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Histamine does not mediate mucosal permeability changes after subclinical intestinal ischemia-reperfusion injury
Histamine Does Not Mediate After Subclinical Intestinal ByJacob
Mucosal Permeability Ischemia-Reperfusion
Changes Injury
C. Langer, Sarvjit S. Sohal, and Jean Marshall Hamilton, Ontario
0 Subclinical intestinal ischemia-repetfusion injury (IRI) increases mucosal permeability, and may be an important mechanism in the etiology of necrotizing enterocolitis. The current study was designed to assess the role of histamine in mediating this phenomenon. Six-week-old rats underwent lo-minute superior mesenteric artery occlusion (SMAO) or sham operation, and ileal mucosal permeability to %r EDTA was measured 30 minutes after reperfusion. Rats were pretreated with intravenous saline, mepyramine (6 mg/ kg), or ranitidine (5 mg/kg). SMAO resulted in a significant increase in permeability compared to sham, which was not attenuated by either of the histamine antagonists. In a second experiment, mucosal permeability to 51Cr EDTA was measured in B-week-old rats during aortic infusion of saline or histamine (0.5 mg/kg/min). There was no significant increase in permeability as a result of histamine infusion. In a third experiment, 6-week-old and lo-day-old rats underwent sham or lo-minute SMAO, and both portal vein and ileal tissue histamine levels were measured 30 minutes after reperfusion. There was no significant difference between sham and SMAO with respect to portal vein histamine or tissue histamine at either age. In conclusion: (1) increased permeability was not blocked by either HI or Hz blockers; (2) histamine infusion did not increase permeability; and (3) SMAO did not increase portal vein or tissue histamine levels. These data suggest that histamine does not play a role in mediating the increase in permeability after subclinical IRI in this model. Copyright hl 1993 by W.B. Saunders Company INDEX WORDS: Necrotizing enterocolitis, mucosal permeability, histamine.
T
HE ETIOLOGY of neonatal necrotizing enterocolitis (NEC) is unknown, although intestinal ischemia, intraluminal substrate, and bacteria have all been implicated. ’ Several unified theories have been proposed which take into account the multifactorial nature of this disease.” We have previously suggested that a subclinical insult to the gut may cause an increase in mucosal permeability to bacteria and toxic intraluminal proteins. The presence of these factors within the bowel wall may then result in the inflammation characteristic of NEC. To investigate this possibility, we have used a weanling rat model to show that subclinical intestinal ischemiareperfusion injury (IRI) results in an increase in mucosal permeability to 51Cr EDTA.3 These changes are reversible after several hours, and appear to be mediated by local tissue factors.? Current studies are designed to investigate the mechanism by which this increase in permeability occurs. In this article we report the results of experiJournalofPediatric Surgery, Vol 28, No 9 (September),
1993:
pp 1113-l 116
ments examining the role of histamine as a putative mediator. Three approaches were taken: (1) specific blockade of IRI-induced permeability changes with histamine receptor antagonists; (2) reproduction of the permeability changes by infusion of histamine; and (3) measurement of tissue and portal vein histamine levels immediately after IRI. MATERIALS AND METHODS
Animals Weanling male Sprague-Dawley rats aged 6 weeks ( 1.50 to 180 g) were housed under standard conditions, fed Purina rat chow. and given only water for 12 hours prior to all experiments. Ten-day-old Sprague-Dawley rats were housed with their mother, and separated approximately 1 hour prior to experimentation. All studies were approved by the MeMaster University Committee on Animal Experimentation.
Superior Mesenteric Artery Occlusion Details of this technique have been previously described.” The technique was similar for weanling and lo-day-old rats. Anesthesia was induced using intraperitoneal pentobarbital (45 mg/kg). A midline laparotomy was made, the small intestine was reflected to the left, and the superior mesenteric artery was exposed. The artery was occluded with a microaneurysm clip, taking care not to occlude the superior mesenteric vein. To ensure adequate occlusion, the bowel was examined for pallor and absence of pulsation in the mesenteric vessels. Upon reperfusion, the bowel was noted to become pink, and return of mesenteric pulsation was seen. Anesthesia was maintained by periodic intraperitoneal administration of pentobarbital (5 to 10 mgikg). Sham operation involved the same technique and exposure, without clipping of the superior mesenteric artery.
