The aging process.

The intricate cause of the aging process in humans and animals, at present a matter of intense speculation, has given rise to many theories. Despite its uncertain cause, aging constitutes the most significant and universal problem confronting physicians today. Age-related physiologic deterioration and age-associated diseases are of immense concern to physicians because of the "old-age boom" anticipated in the first part of the twenty-first century. Biomedical research achievements in the twentieth century have permitted more persons to approach the fixed upper limit of the human lifespan. We discuss the functional decline of the aging heart and the underlying mechanisms of that decline; quantitative and qualitative changes in the immune system; and normal aging of the human brain contrasted to the brain changes seen in Alzheimer disease. With our growing geriatric population, we greatly need to increase our understanding of both the causes of human aging and the goals of gerontology and geriatrics and to expand research into the significant problem of Alzheimer disease.

Dynamic changes of pancreatic structure and function in rats treated chronically with nicotine.

Adult, male Sprague-Dawley rats weighing initially 185-225 g, were treated with 5, 15, or 50 mg nicotine or placebo 3-week-release pellets by sc implantation, for 1.5, 3, 6 and 12 weeks. These doses of nicotine correspond to infusion rates of 9.9, 29.8, and 99.2 micrograms/h, respectively. At the highest nicotine dose trypsin and chymotrypsin activities were markedly higher in pancreas from 12-week nicotine-treated rats compared with controls. This was associated with a fourfold increase in steady-state amylase mRNA levels in comparison to placebo controls. In addition, secretagogue-stimulated enzyme release from pancreatic acini isolated from rats treated with 50 mg nicotine pellets was significantly higher than controls at 1.5 and 3 weeks and declined below control levels after 12 weeks of treatment. In rats treated with 15-mg nicotine pellets, maximal secretagogue-stimulated enzyme release from isolated acini occurred at 1.5 weeks, declining thereafter to control levels. Electron microscopy of pancreas from rats treated with the 50 mg nicotine dose revealed intracytoplasmic vaculoes appearing after 3 weeks of treatment, and persisting throughout the remaining experimental period. It is concluded that 12-week nicotine treatment results in increased pancreatic enzyme biosynthesis and accumulation of digestive enzymes within the pancreas. This is associated with altered responsiveness to secretagogues and evidence of morphological damage.

Proteolytic degradation of human recombinant proinsulin/insulin by sera from acute pancreatitis patients and complete inhibition by Eglin-C.

Sera from patients of biliary, alcoholic, and idiopathic acute pancreatitis with severity scored from 1 to 5 based on the Ranson criteria were tested for proinsulin/insulin degrading activity. Proinsulin degrading activity by normal controls was 8 +/- 4% as compared with 22-78 +/- 17% with a mean of 45% by the patient sera. An order of magnitude increase of proinsulin degrading activity was accompanied by an order of magnitude increase of immunoreactive pancreatic cationic trypsin(ogen) and (pro)elastase-2 as determined by radioimmunoassay with day 1 sera. Proinsulin degrading activity also showed a negative correlation with the clinical time course and dropped to normal by 6 days after admission. The decrease of proinsulin degrading activity was concomitant with a decrease of serum immunoreactive pancreatic serine proteases. High-performance liquid chromatography analysis of the proteolysis products showed the appearance of insulin and smaller peptides with no proinsulin conversion intermediates. Ninety to ninety-eight percent of proinsulin degrading activity was inhibited by anti-alpha 2-macroglobulin (alpha 2-M) antiserum, or (Ac)Eglin-C(J141), and 52% by an elastase and chymotrypsin-specific inhibitor, MeOSuc-Ala-Ala-Pro-boroVal-pinacol. E64c, TLCK, alpha 1-protease inhibitor (alpha 1-PI), or Trasylol inhibited proinsulin degrading activity by 10-17%, and anti-cathepsin B antiserum by 9%. The observed proinsulin degrading activity did not correlate with the Ranson's scores, age, sex, etiology, total serum immunoreactive insulin, calcium, albumin or alpha 2-M but had a negative correlation with serum alpha 1-PI (r = -0.55) and a positive correlation with serum esterase activity (r = .62).(ABSTRACT TRUNCATED AT 250 WORDS)

Recruiting students for medicine.

