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Department of Surgery, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Department of Surgery, University of Texas at Dallas Southwestern Medical Center, Dallas 75235; and Dallas Department of Veterans Affairs Medical Center, Dallas, Texas 75216
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
ACKNOWLEDGEMENTS
FOOTNOTES
REFERENCES
ABSTRACT 
Rothenbach, Patricia, Richard H. Turnage, Jose Iglesias,
Angela Riva, Lori Bartula, and Stuart I. Myers. Downstream effects
of splanchnic ischemia-reperfusion injury on renal function and
eicosanoid release. J. Appl. Physiol.
82(2): 530-536, 1997.
This study examines the hypothesis that
intestinal ischemia-reperfusion (I/R) injury contributes to renal
dysfunction by altered renal eicosanoid release. Anesthetized
Sprague-Dawley rats underwent 60 min of sham or superior mesenteric
artery (SMA) occlusion with 60 min of reperfusion. The I/R groups
received either allopurinol, pentoxifylline, 1-benzylimidazole, or
carrier before SMA occlusion. In vivo renal artery blood flow was
measured by Transonic flow probes, the kidneys were then perfused in
vitro for 30 min, and the effluent was analyzed for eicosanoid release
and renal function. Intestinal I/R caused a twofold increase in the
ratio of renal release of thromboxane
B2 to prostaglandin
E2 and to 6-ketoprostaglandin F1
compared with the sham
level, with a corresponding 25% decrease in renal sodium and inulin
clearance and renal blood flow. Pentoxifylline or allopurinol
pretreatment restored renal eicosanoid release and renal sodium and
inulin clearance to the sham level but did not alter renal blood flow.
Pretreatment with 1-benzylimidazole restored renal function, eicosanoid
release, and renal blood flow to sham levels. These data suggest that
severe intestinal I/R contributes to the downregulation of renal
function. The decrease in renal function is due in part to toxic oxygen metabolites, which occur in the milieu of altered renal eicosanoid release, reflecting a decrease in vasodilator and an increase in
vasoconstrictor eicosanoids.
renal eicosanoid release; renal blood flow
INTRODUCTION THE KIDNEY has been previously shown to be a
significant site of vasoactive prostanoid release, and endogenous renal
prostanoids have been implicated as mediators of renal vascular
resistance in normal and pathological states (7, 29, 30,
54). Several animal models have shown that the kidney
responds to many varied types of injury (hemorrhagic shock,
hydronephrosis, hypoxia, acute tubular necrosis, and sepsis) by
altering net endogenous eicosanoid release to reflect a net increase in
the synthesis of vasoconstrictor eicosanoids compared with endogenous
synthesis of vasodilator eicosanoids (7, 29, 30, 40-42, 54, 55).
The findings of these studies support the notion that vasodilator
eicosanoids contribute to maintaining normal intrarenal blood flow and
that either loss of endogenous vasodilator eicosanoids or increased synthesis of vasoconstrictor eicosanoids (or a combination of both
scenarios) contributes to decreased intrarenal blood flow in
pathological states (6, 21-23, 30, 33, 34, 40-42, 49, 55).
Pentoxifylline (Ptx) has been shown to increase survival and preserve
renal function after ischemia-reperfusion (I/R) injury. Although the specific protective mechanism of Ptx on renal function and
eicosanoid release after intestinal I/R injury has not been investigated, several studies have suggested that the beneficial effect
of Ptx includes increased tissue oxygenation, increased oxygen
consumption, and decreased leukocyte adhesiveness and subsequent prevention of the release of toxic substances from leukocytes, including oxygen-derived free radicals (5, 16, 39, 51).
Allopurinol has been shown in studies investigating I/R injury to
prevent superoxide radical release after conversion of hypoxanthine to
xanthine in ischemic tissue during reperfusion (4, 8, 15, 17-20,
28, 43). Several studies have shown that xanthine oxidase was present
in renal and intestinal tissue and that allopurinol could prevent
injury to both organs after I/R injury (17-20, 28).
Several published reports have documented distant organ dysfunction
after acute trauma or injury (10, 21, 23a, 24, 38, 45). The majority of
these studies have shown that distant trauma or injury leads to
progressive pulmonary injury. The pulmonary injury after remote injury
was associated with increased pulmonary vasoconstrictor eicosanoid
release (10, 23, 45). These studies hypothesized that burn or
intestinal I/R injury induces the release of various mediators such as
eicosanoids, activated neutrophils, and cytokines, which contribute to
distant lung injury. These studies have not determined whether burn
injury or intestinal I/R injury can alter renal eicosanoid release and
renal function. This study examines the hypothesis that severe
mesenteric I/R injury alters renal eicosanoid release and renal
function.