Histamine Infusion Weanling rats were anesthetized as above, and a carotid artery catheter was placed and positioned with its tip in the aorta. This technique was developed and catheter position validated in a series of rat.5 prior to performing the infusion experiments. Histamine was infused at a rate of 2 mL/h. delivering a dose of 5 mg/kg/min. Control animals received the same volume of saline without
From the Intestinal Disease Research Unit and the Deparrments of Sutge~ and Pathology, McMaster University, Hamilton, Ontario. Presented at the 24th Annual Meeting of the Canudian Association of Paediattic Surgeons, Ottawa, Ontario. September 10-13, 1992. Supported in part by Medical Research Council of’ Canada Grant Mx10878. Address reprint requests to Jacob C. Lunger, MD, Division of Pediatric Sutgetyy, St Louis Children? Hospital. Km 5WI2. 400 S Kingshighway, St Loais, MO 631 IO. Copyright c 1993 by W B. Saunder.s Cornpar!) 0022.3468193/2809-0009$03.0010 1113
1114
LANGER, SOHAL, AND MARSHALL
histamine. Prior to beginning the infusion, an isolated ileal loop was prepared as described below.
8
Measurement of Mucosal Permeability A technique modified from Ramage et al was used.6 The ileum was ligated 20 cm from the cecum and at the ileocecal junction, taking care not to interfere with the blood supply to the isolated segment. At the time of intestinal reperfusion, or at the beginning of histamine infusion, 1.0 mL of 51Cr EDTA solution (0.065 mCi/mL in distilled water, McMaster Pharmacy Department) was injected into the ileal segment. Blood was sampled (0.5 mL per sample) 30 minutes after reperfusion or 30 minutes after beginning the histamine infusion. Samples were counted using a 1282 Compugamma counter (LKB-Wallac Corporation, Turku, Finland). Results were expressed as the number of counts per sample/number of counts in a IO-ILLstandard of 51Cr EDTA used in that day’s experiment (std).
Histamine Blocker Experiments The effects of the Hr blocker mepyramine and the Hz blocker ranitidine on IRI-induced mucosal permeability were assessed in viva. Weanling rats were pretreated with mepyramine (6 mg/kg) or ranitidine (5 mg/kg) given by intraperitoneal injection 45 minutes prior to the experiment. Rats then underwent sham procedure or lo-minute superior mesenteric artery occlusion @MAO), followed by assessment of mucosal permeability as described above.
Measurement of Tissue and Serum Histamine Levels Tissue and portal vein histamine levels were assessed in both weanling rats and lo-day-old rats after either SMAO or sham procedure. Thirty minutes after reperfusion, blood was obtained from the portal vein, a segment of terminal ileum was excised, and the animal was sacrificed. Serum levels of histamine and histamine concentrations in homogenized tissue samples were measured by a radioenzyme histamine assay technique as described by Shaff and Beaven.’ Control and test samples were examined in parallel and values assessed relative to a standard curve.
Serum
s
Cr WTA 4
l
2
,
Meansham
q
MeanSMAO
pxO.OSvssham
0 Ranltidine
Fig 1. Results of histamine blockers on IRI-induced mucosal permeability changes. Five animals were studied in each group. There was a significant increase in permeability 30 minutes after reperfusion in animals undergoing SMAO, with 57Cr EDTA levels approximately lo-fold those in the sham animals. This increase in permeability was not attenuated by either of the histamine receptor antagonists.