The applicant-to-acceptance ratio in the nation's 127 medical schools has slowly but steadily declined during the last decade to 1.7:1 (60.5% acceptance rate) for the 1987-1988 academic year. The 28,123 applicants in this academic year represent a decrease of 3200 applicants from the previous year. The decline in the number of applicants is even more striking because it occurred despite the welcome increase of female applicants between 1965 to 1988 (36% of the entering class in the 1987-1988 academic year). The laudable changes in the Medical College Admission Test (MCAT) examination, which take effect in 1991, will not solve this problem. We believe that the causes of the flight away from medicine as a career are several and represent the combined effect of changes in the practice of medicine itself and their negative impact on the profession, as well as deeply-seated shifts in values, attitudes, and aspirations among the young people in our society. We discuss several factors concerning the phenomenon in question and offer some suggestions concerning solutions for this important problem. Our goal in this brief essay is to stimulate discussion and awareness among physicians concerning medical school admissions and to galvanize into action the medical profession and other key persons who are keenly interested in high-quality health care for our people.

Altered exocrine pancreatic function in rats treated with nicotine.

The present study investigates the effects of nicotine treatment on exocrine pancreatic function. Adult male, Sprague-Dawley rats received nicotine via a time-release pellet, at a rate of 1.65 micrograms/min for 3 weeks. At the end of the experimental period, it was observed that although nicotine did not affect final body or pancreatic weight, the activities of amylase, trypsin, and chymotrypsin in pancreatic homogenates from nicotine-treated rats were 51, 29, and 35% higher, respectively, than in controls. Levels of immunoreactive cationic trypsin(ogen) were significantly higher in pancreatic homogenates and serum from nicotine-treated rats as compared with controls. In addition, concentrations of mRNA, encoding for pancreatic amylase, were higher in pancreatic homogenates from the nicotine-treated rats than in controls. In dispersed pancreatic acini isolated from nicotine-treated rats, basal secretion of amylase, trypsinogen, and chymotrypsinogen was 50% higher than controls and enzyme release following CCK-8 (100 pM), secretin (1 microM), and carbachol (7.5 microM) stimulation was also significantly higher. These data indicate that nicotine treatment, at levels comparable to those expected in moderate cigarette smokers, increases the content of digestive enzymes in rat pancreas, as well as their basal and secretagogue-induced release.

Assessment of the role of pancreatic proteases in human abdominal aortic aneurysms and occlusive disease.

Previous studies on the pathogenesis of abdominal aortic aneurysms have shown both elastase-like activity in the aortic wall and a decreased elastin content. The present study, using specific radioimmunoassays for pancreatic elastase 2 (IRE2) and cationic trypsin(ogen) (IRCT), investigates the concentrations of these proteases which are known to circulate in blood, in abdominal aortic aneurysms. Aortic specimens were obtained from 32 patients with aneurysms and 21 patients with atherosclerotic occlusive disease. Aortic tissue, obtained at autopsy from young adults, served as controls. Elastase-like activity was 300% and 800% higher, respectively, in aortic homogenates from aneurysms in comparison to occlusive disease and control aortic tissue. This was associated with 1.4-fold higher level of IRE2 and 2.7-fold higher levels of IRCT as compared to occlusive disease. Although there was no significant difference in the aortic collagen concentration among all 3 groups, the elastin content of aneurysmal aorta was 85% and 74% lower, respectively, in comparison to control and occlusive aorta. The results of this investigation demonstrate the presence of pancreatic elastase 2 and cationic trypsin(ogen) in abdominal aortic aneurysmal tissue and suggest that circulating pancreatic proteases contribute to the pathophysiology of aneurysms of the infrarenal aorta.

Pseudomonas aeruginosa cytotoxin stimulates secretion of amylase and protease zymogens with a concomitant decrease of mRNA levels in isolated rat pancreatic acini.

The action of Pseudomonas aeruginosa cytotoxin on isolated pancreatic acini was investigated. The release of amylase and serine protease zymogens from the isolated rat pancreatic acini was induced with increasing amounts of cytotoxin in vitro. The stimulated release of amylase reached 30% of total cellular content with 100 micrograms/mL of the purified cytotoxin. The induced release of amylase, trypsinogen, proelastase, and chymotrypsinogen reached the maximum after 75 minutes of incubation while lactate dehydrogenase began to appear after 15 minutes of incubation with a secondary biphasic increase at 75 min of incubation. The concentrations of acinar mRNAs of amylase, trypsinogen, proelastase, and chymotrypsinogen, as measured by dot-blot hybridization with the cloned cDNAs of amylase, trypsinogen I, proelastase II, and chymotrypsinogen B of the rat, decreased with time and were significantly lower than in the untreated acini. It is concluded that cytotoxin stimulates the release of amylase and protease zymogens with a concomitant increase in membrane permeability and a decrease of cellular mRNA levels. The inhibition of gene expression is attributable merely to a generalized toxic effect upon cellular metabolism.

