Michael A. Dubick

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.

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.

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 β-glucuronidase was significantly higher in ascites compared to serum in all groups. On the other hand, levels of immunoreactive α1-protease inhibitor and α2-macroglobulin in ascites fluid were about half the average concentrations reported for normal serum. Significant amounts of tryptic amidase activity (61.7±13.7 μg/ml) were observed, indicating a trypsin-α2-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.

Hypertension Induced Alterations in Copper and Zinc Metabolism: A Link to Vascular Disease?

Ischemic heart disease is the leading cause of death in the United States and other industrialized countries. Although the etiology of disease is without question multifactorial in nature, several potential risk factors have been agreed upon. These risk factors include hypercholesterolemia, hypertension, electrocardiogram abnormalities, cigarette smoking and diabetes.1 During the last decade it has been proposed that Cu deficiency may also be a significant risk factor for vascular disease. This hypothesis has been based on the observations that severe Cu deficiency in experimental and domestic animals can result in connective tissue defects producing myocardial damage and aortic aneurysms, and that the dietary intake of Cu is often below that suggested by health agencies.2,3 Furthermore, the risk of Cu deficiency is thought to be increased by the consumption of excess Zn in the diet, as these two elements can be biologically antagonistic.3–5

The effects of ozone on lung, heart, and liver superoxide dismutase and glutathione peroxidase activities in the protein-deficient rat

The effects of protein deficiency or food restriction and ozone exposure on lung, heart and liver superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were studied in weanling and adult rats. Two groups of rats were fed diets containing 4 or 16% protein. A third group was fed the 16% protein diet, but at the level consumed by the rats fed the 4% protein diet. After 3 weeks (weanling) or 5 weeks (adult), one-half of the rats in each group were exposed continuously to 0.64 ppm ozone for 7 days. In adult rat lung, O3 exposure typically stimulated Cu,Zn-SOD and GPx activities in all groups, but in weanling rats only GPx activity was elevated and only in rats fed the 16% protein diet. Liver Cu,Zn-SOD activity was also influenced by diet; in adult rats, liver Mn-SOD and GPx activities were often depressed following O3 exposure. Heart SOD and GPx, however, were not affected by ozone or diet. The pulmonary and hepatic effects due to diet and O3 further illustrate the importance of nutritional status when assessing the health effects of O3 exposure.

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.

Biochemical changes in the exocrine pancreas of rats fed caffeine

Abstract Coffee consumption has been associated with pancreatic disorders, but the mechanisms involved remain to be elucidated. This investigation examines the effects of caffeine consumption on the structure and function of the exocrine pancreas. Groups of rats, fed ad libitum commercial laboratory diet, were given drinking water which contained either caffeine (0.09 mg/ml) or nothing at all. The rats were allowed drink ad libitum and were killed 6 weeks later. Final body and pancreatic weights were not significantly different between the groups at the end of the experimental period. Although no ultrastructural effects of caffeine on the pancreas were observed, amylase and trypsinogen activity was 35% higher in pancreatic homogenates from caffeine-fed rats compared with controls. In addition, levels of immunoreactive cationic trypsin(ogen) were 41% higher than control levels in pancreases from the caffeine-fed rats. Also, the circulating levels of amylase and immunoreactive cationic trypsin(ogen) in serum were lower in the caffeine group compared with controls. When dispersed pancreatic acini isolated from the caffeine-fed rats were incubated in vitro with increasing concentrations of CCK-8 or nicotine, the rate of release of amylase, tripsinogen, and chymotrypsinogen was lower than in the control rats. This effect did not appear to be due to inhibition of protein synthesis, as determined by [3H]leucine incorporation into acinar protein. These data suggest that prolonged intake of caffeine at common dietary levels inhibits pancreatic enzyme secretion.

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.

Hypotensive Resuscitation of Casualties in the Far-Forward Combat Environment: Effects of Select Crystalloids and Colloids on Signal Transduction Mediators in a Swine Model of Severe Hemorrhage

Abstract : Hemorrhage remains a major cause of death on the battlefield in conventional warfare (Bellamy. 1984). Current dogma dictates that early, adequate fluid resuscitation is crucial to reduce the mortality and morbidity associated with hemorrhagic shock. Yet, despite much research in the field and years of resuscitating thousands of patients, the optimal fluid and resuscitation strategy for the treatment of hemorrhagic hypovolemia remains unknown. However, with future combat strategies focused around the Future Force Warrior, greater dispersal of troops and fighting in urban settings and on non-linear battlefields, the likelihood of longer evacuation times for combat casualties is anticipated. As a consequence of these conditions and the logistic limitations of weight and cube, fluid resuscitation research within the Armys Combat Casualty Care Research Program has focused to investigate limited- or small-volume fluid resuscitation strategies. including permissive hypotension, in far-forward areas for the treatment of severe hemorrhage. The ultimate goals are to improve battlefield survival and to reduce or prevent early and late deleterious sequelae in the injured soldier. For the military the concept of hypotensive resuscitation, or fluid resuscitation to a blood pressure below pre-hemorrhage levels. currently seems to be a rational approach to compensate for the limited amount of fluid available on the battlefield to treat casualties, and to minimize the chance for rebleeding from penetrating injuries. In addition. studies in experimental animals have suggested that hypotensive resuscitation may improve survival from an uncontrolled hemorrhage (Capone et al. 1995; Stern et al. 2001).