30 minutes of infusion). Infusion of histamine at higher doses resulted in a very high mortality rate. Histamine Levels
Tissue levels of histamine are shown in Fig 2. There was no significant difference between animals under-
A
4000
1
Hlstamlne content (ng/mg tissue)
Data Analysis
Sham
SMAO
Sham
SMAO
Data from each experimental group were compared with the corresponding sham group using an unpaired Student’s t test. A P value of 0.05 was considered statistically significant. RESULTS
Histamine Blockers
Results of these studies are shown in Fig 1. Five animals were studied in each group. There was a significant increase in permeability 30 minutes after reperfusion in animals undergoing SMAO, with Wr EDTA levels approximately lo-fold those in the sham animals. This increase in permeability was not attenuated by either of the histamine receptor antagonists.
B
30
1
Histamine content (ngimg tissue)
Histamine Infusion Six animals were studied in each group. There was no significant increase in mucosal permeability as a result of histamine infusion (0.5 mg/kg/min) compared with infusion of normal saline (serum Wr EDTA of 2.02 i 1.4 v 1.63 2 0.5 counts/mL/std after
Fig 2. Tissue levels of histamine in (A) weanling and (B) IO-day-old rats. There was no significant difference between animals undergoing lo-minute SMAO and those undergoing sham operation.
HISTAMINE
AND MUCOSAL
1115
PERMEABILITY
going lo-minute SMAO and those undergoing sham operation. This was true of both weanling and IO-dayold rats. Portal vein histamine levels are shown in Fig 3. There was again no significant difference between animals undergoing ten-minute SMAO and those undergoing sham operation, both in weanling and in lo-day-old rats. DISCUSSION
Most histamine in the intestinal tract is present in mast cells, although other histamine-containing cells have been described.8 Histamine stimulates gastric acid secretion9 increases smooth muscle contractility?N’and affects intestinal blood flow.i1~12Histamine is also an important component of the inflammatory response, from both allergic and other stimuli. The well-known role of histamine early in the process of inflammation made it a primary candidate as the
A
40-
Histamine content WmU
Sham
6
SMAO
41
mediator of mucosal permeability changes seen in this model of intestinal IRI. Histamine has been shown to produce a number of effects in the intestine which are similar to those produced by intestinal injury. Jacobson et al initially showed that histamine reproduced some of the systemic effects of endotoxic shock in a canine model,i” and subsequently demonstrated increases in oxygen consumption, intestinal blood flow,14 and motility.15 Histamine has also been shown to increase intestinal capillary permeability.16 The evidence for histamine release after IRI is less clear. In the heart, histamine is released during the reperfusion phase after coronary artery occlusion, and can be measured in the serum after myocardial infarction in dogs. l7 However, histamine does not seem to contribute to the reactive hyperemia seen after IRI in skeletal muscle,i8 a tissue in which few mast cells are found. Kusche et al measured serum histamine after intestinal IRI, and correlated the increase in plasma histamine with a decrease in intestinal diamine oxidase activity.“~?” This phenomenon occurred in a number of species.” The administration of aminoguanidine (a diamine oxidase inhibitor which prevents the breakdown of histamine by diamine oxidase) resulted in a higher mortality, and this effect could be blocked by administration of histamine antagonists.?” These data support a role for histamine in the systemic effects seen following intestinal IRI. On the other hand, Granger et al, in a feline model, were unable to demonstrate any involvement of histamine in capillary permeability changes after intestinal IRI.‘? There is evidence that histamine, rather than being the primary mediator, may play a promoting or supportive role in the events following IRI. A number of authors have demonstrated that histamine release may be initiated by free radicals.?“.‘” Similarly, early increases in serum histamine levels, before or concurrent with changes in the xanthine oxidase system, have been seen in both skeletal muscle and intestinal IRI.2526
Histamine content @s/ml)
Sham
SMAO
Fig 3. Portal vein histamine levels in (A) weanling and (B) W-dayold rats. There was no significant difference between animals undergoing Xl-minute SMAO and those undergoing sham operation.