MATERIALS AND METHODS Surgical Model
Preparation of the Rat for I/R Injury and In Vivo Aortic and Renal Artery Blood Flow
The animals of the sham group received an injection of 0.05 ml saline carrier 10 min before SMA occlusion and 1 min before clip removal (31, 39). The Ptx I/R groups received either an injection of 0.05 ml saline carrier (SMA I/R) or 0.05 ml of saline containing 50 mg/kg Ptx iv (SMA I/R + Ptx) 10 min before microvascular clipping of SMA and occlusion of collateral vessels and 1 min before clip removal, as previously described (31, 39). The imidazole group of animals received 0.5 ml of saline or saline containing 50 mg/kg of 1-benzylimidazole 2 min before SMA clipping (SMA I/R + imidazole) (40-42, 54, 55). The allopurinol groups received either saline carrier (pH adjusted to 10.5 with 1 N NaOH) or allopurinol 50 mg/kg by gavage for 3 days. After the dose of allopurinol on the third day, rats underwent intestinal I/R as described in Surgical Model (SMA I/R + allopurinol). All rats were studied for identical time periods regardless of group assignment. The SMA clip was removed after 60 min. At this time, a second dose of 0.05 ml saline was given to the sham and SMA I/R groups and 0.05 ml of Ptx (50 mg/kg) was administered to the SMA I/R + Ptx group, and the bowel was reperfused for 60 min (39).All animals had measurement of renal and abdominal aortic blood flow by mean transmittable Doppler flowmeters (1RB109 and 2SB73, Transonic systems, Ithaca, NY) as described by Bailey et al. (2), Drost (11), and Myers and Hernandez (37). Blood flow measurements were made before intestinal I/R and then at 15 min after intestinal I/R (total of 135 min) and were recorded as milliliters per minute. The data are presented as renal blood flow as a percentage of aortic blood flow (means ± SE).
Preparation of the In Vitro Isolated Mesenteric Perfusion
After the 135 min of intestinal I/R described in Preparation of the Rat for I/R Injury and In Vivo Aortic and Renal Artery Blood Flow, the renal arteries were rapidly cannulated and removed with the intact kidney (34, 40-42, 54, 55). The kidney was perfused in vitro as described below. The right kidney was perfused with oxygenated Krebs-Henseleit (95% O2-5% CO2, PO2 460 ± 10 Torr) buffer (alone). The left kidney was perfused with modified Krebs-Henseleit (without dextrose) containing 2 mg/ml of inulin and 6.7 mM of lactic acid. The imidazole-treated groups were perfused in vitro with Krebs-Henseleit buffer containing 50 mg/ml 1-benzylimidazole. Both kidneys were perfused at a rate of 3 ml/min with a Cole-Palmer peristaltic pump (Chicago, IL) at 37°C (pH 7.40). Perfusion pressures were monitored via a sidearm of the arterial cannula by using a Digi-Med blood pressure analyzer. The renal venous effluent was collected at 30 min. Samples were collected in plastic microcentrifuge tubes and immediately frozen at
20°C until assayed by enzyme immunoassay technique.
Enzyme Immunoassay
Venous effluent was analyzed for thromboxane B2 [TxB2; stable end product of thromboxane A2 (TxA2)], prostaglandin E2 (PGE2), and 6-ketoprostaglandin F1
[6-keto-PGF1; stable end product of prostaglandin I2
(PGI2)] by enzyme
immunoassay as previously described (40, 44). The
6-keto-PGF1 and
TxB2 enzyme immunoassay reagents
were purchased from Cayman Chemical (Ann Arbor, MI), and the
PGE2 reagents were purchased from
Oxford Biomedical (Oxford, MI).