Secretagogue-induced enzyme release from the exocrine pancreas of rats following adaptation to a high protein diet.

The mechanisms of pancreatic adaptation to dietary changes and whether these changes are reflected in the serum are not fully understood. The present study investigates secretagogue-induced release of digestive enzymes from dispersed pancreatic acini as well as the concentrations of these enzymes in serum and pancreas after adaptation to a high protein diet. Adult rats were fed an 8.5% casein diet ad libitum. After 14 d the rats were divided into three groups and fed isoenergetic diets constituting 8.5, 24 or 40% protein for an additional 6 d. No significant differences in final body weight or pancreatic weight were observed among the groups of rats. Rats adapted to the 40% protein diet showed significantly higher trypsin and chymotrypsin activity in pancreatic homogenates than rats fed the 8.5% protein diet. These changes in pancreatic enzyme content were not reflected in serum. Pancreatic acini isolated from the 8.5% protein group showed a markedly reduced responsiveness to cholecystokinin (CCK-8), secretin- and carbachol-induced enzyme release in comparison to the other two dietary groups, although basal enzyme release was the same in all groups. These results indicate that the secretion of pancreatic enzymes following a physiological stimulus is affected by a low protein, high carbohydrate diet.

Biochemical studies in peritoneal fluid from patients with acute pancreatitis. Relationship to etiology.

The levels of pancreatic digestive enzymes, lysosomal hydrolases, and protease inhibitors were evaluated in ascites fluid from 24 patients with acute pancreatitis diagnosed as alcoholic, gallstone-induced, or idiopathic. In this group the concentrations of amylase (354 +/- 98 ng/ml), immunoreactive cationic trypsinogen (1840 +/- 238 ng/ml), and immunoreactive elastase 2 (1492 +/- 262 ng/ml) were greatly elevated in comparison to the corresponding serum values. Enzyme levels in ascites from the idiopathic pancreatitis group tended to be higher than the levels from the other two groups. Activity of acid phosphatase and beta-glucuronidase was significantly higher in ascites compared to serum in all groups. On the other hand, levels of immunoreactive alpha 1-protease inhibitor and alpha 2-macroglobulin in ascites fluid were about half the average concentrations reported for normal serum. Significant amounts of tryptic amidase activity (61.7 +/- 13.7 micrograms/ml) were observed, indicating a trypsin-alpha 2-macroglobulin complex. These data indicate an imbalance in the protease-to-inhibitor ratio in ascites fluid from patients with acute pancreatitis. Coupled with elevated ribonuclease activity (27.4 +/- 3.4 units), a positive methemalbumin test in 23 of 24 patients (1.1 +/- 0.4 mg hematin/100 ml), and an average protein concentration of 4.0 +/- 0.2 g/100 ml, these observations demonstrate that abdominal paracentesis and the biochemical analyses of ascites fluid provide useful information related to the biochemical events in acute pancreatitis and may be useful in the diagnosis of difficult cases, but their predictive value of severity remains to be established.

Raised serum concentrations of pancreatic enzymes in cigarette smokers.

Circulating concentrations of digestive enzymes, certain lysosomal hydrolases and protease inhibitors were measured in 19 heavy smokers and 13 non-smokers before (basal) and at 15, 30, and 60 minutes after a single intravenous injection of secretin (75 CU). In smokers, basal serum amylase and immunoreactive pancreatic elastase 2 (IRE2) concentrations were about 100% and 25% higher respectively, than in the non-smokers, whereas, no differences were observed in basal immunoreactive cationic trypsinogen (IRCT) concentrations and in acid phosphatase and beta-glucuronidase activities between the two groups. Furthermore, a single injection of secretin to cigarette smokers significantly increased serum amylase, IRCT and IRE2 by 155%, 200%, and 100%, respectively when compared with their corresponding basal levels. No such increment was observed in the non-smokers. In addition, there were no significant differences in serum trypsin or elastase inhibitory capacity or immunoreactive alpha 1-protease inhibitor and alpha 2-macroglobulin levels between smokers and non-smokers. The levels and inhibitory capacity of these protease inhibitors was also not affected by secretin injection. These data suggest that cigarette smoking enhances the responsiveness of the exocrine pancreas to a physiological stimulus such as secretin, with resultant substantial increase in the concentrations of pancreatic hydrolases in blood.