In the present study, we were unable to identify an increase in serum or tissue histamine, were unable to reproduce the permeability changes by infusing histamine, and were unable to block the increase in permeability with histamine antagonists, strongly suggesting that histamine is not involved in this phenomenon. Other putative mediators, including oxygen free radicals, eicosanoids, or preformed cytokines such as tumor necrosis factor-a, must be investigated further.
1116
LANGER, SOHAL, AND MARSHALL
REFERENCES 1. Kliegman RM: Models of the pathogenesis of necrotizing enterocolitis. J Pediatr 117:S2-S5, 1990 (suppl) 2. Kosloske AM: A unifying hypothesis for pathogenesis and prevention of necrotizing enterocolitis. J Pediatr 117:S68-74, 1990 (suppl) 3. Langer JC, Sohal SS, Riddell RH: Mild intestinal ischemiareperfusion injury causes an early, transient increase in mucosal permeability in the rat. J Pediatr Surg 26:502, 1991 (abstr) 4. Langer JC, Sohal SS: Increased mucosal permeability after ischemia-reperfusion injury is mediated by local tissue factors. J Pediatr Surg 27:329-332, 1992 5. Langer JC, Sohal SS, Riddell RR: Mucosal permeability to “‘Cr EDTA following subclinical intestinal ischemia-reperfusion injury in the weanling rat. J Pediatr Surg 28601605, 1993 6. Ramage JK, Stanisz A. Scicchitano R, et al: Effect of immunological reactions on rat intestinal epithelium. Correlation of increased gut permeability to 5’Cr EDTA and ovalbumin during inflammation and anaphylaxis in the rat. Gastroenterology 94:13681375,198s 7. Shaff RE, Beaven MN: Increased sensitivity of the enzymatic isotopic assay of histamine: Measurement of histamine in plasma and serum. Anal Biochem 94:425-430,1979 8. Metcalfe DD: Mast cell mediators with emphasis on intestinal mast cells. Allergy 53:563-575, 1984 9. Chew CS, Hersey SJ, Sachs G, et al: Histamine responsiveness of isolated gastric glands. Am J Physiol238:G312-320,198O 10. Langer JC, Mulvihill SJ, Harrison MR, et al: Ontogeny of the smooth muscle response to histamine in rabbit and human small bowel. J Dev Physiol12:169-172.1989 11. Schwaiger M, Fondacaro JD, Jacobson ED: Effects of glucagon, histamine, and perhexiline on the ischemic canine mesenteric circulation. Gastroenterology 77:730-735, 1979 12. Walus KM, Fondacaro JD, Jacobson ED: Mesenteric vascular reactivity to histamine receptor agonists and antagonists. Dig Dis Sci 26:438-443. 1981 13. Jacobson ED, Mehlman B, Kalas JP: Vasoactive mediators as the “trigger mechanism” of endotoxic shock. J Clin Invest 43:1000-1013, 1964 14. Pawlik W, Shepherd AP, Jacobson ED: Effects of vasoactive
agents on intestinal oxygen consumption and blood flow in dogs. J Clin Invest 56:484-490, 1975 15. Shehadeh Z. Price WE, Jacobson ED: Effects of vasoactive agents on intestinal blood flow and motility in the dog. Am J Physiol216:386-392. 1969 16. Mortillaro NA, Granger DN, Kvietys PR, et al: Effects of histamine and histamine antagonists on intestinal capillary permeability. Am J Physiol240:G381-386, 1981 17. Masini E, Giannella E, Bianchi S. et al: Histamine release in acute coronary occlusion-reperfusion in isolated guinea-pig heart. Agents Actions 23:266-269,198s 18. Daniel A, Honig CR: Does histamine influence vasodilation caused by prolonged arterial occlusion or heavy exercise? J Pharmacol Exp Ther 215:533-538,198O 19. Kusche J. Stahlknecht C-D. Lorenz W, et al: Diamine oxidase activity and histamine release in dogs following acute mesenteric artery occlusion. Agents Actions 7:81-84. 1977 20. Kusche J, Lorenz W. Stahlknecht C, et al: Intestinal diamine oxidase and histamine release in rabbit mesenteric ischemia. Gastroenterology 80:980-987. 1981 21. Kusche J, Stahlknecht C-D, Lorenz W, et al: Comparison of alterations in the histamine-diamine oxidase system during acute intestinal ischaemia in pigs, dogs, and rabbits: Evidence for a uniform pathophysiological mechanism? Agents Actions 9:49-52, 1979 22. Granger DN, Rutili G. McCord JM: Superoxide radicals in feline intestinal ischemia. Gastroenterology 81:22-29, 1981 23. Mannaioni PF, Masini E: The release of histamine by free radicals. Free Rad Biol Med 5:177-197. 1988 24. Boros M, Kaszaki J. Nagy S: Oxygen free radical-induced histamine release during intestinal ischemia and reperfusion. Eur Surg Res 21:297-304, 1989 25. Fried1 HP, Smith DJ, Thomson PD, et al: Histamine and xanthine oxidase activity in a human model of ischemia-reperfusion injury, Surg Forum 40:587-589, 1989 26. Caty MG, Schmeling DJ, Fried1 HP. et al: Histamine: A promoter of xanthine oxidase activity in intestinal ischemiai reperfusion. J Pediatr Surg 25:218-223, 1990