Protein Immunoblot Analysis of Prostacyclin Synthase and Cyclooxygenase-1
Kidney cortex and medulla were separated and homogenized in 0.1 M KPO4, pH 7.4, buffer containing 10 mM EDTA and 1 mM dithiothreitol. Total cellular proteins (50 µg) were separated by 7% polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and transferred onto nitrocellulose filters (Schleicher and Schuell, Keene, NH) (3, 9, 14, 35, 36, 48). The filters were blocked for 1 h at room temperature in 100 ml phosphate-buffered saline (PBS) containing 0.05% Tween 20, 0.5 M NaCl, and 1% bovine serum albumin (BSA) (buffer A) and incubated overnight at room temperature in the same solution containing either a rabbit
-cyclooxygenase-1 or
thromboxane synthase immunoglobulin G (IgG) (Cayman Chemical) (24, 35,
36) or a rabbit -prostacyclin synthase IgG (1:10,000, vol/vol)
(kindly provided by Dr. William L. Smith, Michigan State Univ., East
Lansing, MI) (35, 36). Filters were washed two times for
20 min in buffer A at room temperature
and then one time for 20 min in PBS containing 0.5M NaCl and 1% BSA
(buffer B). The blots were incubated
2 h at room temperature in 100 ml buffer
B containing 10 µCi
125I-labeled
protein A (specific activity 1,110 mBq/mg), washed two times for 20 min in buffer
B, and finally washed for 20 min in PBS.
Immunoreactions were developed by autoradiography overnight at
70°C. Autoradiograms were scanned by using the
LKB2222-020 UltroScan XL laser densitometer at 633 nm (35,
36). Peaks were integrated by using the LKB internal
integrator and line printer. Replicate scans were within ±1.00%
and were background corrected. The mean peak areas were
calculated.
Quantification of Renal Function in the Isolated Perfused Rat Kidney
The renal function of the isolated perfused rat kidneys was analyzed by examining renal sodium clearance, renal inulin clearance, and fractional sodium excretion, as previously described, at 30 min of in vitro perfusion (26, 32, 40, 46, 50). Sodium clearance. Sodium from the urine and perfusate (Krebs buffer) was measured on Beckman Astra-8-3000 (Beckman Instruments, Houston, TX), and sodium clearance was calculated as (urine sodium; mmol/l) · (volume of urine; ml/min)/(Krebs sodium; mmol/l) and expressed as means ± SE (ml/min). Inulin clearance. Inulin (Sigma Chemical, St. Louis, MO) stock solution was prepared in water and subsequently diluted with Krebs-Henseleit buffer to a concentration of 0.2 mg/ml. The inulin-Krebs solution was infused at a rate that maintained renal perfusion pressure at 100 mmHg (3 ml/min), and urine was collected for 10 min at 30 min of perfusion. The urine volumes were measured and diluted 1:10 in 10% trichloroacetic acid and centrifuged at 2,000 revolutions/min for 10 min. The supernatant was used to assay for inulin. Anthrone reagent (Sigma Chemical) was prepared in 70% sulfuric acid at a concentration of 2 mg/ml. Then, 200 µl of unknowns, standards, and Krebs blank were added to 2 ml of the Anthrone reagent and heated for 10 min at 57°C. Assay tubes were then cooled to room temperature and read at 620 nm on a Beckman DU50 spectrophotometer. Unknown sample concentrations were extrapolated from a standard inulin curve, and glomerular filtration rate was calculated as [urine inulin (mg/ml) · volume urine (ml/min)]/Krebs inulin (mg/ml) and expressed as means ± SE (ml/min). Fractional sodium excretion. Fractional sodium excretion is expressed as a percentage in this study and was calculated as sodium clearance/inulin clearance × 100 and expressed as means ± SE.Statistical Analysis
Eicosanoid release data are calculated as nanograms per minute and are reported as the ratios of TxB2 to PGE2 and of TxB2 to 6-keto-PGF1. Renal function
data are presented as milliliters per minute for sodium clearance and
inulin clearance and as percent for sodium excretion. In vivo renal
artery blood flow is presented as a percentage of total aortic blood
flow. Eicosanoid release data and renal function data are presented as
means ± SE for six rats at 30 min of perfusion.
Statistical significance is accepted at
P < 0.05 with comparisons made by
using analysis of variance and Duncan's post hoc test or Student's
t-test. Renal blood flow data are presented as
means ± SE for six rats at 15 min after I/R. The immunoblot data
are presented as means ± SE for four rats and analyzed by
Student's t-test.
RESULTS
Intestinal I/R produced a ninefold increase in the ratio of the renal
release of TxB2 to
PGE2 compared with the sham group at 30 min of perfusion (Fig. 1). The
increased ratio of release of TxB2
to PGE2 was due to a significant
increase in the renal release of
TxB2 and to a marked
decrease in the renal release of
PGE2 (Table
1). In the I/R groups that received Ptx or
allopurinol pretreatment, the ratio of renal release of
TxB2 to
PGE2 remained at the sham level
(Fig. 1, Table 1).
