serum enzyme elevations are due primarily to ductal hypertension, and the acinar cell pathology is primarily due to cholinergic stimulation and occurs independent of ductal hypertension.

Gastric blood flow

Summary The role of gastric distention in regulating blood flow and its distribution within the gastric microcirculation was determined by the radiorubidium clearance technic. Gastric distention produces a profound and selective reduction in blood flow to the mucosa and submucosa of the corpus without altering blood flow to the adjacent muscularis. It is suggested that these changes in gastric blood flow result from lengthening and narrowing of the submucosal vessels of the distended corpus.

Sensitivity of the Canine Pancreatic Intraductal Pressure to Subclinical Reduction in Cholinesterase Activity

As a continuation of work from this laboratory on anti-cholincsterasc induced pancreatitis, a study of the relationship between reduced scrum cholinesterase activity and changes in pancreatic intraductal pressure was undertaken. Pharmako-kinetic studies in three dogs revealed rapid reduction in serum cholinesterase activity following an IV bolus dose of the cholinesterase inhibitor 0,0-diethyl-0-(2-isopropyl-6-methyl-4-pyrimidinyl)phosphorothioate. Following each dose of cholinesterase inhibitor, stable levels of cholinesterase inhibition were reached in 30 minutes. In four dogs the pancreatic duct was perfused from the tail of the ventral pancreas and intraductal pressures measured. A total of 25 mg/kg of the cholinesterase inhibitor was given in 5 mg/kg doses 30 minutes apart, and scrum cholinesterase measured 30 minutes after each dose. Mean pressures were established over a 15 minute interval. Linear regression analysis of 23 data points revealed a significant (p < 0.001) cumulative dose-related increase in pancreatic intraductal pressure [Pressure (cm saline) = 14.2 + 1.03 × Cumulative Dose (mg/kg)] and significant (p < 0.001) negative correlation between serum cholinesterase activity and intraductal pressure [Pressure (cm saline) = 48.0 − 0.057 × Esterase Activity (mU/ml)]. These data suggest that, in dogs, reduced cholinesterase activity is directly related to increased pancreatic intraductal pressure, and it may be a factor in the pathogencsis of pancreatitis.

Organophosphate increases the sensitivity of human exocrine pancreas to acetylcholine.

Human pancreas contains two cholinesterase isoenzymes: acetyl-cholinesterase (AChE) and butyrylcholinesterase (BuChE). In the present study, binding potency of two organophosphates for human cholinesterases were compared by the Ellman method. Echothiophate was found to have much greater potency than iso-OMPA for both cholinesterases. Using Karnovsky histochemical stains on human pancreatic tissue, the same results were confirmed. Dose-response studies with acetylcholine were done on viable pancreas fragments from nine human donors, without pancreatic disease (group I). Cold-preservation time was less than 30 h. Pancreas was minced into fragments, after the technique of Scheele and Palade, placed in Eagles medium, and gassed with 0. Amylase release was measured by the Phadebas Method and corrected for basal release. There was a dose-dependent response to acetylcholine at 1 and 2 h, with a shift in peak amylase release to the left, when fragments were preincubated in 10−4 M echothiophate. This indicated a 100-fold increase in sensitivity to acetylcholine. In three patients with chronic pancreatitis (Group 11), there were variable patterns of response of amylase release to acetylcholine, and higher basal outputs. In Group 111, prolonged storage conditions of over 40 h were tested for 4 pancreas donor tissues. There was no response to acetylcholine. These studies show that for up to 30 h cold storage, fragments of pancreas from human organ donors respond to acetylcholine in dose-dependent manner. An organophosphate, echothiophate (10−4 M) which inhibits both cholinesterases, increases pancreatic sensitivity to acetylcholine, and these results are similar to findings from canine pancreas fragments, which also showed increased sensitivity.

A study of the cholinesterases of the canine pancreatic sphincters and the relationship between reduced butyrylcholinesterase activity and pancreatic ductal hypertension.