Mucosal Permeability Ischemia-Reperfusion
Changes Injury
C. Langer, Sarvjit S. Sohal, and Jean Marshall Hamilton, Ontario
0 Subclinical intestinal ischemia-repetfusion injury (IRI) increases mucosal permeability, and may be an important mechanism in the etiology of necrotizing enterocolitis. The current study was designed to assess the role of histamine in mediating this phenomenon. Six-week-old rats underwent lo-minute superior mesenteric artery occlusion (SMAO) or sham operation, and ileal mucosal permeability to %r EDTA was measured 30 minutes after reperfusion. Rats were pretreated with intravenous saline, mepyramine (6 mg/ kg), or ranitidine (5 mg/kg). SMAO resulted in a significant increase in permeability compared to sham, which was not attenuated by either of the histamine antagonists. In a second experiment, mucosal permeability to 51Cr EDTA was measured in B-week-old rats during aortic infusion of saline or histamine (0.5 mg/kg/min). There was no significant increase in permeability as a result of histamine infusion. In a third experiment, 6-week-old and lo-day-old rats underwent sham or lo-minute SMAO, and both portal vein and ileal tissue histamine levels were measured 30 minutes after reperfusion. There was no significant difference between sham and SMAO with respect to portal vein histamine or tissue histamine at either age. In conclusion: (1) increased permeability was not blocked by either HI or Hz blockers; (2) histamine infusion did not increase permeability; and (3) SMAO did not increase portal vein or tissue histamine levels. These data suggest that histamine does not play a role in mediating the increase in permeability after subclinical IRI in this model. Copyright hl 1993 by W.B. Saunders Company INDEX WORDS: Necrotizing enterocolitis, mucosal permeability, histamine.
T
HE ETIOLOGY of neonatal necrotizing enterocolitis (NEC) is unknown, although intestinal ischemia, intraluminal substrate, and bacteria have all been implicated. ’ Several unified theories have been proposed which take into account the multifactorial nature of this disease.” We have previously suggested that a subclinical insult to the gut may cause an increase in mucosal permeability to bacteria and toxic intraluminal proteins. The presence of these factors within the bowel wall may then result in the inflammation characteristic of NEC. To investigate this possibility, we have used a weanling rat model to show that subclinical intestinal ischemiareperfusion injury (IRI) results in an increase in mucosal permeability to 51Cr EDTA.3 These changes are reversible after several hours, and appear to be mediated by local tissue factors.? Current studies are designed to investigate the mechanism by which this increase in permeability occurs. In this article we report the results of experiJournalofPediatric Surgery, Vol 28, No 9 (September),
1993:
pp 1113-l 116
ments examining the role of histamine as a putative mediator. Three approaches were taken: (1) specific blockade of IRI-induced permeability changes with histamine receptor antagonists; (2) reproduction of the permeability changes by infusion of histamine; and (3) measurement of tissue and portal vein histamine levels immediately after IRI. MATERIALS AND METHODS
Animals Weanling male Sprague-Dawley rats aged 6 weeks ( 1.50 to 180 g) were housed under standard conditions, fed Purina rat chow. and given only water for 12 hours prior to all experiments. Ten-day-old Sprague-Dawley rats were housed with their mother, and separated approximately 1 hour prior to experimentation. All studies were approved by the MeMaster University Committee on Animal Experimentation.
