JOURNAL
OF SURGICAL
RESEARCH
48, 249-253 (1990)
Muramyl Dipeptide Improves Mononuclear Phagocyte System Function in Obstructive Jaundice CHARLES W. DUNN, M.D.,’ AND JURETA W. HORTON, PH.D. With the technical assistance of Paula B. Walker, B.S. Department
of Surgery, University
of Texas Southwestern
Submitted
for publication
Previous studies have demonstrated depression of the mononuclear phagocyte system (MPS) of which the liver comprises SO-85% in animals subjected to 2 1 days of obstructive jaundice. This study examined the ability of a macrophage stimulant, muramyl dipeptide (MDP), to reverse MPS dysfunction in an obstructive jaundice rat model. Sixty-two male Sprague-Dawley rats underwent sham (n = 29) laparotomy or common duct ligation (CDL) (n = 33) and were studied after 21 days. Animals were injected with l-3.5 X 10’ Escherichia coli via a lateral tail vein, and colony-forming units (CFU) of the liver, lung, and spleen were determined at two time intervals: 30 min postinjection to determine the phagocytic activity of MPS (sham, n = 16; CDL, n = 20) and 24 hr postinjection to determine cytotoxic activity of MPS (sham, n = 13; CDL, n = 13). MDP (3 pg/g) was administered subcutaneously 24 hr prior to E. coli injection in 6 sham and 10 CDL rats studied at the 30-min time interval and 7 sham and 7 CDL rats studied at the 24-hr time interval. Pretreatment with MDP appeared to reverse the impairment of phagocytic activity in the liver of CDL rats returning it to the level of sham animals (P < 0.05). However, pretreatment with MDP did not enhance the cytotoxic activity of the MPS as evidenced by higher CFU of E. coli in the liver, lung, and spleen of CDL animals pretreated with MDP as compared to CDL animals that did not receive MDP pretreatment. This increase was only significant in the spleen. Therefore, we conclude that although initially pretreatment with an immunostimulant, MDP, reverses the phagocytic impairment of the liver in animals with obstructive jaundice, the cytotoxic abilities of MPS at 24 hr postinjection of E. coli are not enhanced by pretreatment with MDP. o mm Academic Press,
Inc.
INTRODUCTION
Medical Center at Dallas, Dallas, Texas 752359031 December 27, 1988
complications. Morbidity and mortality rates following these procedures remain high [l, 21. Recent data have shown impairment of mononuclear phagocyte system function (of which the liver provides BO-85% of activity), T-cell and B-cell lymphocyte function, and polymorphonuclear leukocyte function in animals and patients with obstructive jaundice [3-71. Enhancement of depressed immune function in patients with obstructive jaundice may decrease the perioperative morbidity and mortality associated with surgical therapy for this disease. Muramyl dipeptide (MDP), a fragment of the mycobacterial cell wall, has been demonstrated to increase clearance of carbon particles by the liver in normal mice [8] and clearance of microaggregated human albumin in rats with obstructive jaundice [9]. The purpose of this study was to examine the uptake of intravenously injected Escherichia coli by the mononuclear phagocyte system in rats with obstructive jaundice and determine if pretreatment with MDP could improve this uptake. A second goal of this study was to determine the cytotoxic ability of the mononuclear phagocyte system during the 24 hr following E. coli injection in animals pretreated with MDP. MATERIALS
AND
METHODS
Animals Sixty-two 200- to 250-g male Sprague-Dawley rats (SASCO, Inc., Omaha, NE) were studied. The animals were housed five to a cage and were fed standard rat chow (Purina) and given water ad lib. during the preoperative and postoperative periods. Animals were cared for according to the guidelines of The University of Texas Southwestern Medical Center at Dallas. Operative Procedure
Surgical, radiologic, and endoscopic intervention in the patient with obstructive jaundice is fraught with infectious
Thirty-three animals underwent a 2-cm upper midline laparotomy with inhalational methoxyflurane anesthesia (Pitman-Moore, Inc., Washington Crossing, NJ). The proximal common bile duct was isolated between two 40 silk sutures (Ethicon, Inc., Somerville, NJ), ligated,
1 Please address correspondence and reprint requests to Charles W. Dunn, M.D., % Jureta W. Horton, Ph.D., Department of Surgery, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75235-9031. 249
0022.4804/90
$1.50
Copyright 0 1990 by Academic Press, Inc. All rights of reproduction in any form reserved.