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Intestinal I/R also caused a twofold increase in the ratio of renal
release of TxB2 to
6-keto-PGF1 compared with the sham group at 30 min of perfusion. This twofold increase in the ratio
of renal release of TxB2 to
6-keto-PGF1 was almost entirely
secondary to the increased release of
TxB2 (Table 1). The increased
ratio of the renal release of TxB2
to 6-keto-PGF1 after intestinal
I/R was prevented by pretreatment with Ptx or allopurinol (Fig.
2).
(6-keto-PGF1) in in vitro
perfused rat kidney. Rats received Ptx (stippled bar), allopurinol
(crosshatched bar), or carrier (open bar); were subjected to SMA
occlusion and reperfusion (solid bar), as described in MATERIALS AND METHODS; and were
compared with sham controls (open bar). Venous effluent was collected
at 30 min of perfusion and assayed for
TxB2 (thromboxane
A2 metabolite) and
6-keto-PGF1 (prostaglandin
I2 metabolite). Values are
calculated as picograms of TxB2 or
6-keto-PGF1 released per
milliliter and are expressed as a ratio of renal release of
TxB2 to
6-keto-PGF1 as a percent. Values are means ± SE for 6 rats. * Significantly different
from Ptx, allopurinol, and sham groups,
P < 0.05 (by analysis of variance and Duncan's post hoc test.)
Sodium clearance and inulin clearance of the rat kidney perfused in vitro with oxygenated Krebs at 30 min of perfusion after intestinal I/R were significantly decreased compared with the sham group. Ptx and allopurinol pretreatment prevented the decrease in sodium and inulin clearances after intestinal I/R injury (Table 2). Intestinal I/R did not significantly alter percent sodium excretion in the isolated perfused rat kidney at 30 min of perfusion. However, a downward trend was noted (Table 1).
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Mean arterial pressures were compared at 120 min in the sham group or
at 60 min after reperfusion in the I/R groups. Arterial pressure was 87 ± 6.5 mmHg in the sham group treated with Ptx and
107 ± 8 mmHg in the sham group treated with imidazole. Systolic pressure was not significantly altered by I/R (89 ± 6 mmHg).
Treatment of the I/R groups with Ptx significantly decreased arterial
pressure to 48 ± 8 mmHg compared with the sham group treated with
Ptx or the I/R groups (P < 0.05). Treatment of the I/R groups with either allopurinol or imidazole did not significantly alter arterial pressure
(56 ± 12 and 72 ± 7 mmHg, respectively) compared with sham groups
without drug treatment or sham groups treated with either allopurinol
or imidazole (90 ± 7 mmHg). Intestinal I/R injury decreased in vivo
renal artery blood flow by 25% when compared with sham-operated
controls (Fig. 3). Ptx or allopurinol
pretreatment did not alter renal artery blood flow after I/R injury
(Fig. 3).
Treatment of the sham animals with 1-benzylimidazole decreased
endogenous renal release of TxB2
but did not alter release of PGE2
or 6-keto-PGF1. Treatment of
the sham animals with 1-benzylimidazole did not alter renal function or
in vivo renal blood flow (Table
3). A separate group of animals was
subjected to intestinal I/R with saline carrier for comparison with the intestinal I/R group treated with 1-benzylimidazole. Intestinal I/R
treated with saline carrier increased renal release of
TxB2 and decreased renal release
of PGE2 concomitant with decreases in inulin and sodium clearance and in vivo renal blood
flow. These changes in renal eicosansoid release, renal
function, and renal blood flow were reversed by 1-benzylimidazole
pretreatment (Table 3).
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Intestinal I/R decreased the cyclooxygenase-1 content in the renal medulla by 30% compared with the sham group. Pretreatment with Ptx (or allopurinol, data not shown) did not prevent the decrease in cyclooxygenase-1 content in the intestinal I/R group (Table 4). Intestinal I/R did not alter thromboxane synthase content in the cortex or medulla. Renal cortical and medullary prostacyclin synthase content was below the level of detection, as was cortical cyclooxygenase-1 content (Table 4).