Superior Mesenteric Artery Occlusion Details of this technique have been previously described.” The technique was similar for weanling and lo-day-old rats. Anesthesia was induced using intraperitoneal pentobarbital (45 mg/kg). A midline laparotomy was made, the small intestine was reflected to the left, and the superior mesenteric artery was exposed. The artery was occluded with a microaneurysm clip, taking care not to occlude the superior mesenteric vein. To ensure adequate occlusion, the bowel was examined for pallor and absence of pulsation in the mesenteric vessels. Upon reperfusion, the bowel was noted to become pink, and return of mesenteric pulsation was seen. Anesthesia was maintained by periodic intraperitoneal administration of pentobarbital (5 to 10 mgikg). Sham operation involved the same technique and exposure, without clipping of the superior mesenteric artery.
Histamine Infusion Weanling rats were anesthetized as above, and a carotid artery catheter was placed and positioned with its tip in the aorta. This technique was developed and catheter position validated in a series of rat.5 prior to performing the infusion experiments. Histamine was infused at a rate of 2 mL/h. delivering a dose of 5 mg/kg/min. Control animals received the same volume of saline without
From the Intestinal Disease Research Unit and the Deparrments of Sutge~ and Pathology, McMaster University, Hamilton, Ontario. Presented at the 24th Annual Meeting of the Canudian Association of Paediattic Surgeons, Ottawa, Ontario. September 10-13, 1992. Supported in part by Medical Research Council of’ Canada Grant Mx10878. Address reprint requests to Jacob C. Lunger, MD, Division of Pediatric Sutgetyy, St Louis Children? Hospital. Km 5WI2. 400 S Kingshighway, St Loais, MO 631 IO. Copyright c 1993 by W B. Saunder.s Cornpar!) 0022.3468193/2809-0009$03.0010 1113
1114
LANGER, SOHAL, AND MARSHALL
histamine. Prior to beginning the infusion, an isolated ileal loop was prepared as described below.
8
Measurement of Mucosal Permeability A technique modified from Ramage et al was used.6 The ileum was ligated 20 cm from the cecum and at the ileocecal junction, taking care not to interfere with the blood supply to the isolated segment. At the time of intestinal reperfusion, or at the beginning of histamine infusion, 1.0 mL of 51Cr EDTA solution (0.065 mCi/mL in distilled water, McMaster Pharmacy Department) was injected into the ileal segment. Blood was sampled (0.5 mL per sample) 30 minutes after reperfusion or 30 minutes after beginning the histamine infusion. Samples were counted using a 1282 Compugamma counter (LKB-Wallac Corporation, Turku, Finland). Results were expressed as the number of counts per sample/number of counts in a IO-ILLstandard of 51Cr EDTA used in that day’s experiment (std).
Histamine Blocker Experiments The effects of the Hr blocker mepyramine and the Hz blocker ranitidine on IRI-induced mucosal permeability were assessed in viva. Weanling rats were pretreated with mepyramine (6 mg/kg) or ranitidine (5 mg/kg) given by intraperitoneal injection 45 minutes prior to the experiment. Rats then underwent sham procedure or lo-minute superior mesenteric artery occlusion @MAO), followed by assessment of mucosal permeability as described above.