250
JOURNAL
OF SURGICAL
RESEARCH:
VOL. 48, NO. 3, MARCH
and divided (CDL rats). Care was taken not to injure or obstruct the pancreatic duct. The abdomen was closed with interrupted 3-O prolene suture (Ethicon, Inc.) and the skin was closed with staples (Ethicon, Inc.). Twentynine animals had the same surgical procedure with isolation but not ligation of the common bile duct and were closed in the same fashion (sham rats). Animals were returned to their cages with liberal access to food and water and were studied 21 days after ligation or sham ligation. Weights were obtained prior to operative procedure and after 21 days in all animals.
Group 1
Bacterial Inoculum
Sham n=6
E. coli (encapsulated clinical isolate) was incubated in tryptic soy broth for 18 hr at 37°C. The bacterial suspension was centrifuged at 4800 rpm for 15 min and the precipitate was washed twice in phosphate-buffered saline (PBS) and resuspended in 5 ml of sterile PBS (pH 7.2, 0.15 M 8.00 g liter-’ NaCl, 0.20 g liter-’ KCl, 0.008 M 1.15 g liter-’ Na2HP04, 0.20 g liter-’ KH,PO,). The formal bacterial concentration was prepared against optical standards and confirmed by back plating of serial dilutions. All animals were injected with 1.0-3.5 X lo6 E. coli via the lateral tail vein. Experimental
Protocol
Animals were studied at 30 min and 24 hr postinjection of E. coli in groups as shown in Table 1. Phagocytic activity (30 min postinjection of E. coli). Preliminary studies in our laboratory using serial blood cultures obtained via direct cardiac puncture determined that injected E. coli was cleared from the blood in sham and CDL rats within 20 min as indicated by sterile blood cultures. Animals were, therefore, sacrificed 30 min postinjection of E. coli to determine phagocytic activity of the mononuclear phagocyte system of the liver, lung, and spleen. Six sham (Group 2) and 10 CDL rats (Group 4) were pretreated with MDP 3 pg/g (Sigma Chemical Co., St. Louis, MO) via subcutaneous injection 24 hr prior to bacterial injection. MDP was suspended in 10 cc sterile normal saline at a concentration of 2500 pg/ml. Ten sham (Group 1) and 10 CDL (Group 3) rats were not pretreated with MDP. Cytotoxic activity (24 hr postinjection of E. coli). Animals were sacrificed 24 hr postinjection of E. coli to determine the cytotoxic activity of the mononuclear phagocyte system in the liver, lung, and spleen. Seven sham (Group 6) and seven CDL rats (Group 8) were pretreated with MDP (3 pg/g) via subcutaneous injection 24 hr prior to bacterial injection as described above. Six sham (Group 5) and six CDL rats (Group 7) were not pretreated with MDP. Preparation of liver, lung, and spleen. The liver, lung, and spleen comprise the vast majority of the mononuclear phagocytic system and were studied to determine phago-
1990
TABLE Experimental
1 Protocol
Phagocytic activity 30 min postinjection of E. coli Group 2 Group 3
Sham n = 10
Sham + MDP n=6
CDL n = 10
Cytotoxic activity 24 hr postinjection of E. coli Group 6 Group 7
Group 5
Sham + MDP n=7
Note. MDP, muramyl
dipeptide;
CDL n=6
Group 4 CDL + MDP n = 10
Group 8 CDL + MDP n=7
CDL, common duct ligation.