Previous work from this laboratory revealed in increased canine pancreatic intraductal pressure following cholinesterase inhibitor intoxication. The pressure was negatively correlated with serum butyrylcholinesterase (BChE) activity, suggesting that BChE activity mediated the pressure rise. This study uses a histochemical technique to investigate the tissue cholinesterase activity of the canine pancreatic sphincters and the effect of a cholinesterase inhibitor (ChEI) on tissue cholinesterase activity. In five control dogs, serial sections of the major and minor spincters were stained for acetylcholinesterase (AChE) and BChE activity. Four treated dogs were given the ChEI, O,O-diethyl-O- (2-isopropyl-6-methyl-4-pyrimidinyl) phosphoro-thioate, 25 mg/kg, one hour prior to excising the ampullae. In the control dogs, BChE activity is present in the periampullary nerves and the pancreatic smooth muscle sphincters. AChE activity is present in nerves but not in smooth muscle. In the treated group, following a dose of ChEI known to cause ductal hypertension, BChE activity was absent in the pancreatic sphincters but AChE activity was preserved in the periampullary nerves. These data suggest that the pancreatic ductal hypertension that occurs following ChEI administration is due to a selective reduction in pancreatic smooth muscle BChE activity.

Clinical and secretory differences in pancreatic cancer and chronic pancreatitis.

The differential diagnosis between chronic pancreatitis and pancreatic cancer can be very difficult. In 60 patients with either of these conditions, who had satisfactory ERCP study, clinical features were correctly matched with the final diagnosis by discriminant analysis in 44 (73%). The sensitivity of ERCP radiographic findings in pancreatic cancer was 80% and sensitivity of cytology was 54%. To see if exocrine function was specific for cancer, fresh pancreatic secretions were aspirated in 27 patients at the time of ERCP. By isoelectric focusing, a pattern of extreme zymogen depletion was observed in chronic alcoholic pancreatitis (Group 1), pancreatic cancer (Group 2), and chronic nonalcoholic pancreatitis (Group 3). The three groups were not distinguishable. By contrast, significant changes in albumin, IgG and IgA concentrations were seen in Group 2. The albumin level was over ten-fold greater than in Groups 1 and 3 (p ≤ 0.02 and ≤0.05). The IgG was sevenfold and two-fold greater (p ≤ 0.01 and ≥0.2) and the IgA was 15-fold and six-fold greater (p ≤ 0.002 and ≤0.05) than in Groups 1 and 3, respectively. The two groups of pancreatitis had similar concentrations of albumin and IgA. The ratio of albumin to IgG was also different in Group 2 from the other groups, suggesting different mechanisms for the appearance of proteins in pancreatic secretions. Nonzymogen protein levels can distinguish chronic pancreatitis from pancreatic cancer, and further study of them may identify useful tumor-specific markers

Increased canine pancreatic acinar cell damage after organophosphate and acetylcholine or cholecystokinin.

Sublethal doses of organophosphate anticholinesterases cause acute pancreatitis in dogs within 2 h. In vitro studies using canine pancreatic fragments have also demonstrated that the peak of amylase release in response to acetylcholine is shifted far to the left after incubation with the organophosphates echothiophate (10−4M) or tetraisopropyl pyrophosphoramide (iso-OMPA) (10−3M), indicating an increased sensitivity of response The present in vitro study examined whether there was also an increased susceptibility to acinar cell damage at the electron microscopic level after acetylcholine or cholecystokinin. Minced pieces of whole fresh canine pancreas 2–3 mm in size were placed in buffered Eagles solution and gassed with 100% O2. After pretreatment 1 h with echothiophate or iso-OMPA, they were then incubated with acetylcholine (10−5M). Other tissues preincubated with echothiophate were stimulated with cholecystokinin (10−9M). These are submaximal doses for untreated canine pancreatic fragments. After acetylcholine and echothiophate or acetylcholine and iso-OMPA, there was extensive acinar damage with the appearance of large vacuoles and lakes, and interstitial edema. There was evidence of intense supramaximal stimulation and lateral exocytosis. Similar destructive changes were seen after echothiophate and cholecystokinin. In control sections from tissues stimulated with acetylcholine (10−5M) or cholecystokinin (10−9M), there were lumenal exocytotic patterns typical of submaximal stimulation. Other controls, organophosphate alone and unstimulated basal conditions, showed only minor changes. It is concluded that the increased sensitivity to acetylcholine after organophosphate incubation correlates with an increased susceptibility to acinar ultrastructural damage from acetylcholine and cholecystokinin.