Measurement of Tissue and Serum Histamine Levels Tissue and portal vein histamine levels were assessed in both weanling rats and lo-day-old rats after either SMAO or sham procedure. Thirty minutes after reperfusion, blood was obtained from the portal vein, a segment of terminal ileum was excised, and the animal was sacrificed. Serum levels of histamine and histamine concentrations in homogenized tissue samples were measured by a radioenzyme histamine assay technique as described by Shaff and Beaven.’ Control and test samples were examined in parallel and values assessed relative to a standard curve.
Serum
s
Cr WTA 4
l
2
,
Meansham
q
MeanSMAO
pxO.OSvssham
0 Ranltidine
Fig 1. Results of histamine blockers on IRI-induced mucosal permeability changes. Five animals were studied in each group. There was a significant increase in permeability 30 minutes after reperfusion in animals undergoing SMAO, with 57Cr EDTA levels approximately lo-fold those in the sham animals. This increase in permeability was not attenuated by either of the histamine receptor antagonists.
30 minutes of infusion). Infusion of histamine at higher doses resulted in a very high mortality rate. Histamine Levels
Tissue levels of histamine are shown in Fig 2. There was no significant difference between animals under-
A
4000
1
Hlstamlne content (ng/mg tissue)
Data Analysis
Sham
SMAO
Sham
SMAO
Data from each experimental group were compared with the corresponding sham group using an unpaired Student’s t test. A P value of 0.05 was considered statistically significant. RESULTS
Histamine Blockers
Results of these studies are shown in Fig 1. Five animals were studied in each group. There was a significant increase in permeability 30 minutes after reperfusion in animals undergoing SMAO, with Wr EDTA levels approximately lo-fold those in the sham animals. This increase in permeability was not attenuated by either of the histamine receptor antagonists.
B
30
1
Histamine content (ngimg tissue)
Histamine Infusion Six animals were studied in each group. There was no significant increase in mucosal permeability as a result of histamine infusion (0.5 mg/kg/min) compared with infusion of normal saline (serum Wr EDTA of 2.02 i 1.4 v 1.63 2 0.5 counts/mL/std after
Fig 2. Tissue levels of histamine in (A) weanling and (B) IO-day-old rats. There was no significant difference between animals undergoing lo-minute SMAO and those undergoing sham operation.
HISTAMINE
AND MUCOSAL
1115
PERMEABILITY
going lo-minute SMAO and those undergoing sham operation. This was true of both weanling and IO-dayold rats. Portal vein histamine levels are shown in Fig 3. There was again no significant difference between animals undergoing ten-minute SMAO and those undergoing sham operation, both in weanling and in lo-day-old rats. DISCUSSION
Most histamine in the intestinal tract is present in mast cells, although other histamine-containing cells have been described.8 Histamine stimulates gastric acid secretion9 increases smooth muscle contractility?N’and affects intestinal blood flow.i1~12Histamine is also an important component of the inflammatory response, from both allergic and other stimuli. The well-known role of histamine early in the process of inflammation made it a primary candidate as the
A
40-
Histamine content WmU
Sham
6
SMAO
41
mediator of mucosal permeability changes seen in this model of intestinal IRI. Histamine has been shown to produce a number of effects in the intestine which are similar to those produced by intestinal injury. Jacobson et al initially showed that histamine reproduced some of the systemic effects of endotoxic shock in a canine model,i” and subsequently demonstrated increases in oxygen consumption, intestinal blood flow,14 and motility.15 Histamine has also been shown to increase intestinal capillary permeability.16 The evidence for histamine release after IRI is less clear. In the heart, histamine is released during the reperfusion phase after coronary artery occlusion, and can be measured in the serum after myocardial infarction in dogs. l7 However, histamine does not seem to contribute to the reactive hyperemia seen after IRI in skeletal muscle,i8 a tissue in which few mast cells are found. Kusche et al measured serum histamine after intestinal IRI, and correlated the increase in plasma histamine with a decrease in intestinal diamine oxidase activity.“~?” This phenomenon occurred in a number of species.” The administration of aminoguanidine (a diamine oxidase inhibitor which prevents the breakdown of histamine by diamine oxidase) resulted in a higher mortality, and this effect could be blocked by administration of histamine antagonists.?” These data support a role for histamine in the systemic effects seen following intestinal IRI. On the other hand, Granger et al, in a feline model, were unable to demonstrate any involvement of histamine in capillary permeability changes after intestinal IRI.‘? There is evidence that histamine, rather than being the primary mediator, may play a promoting or supportive role in the events following IRI. A number of authors have demonstrated that histamine release may be initiated by free radicals.?“.‘” Similarly, early increases in serum histamine levels, before or concurrent with changes in the xanthine oxidase system, have been seen in both skeletal muscle and intestinal IRI.2526
Histamine content @s/ml)
Sham
SMAO
Fig 3. Portal vein histamine levels in (A) weanling and (B) W-dayold rats. There was no significant difference between animals undergoing Xl-minute SMAO and those undergoing sham operation.