cytic and cytotoxic activities. Animals were sacrificed via barbiturate overdose (Nembutal, Abbott Laboratories, North Chicago, IL). The liver, lungs, and spleen were aseptically harvested, washed with sterile saline, and weighed. The organs were ground in sterile PBS using a tissue grinder (V&is Co., Gardiner, NY) for 3 min. The tissue grinder was flamed with 90% alcohol between organs. Five milliliters of homogenate was transferred to individual sterile glass homogenizers (Wheaton Co., Carrollton, TX) and further ground to disrupt the cell membranes. After adequate homogenization was obtained, O.lml aliquots were serially diluted and plated on MacConkey’s agar (Austin Biological Labs, Austin, TX) and placed in the incubator at 37°C. Eighteen to 24 hr later, colony-forming units (CFU) were counted for each organ and only plates with 30-300 colonies were used for analysis. Liver function tests and bile cultures. In a preliminary study, 9 sham and 14 CDL rats were studied 21 days after sham ligation or common duct ligation. Blood was drawn via direct cardiac puncture and analyzed for albumin, total protein, alkaline phosphatase, total bilirubin, y-glutaryl transferase (GGT) and serum glutamic-pyruvate transaminase (SGPT). None of these animals were treated with MDP. In addition, aspiration cultures of bile from the obstructed bile ducts of the CDL animals were plated on MacConkey’s agar and incubated at 37°C for 24 hr. Statistical
Analysis
Two-way analysis rection was used to 24 hr time intervals. concentration of E. mean (SEM).
of variance with a Bonferroni coranalyze data at the 30-min and the All CFU data are expressed as log10 colilorgan + standard error of the RESULTS
Biochemistry Liver function tests were significantly elevated in the CDL animals vs the sham animals (P < 0.05). The total
DUNN
TABLE Liver
Function
AND
MDP
IN OBSTRUCTIVE
Tests and Serum
5.15 + .15 2.93 + .Ol 574 * 21
6.18 + .09 84.7 k 3.4 434 + 28
251
JAUNDICE
TABLE
2
CDL (n = 14) Total protein (g/dl) Albumin (g/dl) Alkaline phosphatase (III/liter) Total bilirubin (mg/dl) GGT (III/liter) SGPT (W/liter)
HORTON:
Organ
Proteins SHAM 5.35 3.36 428 0.1
3
Weights 21 Days after Sham Ligation Common Duct Ligation
or
(n = 9) f f f f
.02 .02* 40* .01*
5.4 + .4* 100 f 15*
Note. Data are expressed as means + SEM. * Indicates significant
Note. Data are expressed as means + SEM. GGT, y-glutaryl transferase; SGPT, serum glutamic-pyruvate transaminase; CDL, common duct ligation. * Indicates a significant difference between groups at P < 0.05.
protein in the CDL group was not significantly different than that seen in the sham group. Serum albumin was significantly lower after 21 days of obstructive jaundice in the CDL group vs that in the sham group (P < 0.05; Table 2). All cultures of bile were sterile.
9.9 f .2* 1.46 f .04* 0.76 f .02*
25.6 t- 1.1 3.07 f .05 2.70 f .14
Liver Lung Spleen
difference
between groups at P < 0.05.
CDL animals were pretreated with MDP. The CFU in the liver (6.43 + .52), lung (5.40 + .33), and spleen (5.75 t .32) of animals pretreated with MDP were greater than in CDL animals not receiving MDP pretreatment but did not reach statistical significance except in the spleen. Sham animals pretreated with MDP had no bacteria cul-
SHAM vs. CDL Weight Differences While weight gain over the 21 days after CDL tended to be less (from 234.4 + 1.1 to 287.8 +- 2.7 g, an 18% increase) than weight gain in the sham-operated rats (from 240.9 f 3.8 to 309.6 + 9.1, a 23% increase) this difference failed to achieve statistical significance. In contrast, the CDL group showed a significantly greater increase in liver, lung, and spleen organ weights after 21 days of obstruction compared to organ weight change in sham animals (P < 0.05; Table 3).