Digestive enzymes and protease inhibitors in plasma from patients with acute pancreatitis.

The plasma levels of certain digestive enzymes and protease inhibitors were determined in 40 patients with severe acute pancreatitis diagnosed as gallstone-induced (GP), alcoholic (AP), or idiopathic (IP). On admission, plasma levels of amylase and immunoreactive cationic trypsin(ogen) (IRCT) and elastase 2 (IRE 2) were found to be 50 +/- 10 ng/ml, 340 +/- 64 ng/ml, and 190 +/- 15 ng/ml, respectively, in all groups of patients. These enzymes levels remained high for the first 2 days following hospitalization and then decreased, although amylase and IRCT levels remained elevated above normal values throughout the study period (2 weeks). In general amylase and IRCT were lower in patients with concomitant ascites, pancreatic pseudocysts, or abscesses, and higher in patients who died, as compared to the pancreatitis group as a whole. In these patients, levels of immunoreactive alpha 1-protease inhibitor (alpha 1-PI) and alpha 2-macroglobulin (alpha 2-M) remained relatively constant at the lower end of the normal range throughout the study period. Inhibitor levels in plasma were unaffected by the etiology of pancreatitis or the occurrence of complications. A similar trend was seen with plasma levels of lysosomal hydrolases. The results indicate that in this group of patients, plasma levels of pancreatic digestive enzymes were reflective of the clinical features and severity of the disease, as well as the time following the acute attack that brought the patient to the hospital.

Stimulation of enzyme secretion from isolated pancreatic acini by Clostridium difficile toxin B.

Exposure of isolated rat pancreatic acini to increasing concentrations (10 ng - 800 ng/ml) of toxin B from Clostridium difficile produced a biphasic effect on the rate of secretion of amylase, trypsinogen, and chymotrypsinogen. Whereas doses of toxin B from 10-30 ng/ml increased enzyme secretion by 15-20%, doses between 30 ng and 60 ng/ml showed a regression of this effect, whereafter the rate of secretion of amylase, trypsinogen, and chymotrypsinogen increased with increasing concentrations of the toxin. Toxin B concentration of 800 ng/ml enhanced amylase, trypsinogen and chymotrypsinogen secretion by 119%, 185% and 195%, respectively, when compared with the basal level. Stimulation of enzyme secretion by toxin B was not affected by the presence of either actinomycin-D or cycloheximide, at a concentration which inhibited acinar RNA or protein synthesis by 80-90%. Although toxin B as well as CCK8, carbachol and secretin by themselves caused significant stimulation in amylase, trypsinogen and chymotrypsinogen secretion from isolated pancreatic acini, toxin B together with either CCK8, carbachol or secretin produced no further augmentation in enzyme secretion than what was observed with the secretagogues alone. It is concluded that toxin B of Cl. difficile exerts a direct effect on pancreatic acinar cells as evidenced by stimulation of enzyme secretion.

Evaluation of the role of calcium in cytotoxic injury in isolated rat pancreatic acini.

The role of extracellular Ca2+ in pancreatic acinar membrane damage (cellular injury) by nicotine, membrane-active agents (mellitin, snake venom and Ca2+ ionophore A23187) and secretagogues (CCK-8 and secretin) was investigated. Freshly isolated dispersed pancreatic acini from 18 h fasted adult rats were incubated with one of the aforementioned agents, in the absence and presence of Ca2+. Cellular injury was assessed by measuring the release of pulse-labeled 51Cr and LDH. In addition, release of amylase, trypsinogen and chymotrypsinogen was also determined. In the absence of Ca2+ nicotine (6 mM) caused a profound release of 51Cr and LDH as well as amylase, trypsinogen and chymotrypsinogen from the isolated pancreatic acini. Release of these enzymes and 51Cr decreased sharply with addition of increasing concentrations (0.25-5 mM) of Ca2+. Release of 51Cr and amylase by snake venom (50 micrograms/ml) was found to be 100 and 25% higher, respectively, in the absence of Ca2+ than in its presence. On the other hand, the Ca2+ ionophore A23187 (7 micrograms/ml) was found to be effective in releasing 51Cr and amylase only in the presence of Ca2+. CCK-8, (0.25nM), secretin (1 microM) and mellitin (0.5 microgram/ml) although significantly stimulated amylase secretion (225-350%) in the presence of Ca2+, none of the agents induced 51Cr release from acini, either in the absence or in the presence of extracellular Ca2+. It is concluded that the extracellular Ca2+ plays no specific role in cytotoxic injury in isolated pancreatic acini.