Effect of the organophosphate iso-OMPA on amylase release by pancreatic lobules of dog, guinea pig, and cat

Organophosphates (OPs) cause irreversible inhibition of cholinesterases (ChEs) and profound cholinergic stimulation. There are major differences in the response of the dog and cat pancreas to the in vivo administration of Diazinon (0,O-diethy1 0-2-isopropy1-4-methy1-6-pyrimidyl phosphothioate), a butyrylcholinesterase (BuChE) inhibitor. Acute edematous pancreatitis is found in the dog but not in the cat. The present experiments were designed to see what effect OP had in vitro on pancreatic exocrine function of dog, cat, and guinea pig, and whether the effects were consistent with an anti-ChE activity. A water-soluble OP agent, tetraisopropyl pyrophosphoramide (iso-OMPA) at M, which like Diazinon inhibits BuChE, was used. Minced pieces of fresh whole pancreata 3 mm in size were taken from 3 dogs, 4 guinea pigs, and 2 cats. The tissues were placed in flasks containing Eagles solution and gassed with 100% 02. Cumulative amylase release was measured by Phadebus method up to 3 h. At half-maximal acetylcholine (ACH) concentration M) showed a 42-87% greater release of amylase than tissues receiving ACH alone (p <0.001). The same potentiated response to ACH was seen in guinea pig pancreas pretreated with iso-OMPA (p <0.001), but iso-OMPA pretreatment did not augment the ACH response in the cat. Atropine pretreatment effectively blocked all ACH responses, and there was no effect seen with iso-OMPA alone. In the dog, iso-OMPA in combination with half-maximal carbachol (10−6M), or in combination with half-maximal cholecystokinin (CCK-8) stimulation (10−9M), provided no potentiated amylase release. BuChE is normally present in dog and guinea pig acinar cells, but is lacking in cat acinar cells. We conclude that OPs such as iso-OMPA cause a potentiated exocrine response to ACH in vitro and this effect can be satisfactorily explained by an anti-BuChE activity. Our results do not identify a mechanism relating the heightened cho linergic exocrine response to pancreatic toxicity.

Hyperplasia of pancreatic duct epithelium produced by exposure to sodium deoxycholate

Severe epithelial hyperplasia was produced in a canine model by the perfusion of the main pancreatic duct with 15 mM of deoxycholate at rates as low as 1.5 ml/day in 6 to 14 days. At higher rates (5 ml/day) deoxycholate caused complete epithelial cell lysis in the duct closest to the tip of the cannula with hyperplastic changes downstream from this section. Perfusion with a buffer solution alone and cannulation alone produced none of these changes in similar duct segments. No hyperplasia was seen in the upstream cannula obstructed duct, even in the presence of severe atrophy. Long-term (81 days) perfusion with 3 mM of deoxycholate at 3 ml/day resulted in more severe hyperplasia that still appeared benign. When glycine-conjugated deoxycholate was perfused through the duct, hyperplasia but no cell lysis was seen. In vitro, deoxycholate caused epithelial cell lysis in pancreatic duct fragments at concentrations of 0.5 mM and above. The results of this study suggest that secondary bile salts or other similar surface-active cytotoxic agents present in the biliary tree or duodenum may play a more important role in the pathogenesis of pancreatic ductal epithelial hyperplasia associated with pancreatic cancer than ductal obstruction.