LIVER
LUNG
SPLEEN
CDL + MDP vs. CDL Quantitative Tissue Cultures at 30 min Postinjection of E. Coli (Fig. 1) CDL for 21 days significantly reduced the uptake of injected E. coli in the liver while the uptake of E. coli in the lungs was significantly greater than that measured in the sham group (P < 0.05). In the CDL animals, MDP pretreatment further enhanced uptake of E. coli by the liver resulting in a significant difference in liver uptake of E. coli between untreated and MDP-pretreated rats with common duct ligation (P < 0.05). Compared to untreated sham rats, 24-hr pretreatment of sham animals with MDP significantly increased the uptake of E. coli in the liver, lung, and spleen (P < 0.05). Quantitative Tissue Cultures at 24 hr Postinjection of E. Coli (Fig. 2) In the sham group, no bacteria could be cultured from the liver or lung 24 hr postinjection with 4.20 & .09 CFU noted in the spleen. This is in contrast to the CDL group where E. coli was cultured (liver, 4.73 + .46; lung, 4.36 -+ .35; spleen, 4.51 f .05) 24 hr after injection. The difference in splenic CFU/organ was not significant when
LIVER
LUNG
SPLEEN
SHAM vs. SHAM + MDP l
p < o,05 n
SHAM
(N=iO)
0 SHAM + MDP (N&)
6.1 1 *;05
5.01
5.40 I
~~~
LIVER
LUNG
SPLEEN
FIG. 1. Phagocytic activity. Data are expressed as means f SEM log concentration CFU/organ of E. coli. CDL, common duct ligation; MDP, muramyl dipeptide. *Indicates significant difference at P < 0.05.
252
JOURNAL
OF SURGICAL
RESEARCH:
SHAM vs. CDL ’ P < 0.06
LIVER
n
SHAM (N=6) 0 CDL (N=6)
LUNG
SPLEEN
CDL + MDP vs. CDL l
‘9
p
OF SURGICAL
RESEARCH
48, 249-253 (1990)
Muramyl Dipeptide Improves Mononuclear Phagocyte System Function in Obstructive Jaundice CHARLES W. DUNN, M.D.,’ AND JURETA W. HORTON, PH.D. With the technical assistance of Paula B. Walker, B.S. Department
of Surgery, University
of Texas Southwestern
Submitted
for publication
Previous studies have demonstrated depression of the mononuclear phagocyte system (MPS) of which the liver comprises SO-85% in animals subjected to 2 1 days of obstructive jaundice. This study examined the ability of a macrophage stimulant, muramyl dipeptide (MDP), to reverse MPS dysfunction in an obstructive jaundice rat model. Sixty-two male Sprague-Dawley rats underwent sham (n = 29) laparotomy or common duct ligation (CDL) (n = 33) and were studied after 21 days. Animals were injected with l-3.5 X 10’ Escherichia coli via a lateral tail vein, and colony-forming units (CFU) of the liver, lung, and spleen were determined at two time intervals: 30 min postinjection to determine the phagocytic activity of MPS (sham, n = 16; CDL, n = 20) and 24 hr postinjection to determine cytotoxic activity of MPS (sham, n = 13; CDL, n = 13). MDP (3 pg/g) was administered subcutaneously 24 hr prior to E. coli injection in 6 sham and 10 CDL rats studied at the 30-min time interval and 7 sham and 7 CDL rats studied at the 24-hr time interval. Pretreatment with MDP appeared to reverse the impairment of phagocytic activity in the liver of CDL rats returning it to the level of sham animals (P < 0.05). However, pretreatment with MDP did not enhance the cytotoxic activity of the MPS as evidenced by higher CFU of E. coli in the liver, lung, and spleen of CDL animals pretreated with MDP as compared to CDL animals that did not receive MDP pretreatment. This increase was only significant in the spleen. Therefore, we conclude that although initially pretreatment with an immunostimulant, MDP, reverses the phagocytic impairment of the liver in animals with obstructive jaundice, the cytotoxic abilities of MPS at 24 hr postinjection of E. coli are not enhanced by pretreatment with MDP. o mm Academic Press,
Inc.