Morphological and biochemical changes of the pancreas in rats treated with acetaldehyde.

Daily intraperitoneal injections of acetaldehyde for 10 days to adult rats produced distinct morphological and biochemical changes in the exocrine pancreas, without affecting the body weight, pancreatic weight, and DNA, RNA, and protein content of the pancreas. By electronmicroscopy, although the number and size of the acinar zymogen granules appeared to be the same between the saline- and acetaldehyde-treated rats, the zymogen granules of the latter group showed decreased osmiophilia. Acinar mitochondria of the acetaldehyde-treated rats were found to be slightly swollen with dense granules, and plasma membrane fragments were often seen in the acinar lumen. Administration of acetaldehyde significantly decreased immunoreactive cationic trypsin (ogen) and total amylase activity in the pancreas, but not in the serum, where amylase activity was markedly increased. Basal secretion of amylase, trypsinogen, and chymotrypsinogen from isolated dispersed pancreatic acini of acetaldehyde-treated rats was increased by 40-50%. Nicotine (5-25 mM) induced a profound increase in secretion of the same enzymes from isolated acini of both saline- and acetaldehyde-treated rats, but in the latter group there was a concomitant rise in LDH release. Furthermore, CCK-8 (1 nM), secretin (1 microM), and carbachol (10 microM) either alone or in combination with nicotine (12.5 mM) produced a profound stimulation in amylase, trypsinogen, and chymotrypsinogen secretion from acini of both groups of rats. On the other hand, secretion of 3H-pulse-labeled proteins from isolated acini of acetaldehyde-treated rats by nicotine was decreased by approximately 50% compared with the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde inhibition of protein synthesis in isolated rat pancreatic acini.

Exposure of isolated dispersed pancreatic acini to increasing concentrations of ethanol (5 to 500 mM) or acetaldehyde (0.5 to 100 mM) produced a progressive inhibition of [3H]leucine incorporation into both "cellular" (those remaining in the cell) and "secretory" (those released into the medium) proteins. Whereas 500 mM ethanol caused 90-95% inhibition in the synthesis of "cellular" and "secretory" proteins, the concentration of acetaldehyde needed to produce a similar inhibition was found to be 50 mM. All subsequent experiments were performed with 12.5 mM acetaldehyde, a concentration that consistently inhibited acinar protein synthesis by about 50%. The acetaldehyde-mediated inhibition of acinar protein synthesis was partially normalized when this metabolite was removed after 30 min during a 90-min incubation period. In the presence of acetaldehyde, the secretion of 3H-pulse-labeled proteins, but not amylase, trypsinogen, or chymotrypsinogen, was greatly depressed. Acetaldehyde also caused a marked reduction in [3H]uridine incorporation into acinar RNA. The entry of [3H]uridine, [3H]leucine, and [3H]aminoisobutyric acid into isolated acini was found to be slightly (15-25%) decreased by acetaldehyde. It is concluded that acetaldehyde exerts a direct toxic effect on isolated dispersed pancreatic acini as evidenced by diminution of both protein and RNA synthesis and decreased secretion of the newly synthesized proteins. This inhibitory effect of acetaldehyde could be partially reversed.

Biochemical changes in the pancreas of rats with chronic renal failure.