In the present study, we were unable to identify an increase in serum or tissue histamine, were unable to reproduce the permeability changes by infusing histamine, and were unable to block the increase in permeability with histamine antagonists, strongly suggesting that histamine is not involved in this phenomenon. Other putative mediators, including oxygen free radicals, eicosanoids, or preformed cytokines such as tumor necrosis factor-a, must be investigated further.
1116
LANGER, SOHAL, AND MARSHALL
REFERENCES 1. Kliegman RM: Models of the pathogenesis of necrotizing enterocolitis. J Pediatr 117:S2-S5, 1990 (suppl) 2. Kosloske AM: A unifying hypothesis for pathogenesis and prevention of necrotizing enterocolitis. J Pediatr 117:S68-74, 1990 (suppl) 3. Langer JC, Sohal SS, Riddell RH: Mild intestinal ischemiareperfusion injury causes an early, transient increase in mucosal permeability in the rat. J Pediatr Surg 26:502, 1991 (abstr) 4. Langer JC, Sohal SS: Increased mucosal permeability after ischemia-reperfusion injury is mediated by local tissue factors. J Pediatr Surg 27:329-332, 1992 5. Langer JC, Sohal SS, Riddell RR: Mucosal permeability to “‘Cr EDTA following subclinical intestinal ischemia-reperfusion injury in the weanling rat. J Pediatr Surg 28601605, 1993 6. Ramage JK, Stanisz A. Scicchitano R, et al: Effect of immunological reactions on rat intestinal epithelium. Correlation of increased gut permeability to 5’Cr EDTA and ovalbumin during inflammation and anaphylaxis in the rat. Gastroenterology 94:13681375,198s 7. Shaff RE, Beaven MN: Increased sensitivity of the enzymatic isotopic assay of histamine: Measurement of histamine in plasma and serum. Anal Biochem 94:425-430,1979 8. Metcalfe DD: Mast cell mediators with emphasis on intestinal mast cells. Allergy 53:563-575, 1984 9. Chew CS, Hersey SJ, Sachs G, et al: Histamine responsiveness of isolated gastric glands. Am J Physiol238:G312-320,198O 10. Langer JC, Mulvihill SJ, Harrison MR, et al: Ontogeny of the smooth muscle response to histamine in rabbit and human small bowel. J Dev Physiol12:169-172.1989 11. Schwaiger M, Fondacaro JD, Jacobson ED: Effects of glucagon, histamine, and perhexiline on the ischemic canine mesenteric circulation. Gastroenterology 77:730-735, 1979 12. Walus KM, Fondacaro JD, Jacobson ED: Mesenteric vascular reactivity to histamine receptor agonists and antagonists. Dig Dis Sci 26:438-443. 1981 13. Jacobson ED, Mehlman B, Kalas JP: Vasoactive mediators as the “trigger mechanism” of endotoxic shock. J Clin Invest 43:1000-1013, 1964 14. Pawlik W, Shepherd AP, Jacobson ED: Effects of vasoactive
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