INTRODUCTION
Medical Center at Dallas, Dallas, Texas 752359031 December 27, 1988
complications. Morbidity and mortality rates following these procedures remain high [l, 21. Recent data have shown impairment of mononuclear phagocyte system function (of which the liver provides BO-85% of activity), T-cell and B-cell lymphocyte function, and polymorphonuclear leukocyte function in animals and patients with obstructive jaundice [3-71. Enhancement of depressed immune function in patients with obstructive jaundice may decrease the perioperative morbidity and mortality associated with surgical therapy for this disease. Muramyl dipeptide (MDP), a fragment of the mycobacterial cell wall, has been demonstrated to increase clearance of carbon particles by the liver in normal mice [8] and clearance of microaggregated human albumin in rats with obstructive jaundice [9]. The purpose of this study was to examine the uptake of intravenously injected Escherichia coli by the mononuclear phagocyte system in rats with obstructive jaundice and determine if pretreatment with MDP could improve this uptake. A second goal of this study was to determine the cytotoxic ability of the mononuclear phagocyte system during the 24 hr following E. coli injection in animals pretreated with MDP. MATERIALS
AND
METHODS
Animals Sixty-two 200- to 250-g male Sprague-Dawley rats (SASCO, Inc., Omaha, NE) were studied. The animals were housed five to a cage and were fed standard rat chow (Purina) and given water ad lib. during the preoperative and postoperative periods. Animals were cared for according to the guidelines of The University of Texas Southwestern Medical Center at Dallas. Operative Procedure
Surgical, radiologic, and endoscopic intervention in the patient with obstructive jaundice is fraught with infectious
Thirty-three animals underwent a 2-cm upper midline laparotomy with inhalational methoxyflurane anesthesia (Pitman-Moore, Inc., Washington Crossing, NJ). The proximal common bile duct was isolated between two 40 silk sutures (Ethicon, Inc., Somerville, NJ), ligated,
1 Please address correspondence and reprint requests to Charles W. Dunn, M.D., % Jureta W. Horton, Ph.D., Department of Surgery, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75235-9031. 249
0022.4804/90
$1.50
Copyright 0 1990 by Academic Press, Inc. All rights of reproduction in any form reserved.
250
JOURNAL
OF SURGICAL
RESEARCH:
VOL. 48, NO. 3, MARCH
and divided (CDL rats). Care was taken not to injure or obstruct the pancreatic duct. The abdomen was closed with interrupted 3-O prolene suture (Ethicon, Inc.) and the skin was closed with staples (Ethicon, Inc.). Twentynine animals had the same surgical procedure with isolation but not ligation of the common bile duct and were closed in the same fashion (sham rats). Animals were returned to their cages with liberal access to food and water and were studied 21 days after ligation or sham ligation. Weights were obtained prior to operative procedure and after 21 days in all animals.