Chronic renal failure (CRF) was produced in female Sprague-Dawley rats by 7/8 nephrectomy. Creatinine clearance was depressed significantly (P less than 0.005) and blood urea nitrogen (BUN) increased in CRF rats when compared with the sham-operated (S) controls. CRF caused no apparent change in body weight but significantly increased pancreatic weight as well as increased DNA, RNA, and protein content. Pancreatic protein-to-DNA and RNA-to-DNA ratios were also found to be significantly higher in CRF rats than in the S controls. Trypsin-like activity and immunoreactive cationic trypsinogen levels were both increased in the pancreas of CRF rats, but not in their serum. On the other hand, protease inhibitory activity in the pancreas and serum was significantly decreased by CRF. The ability of the dispersed pancreatic acini isolated from CRF rats to incorporate [3H]-leucine into protein, in the absence and presence of 0.25 nM cholecystokinin octapeptide (CCK-8), was found to be lower than in the controls. Furthermore, discharge of both trypsinogen and chymotrypsinogen induced by CCK-8 was markedly reduced from acini of CRF rats as compared with the S controls. In contrast, lactate dehydrogenase (LDH) was released more readily from pancreatic acini of CRF. It is concluded that mild CRF produces hyperplasia and hypertrophy of the pancreas and lowers the responsiveness of acini to CCK-8 with respect to synthesis and secretion of proteins.

Irreversible inhibition by acetaldehyde of cholecystokinin-induced amylase secretion from isolated rat pancreatic acini.

Acetaldehyde inhibited both amylase secretion induced by maximal concentrations (300 pM) of cholecystokinin octapeptide and the binding of radioiodinated cholecystokinin to receptors on isolated rat pancreatic acini. This inhibition was concentration dependent (10 mM to 1 M for amylase secretion and 100 mM to 1 M for binding). However, a correlation between the two inhibitory effects could not be obtained. Furthermore, the inhibitory effects were not reversible. Acetaldehyde did not alter the basal amylase secretion between 6 and 45 mM concentrations. However, 60, 100 and 300 mM acetaldehyde significantly decreased basal amylase secretion; no significant change in amylase secretion was observed at 600 mM and 1 M. Higher concentrations of acetaldehyde produced a 2- to 10-fold increase in basal amylase secretion. 51Cr release from prelabeled acini revealed no significant cell membrane damage between 10 and 600 mM acetaldehyde. These data suggest that acetaldehyde inhibition of cholecystokinin-induced amylase secretion is intracellularly mediated.

Acute pancreatitis.

The exocrine pancreas secretes into the gut on demand more than 20 proteins that are indispensable for digestion. In-vivo autodigestion is prevented by an array of natural safeguards. In acute pancreatitis, inappropriate intrapancreatic activation and release of pancreatic hydrolases occur, but the pathogenetic mechanism of autodigestion is unclear. The release of proteases, lipase and colipase, phospholipase A, vasoactive peptides, and other agents probably accounts for the edema, tissue destruction, fat necrosis, metabolic abnormalities, and complications. Ethyl alcohol abuse, gallstones, trauma, and other common and rare conditions can induce pancreatitis. The patient's outcome can be predicted by certain prognostic signs. Ultrasonography and computerized tomography are invaluable diagnostic tools and magnetic resonance imaging appears promising. Hemodynamic monitoring, intensive care with colloid and crystalloid infusions, correction of electrolyte abnormalities, judicious use of antibiotics, peritoneal lavage, drainage of pancreatic exudation fluids, and surgical intervention require a team approach, especially in patients with multiple complications. Additional research is needed into the pathogenetic mechanism of autodigestion and the design of specific therapies.

Nonparallel discharge of digestive enzymes from isolated pancreatic acini.

The secretion of amylase, trypsinogen, chymotrypsinogen and proelastase from isolated rat dispersed pancreatic acini was investigated in the absence (basal) and presence of two concentrations of CCK8 (50 and 500 pM), carbachol (2.5 and 7.5 microM) and secretin (10 nM and 1 microM). The unstimulated (basal) rate of release of each of the digestive enzymes was essentially the same. However, whereas both doses of CCK8 and carbachol caused a preferential release of chymotrypsinogen over that of amylase and trypsinogen, the magnitude of stimulated release of amylase, trypsinogen and chymotrypsinogen by 1 microM secretin was found to be similar for each of the enzymes. Furthermore, none of the secretagogues caused a significant enhancement in proelastase release. The present data demonstrate that whereas CCK8 and carbachol induce a greater release of chymotrypsinogen over that of amylase or trypsinogen, release of all three enzymes was equally stimulated by secretin from isolated pancreatic acini.