Group 1
Bacterial Inoculum
Sham n=6
E. coli (encapsulated clinical isolate) was incubated in tryptic soy broth for 18 hr at 37°C. The bacterial suspension was centrifuged at 4800 rpm for 15 min and the precipitate was washed twice in phosphate-buffered saline (PBS) and resuspended in 5 ml of sterile PBS (pH 7.2, 0.15 M 8.00 g liter-’ NaCl, 0.20 g liter-’ KCl, 0.008 M 1.15 g liter-’ Na2HP04, 0.20 g liter-’ KH,PO,). The formal bacterial concentration was prepared against optical standards and confirmed by back plating of serial dilutions. All animals were injected with 1.0-3.5 X lo6 E. coli via the lateral tail vein. Experimental
Protocol
Animals were studied at 30 min and 24 hr postinjection of E. coli in groups as shown in Table 1. Phagocytic activity (30 min postinjection of E. coli). Preliminary studies in our laboratory using serial blood cultures obtained via direct cardiac puncture determined that injected E. coli was cleared from the blood in sham and CDL rats within 20 min as indicated by sterile blood cultures. Animals were, therefore, sacrificed 30 min postinjection of E. coli to determine phagocytic activity of the mononuclear phagocyte system of the liver, lung, and spleen. Six sham (Group 2) and 10 CDL rats (Group 4) were pretreated with MDP 3 pg/g (Sigma Chemical Co., St. Louis, MO) via subcutaneous injection 24 hr prior to bacterial injection. MDP was suspended in 10 cc sterile normal saline at a concentration of 2500 pg/ml. Ten sham (Group 1) and 10 CDL (Group 3) rats were not pretreated with MDP. Cytotoxic activity (24 hr postinjection of E. coli). Animals were sacrificed 24 hr postinjection of E. coli to determine the cytotoxic activity of the mononuclear phagocyte system in the liver, lung, and spleen. Seven sham (Group 6) and seven CDL rats (Group 8) were pretreated with MDP (3 pg/g) via subcutaneous injection 24 hr prior to bacterial injection as described above. Six sham (Group 5) and six CDL rats (Group 7) were not pretreated with MDP. Preparation of liver, lung, and spleen. The liver, lung, and spleen comprise the vast majority of the mononuclear phagocytic system and were studied to determine phago-
1990
TABLE Experimental
1 Protocol
Phagocytic activity 30 min postinjection of E. coli Group 2 Group 3
Sham n = 10
Sham + MDP n=6
CDL n = 10
Cytotoxic activity 24 hr postinjection of E. coli Group 6 Group 7
Group 5
Sham + MDP n=7
Note. MDP, muramyl
dipeptide;
CDL n=6
Group 4 CDL + MDP n = 10
Group 8 CDL + MDP n=7
CDL, common duct ligation.
cytic and cytotoxic activities. Animals were sacrificed via barbiturate overdose (Nembutal, Abbott Laboratories, North Chicago, IL). The liver, lungs, and spleen were aseptically harvested, washed with sterile saline, and weighed. The organs were ground in sterile PBS using a tissue grinder (V&is Co., Gardiner, NY) for 3 min. The tissue grinder was flamed with 90% alcohol between organs. Five milliliters of homogenate was transferred to individual sterile glass homogenizers (Wheaton Co., Carrollton, TX) and further ground to disrupt the cell membranes. After adequate homogenization was obtained, O.lml aliquots were serially diluted and plated on MacConkey’s agar (Austin Biological Labs, Austin, TX) and placed in the incubator at 37°C. Eighteen to 24 hr later, colony-forming units (CFU) were counted for each organ and only plates with 30-300 colonies were used for analysis. Liver function tests and bile cultures. In a preliminary study, 9 sham and 14 CDL rats were studied 21 days after sham ligation or common duct ligation. Blood was drawn via direct cardiac puncture and analyzed for albumin, total protein, alkaline phosphatase, total bilirubin, y-glutaryl transferase (GGT) and serum glutamic-pyruvate transaminase (SGPT). None of these animals were treated with MDP. In addition, aspiration cultures of bile from the obstructed bile ducts of the CDL animals were plated on MacConkey’s agar and incubated at 37°C for 24 hr. Statistical
Analysis
Two-way analysis rection was used to 24 hr time intervals. concentration of E. mean (SEM).
of variance with a Bonferroni coranalyze data at the 30-min and the All CFU data are expressed as log10 colilorgan + standard error of the RESULTS
Biochemistry Liver function tests were significantly elevated in the CDL animals vs the sham animals (P < 0.05). The total
DUNN
TABLE Liver
Function
AND
MDP
IN OBSTRUCTIVE
Tests and Serum
5.15 + .15 2.93 + .Ol 574 * 21
6.18 + .09 84.7 k 3.4 434 + 28
251
JAUNDICE
TABLE
2
CDL (n = 14) Total protein (g/dl) Albumin (g/dl) Alkaline phosphatase (III/liter) Total bilirubin (mg/dl) GGT (III/liter) SGPT (W/liter)
HORTON:
Organ
Proteins SHAM 5.35 3.36 428 0.1
3
Weights 21 Days after Sham Ligation Common Duct Ligation
or
(n = 9) f f f f
.02 .02* 40* .01*
5.4 + .4* 100 f 15*
Note. Data are expressed as means + SEM. * Indicates significant
Note. Data are expressed as means + SEM. GGT, y-glutaryl transferase; SGPT, serum glutamic-pyruvate transaminase; CDL, common duct ligation. * Indicates a significant difference between groups at P < 0.05.
protein in the CDL group was not significantly different than that seen in the sham group. Serum albumin was significantly lower after 21 days of obstructive jaundice in the CDL group vs that in the sham group (P < 0.05; Table 2). All cultures of bile were sterile.
9.9 f .2* 1.46 f .04* 0.76 f .02*
25.6 t- 1.1 3.07 f .05 2.70 f .14
Liver Lung Spleen
difference
between groups at P < 0.05.
CDL animals were pretreated with MDP. The CFU in the liver (6.43 + .52), lung (5.40 + .33), and spleen (5.75 t .32) of animals pretreated with MDP were greater than in CDL animals not receiving MDP pretreatment but did not reach statistical significance except in the spleen. Sham animals pretreated with MDP had no bacteria cul-
SHAM vs. CDL Weight Differences While weight gain over the 21 days after CDL tended to be less (from 234.4 + 1.1 to 287.8 +- 2.7 g, an 18% increase) than weight gain in the sham-operated rats (from 240.9 f 3.8 to 309.6 + 9.1, a 23% increase) this difference failed to achieve statistical significance. In contrast, the CDL group showed a significantly greater increase in liver, lung, and spleen organ weights after 21 days of obstruction compared to organ weight change in sham animals (P < 0.05; Table 3).
LIVER
LUNG
SPLEEN
CDL + MDP vs. CDL Quantitative Tissue Cultures at 30 min Postinjection of E. Coli (Fig. 1) CDL for 21 days significantly reduced the uptake of injected E. coli in the liver while the uptake of E. coli in the lungs was significantly greater than that measured in the sham group (P < 0.05). In the CDL animals, MDP pretreatment further enhanced uptake of E. coli by the liver resulting in a significant difference in liver uptake of E. coli between untreated and MDP-pretreated rats with common duct ligation (P < 0.05). Compared to untreated sham rats, 24-hr pretreatment of sham animals with MDP significantly increased the uptake of E. coli in the liver, lung, and spleen (P < 0.05). Quantitative Tissue Cultures at 24 hr Postinjection of E. Coli (Fig. 2) In the sham group, no bacteria could be cultured from the liver or lung 24 hr postinjection with 4.20 & .09 CFU noted in the spleen. This is in contrast to the CDL group where E. coli was cultured (liver, 4.73 + .46; lung, 4.36 -+ .35; spleen, 4.51 f .05) 24 hr after injection. The difference in splenic CFU/organ was not significant when
LIVER
LUNG
SPLEEN
SHAM vs. SHAM + MDP l
p < o,05 n
SHAM
(N=iO)
0 SHAM + MDP (N&)
6.1 1 *;05
5.01
5.40 I
~~~
LIVER
LUNG
SPLEEN
FIG. 1. Phagocytic activity. Data are expressed as means f SEM log concentration CFU/organ of E. coli. CDL, common duct ligation; MDP, muramyl dipeptide. *Indicates significant difference at P < 0.05.
252
JOURNAL
OF SURGICAL
RESEARCH:
SHAM vs. CDL ’ P < 0.06
LIVER
n
SHAM (N=6) 0 CDL (N=6)
LUNG
SPLEEN
CDL + MDP vs. CDL l
‘9
p