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DISCUSSION
Over the past 20 years, several studies have suggested that endogenous renal eicosanoids influence both renal vascular tone and urinary diuresis (6, 7, 23, 25, 29, 30, 33, 40-42, 49, 54, 55). These studies have shown PGE2 to be the primary eicosanoid synthesized and released by the kidney (7, 29). Several chronic models of renal pathology have demonstrated that the kidney responds to injury by an increased level of endogenous renal eicosanoid synthesis with an increased synthesis of TxA2 (vasoconstrictor eicosanoid) and a corresponding decrease in synthesis of PGE2 and PGI2 (vasodilator eicosanoids) (34, 41, 42, 54, 55). These studies support the notion that relative changes in vasoconstrictor and vasodilator eicosanoid release contribute to the increase in renal vascular resistance present in these models. This group of studies also suggests that 48 h is the time required to upregulate renal synthesis and release of TxA2 (54). In contrast, acute models have not shown an increase in TxA2 synthesis but rather a decreased release of PGE2 and PGI2. This finding was demonstrated in one study that compared the effects of hypoxic perfusion on in vitro renal eicosanoid release (40). In vitro perfusion of the rat kidney with oxygenated Krebs buffer (PO2 = 460 Torr) was compared with in vitro perfusion with hypoxic Krebs buffer (PO2 = 60 Torr). Myers et al. (40) showed that in vitro perfusion of the rat kidney decreased renal TxB2 significantly but did not alter renal PGE2 or PGI2 release. In other words, there was a relative decrease in the ratio of renal vasoconstrictor eicosanoids to renal vasodilator eicosanoids released by the kidney (40).
Several studies were specifically designed to investigate the effect of various injury models on distant organ dysfunction (6, 10, 21, 23, 38, 45). One group of studies examined the effect of intestinal I/R and burn injury on pulmonary dysfunction (10, 23, 45). Demling et al. (10) examined the effects of burn wounds on lung eicosanoid release. They found significant increases in pulmonary lymph and pulmonary arterial TxB2 levels due to increased TxB2 release from the burn tissue. The authors hypothesized that acute thermal injury increased burn tissue release of TxB2, which caused secondary injury to the lungs (10). Schmeling et al. (45) examined the effects of intestinal I/R on the lung. In their study, lung injury was assessed by measuring tissue adenosine triphosphate and myeloperoxidase values as well as by histological evaluation. Schmeling et al. demonstrated that intestinal I/R injury caused secondary lung injury by a decrease in tissue ATP, an increase in myeloperoxidase activity, neutrophil sequestration in the lungs, and increased microvascular permeability (45).
The present study utilized a similar approach as described by Schmeling et al. to investigate the effect of severe intestinal I/R on renal function and eicosanoid release. The data showed that severe acute mesenteric I/R injury markedly increased the relative release of endogenous renal vasoconstrictor to vasodilator eicosanoids and caused a parallel decrease in inulin and sodium clearance. Interestingly, acute intestinal I/R injury stimulated an increase in the release of endogenous TxB2 release and a fourfold decrease in PGE2 release after 2 h of injury. These findings could have great potential clinical significance because increased endogenous renal thromboxane release and decreased renal PGE2 release may be one of several unrecognized mechanisms contributing to acute renal failure after severe mesenteric I/R injury.
The increased ratio of the renal release of vasoconstrictor to vasodilator eicosanoids and the parallel decrease in renal function after severe intestinal I/R injury was prevented by Ptx, allopurinol, and 1-benzylimidazole pretreatment. Although severe intestinal I/R decreased total renal artery blood flow by 25%, these changes in renal artery blood flow were only prevented by pretreatment with 1-benzylimidazole and were not prevented by Ptx or allopurinol pretreatment. Although the mechanisms of this finding were not specifically examined in the present study, previous studies have provided some insight into the protective effects of Ptx treatment on visceral organ function after intestinal I/R injury (5, 16, 39, 51, 52). Myers et al. (39) examined the effects of Ptx on splanchnic PGI2 release after severe intestinal I/R injury. In that study, Ptx preserved splanchnic PGI2 release and significantly decreased intestinal histological injury (39). Flynn et al. (16) showed that Ptx preserved hepatic blood flow and function during resuscitation from hemorrhagic shock. The exact mechanisms of Ptx preservation of visceral organ protection after I/R injury are not known and are not the focus of this study. However, our study, when considered in the context of the previous studies mentioned above, suggests that Ptx prevents the renal injury after splanchnic I/R at the microvascular level and not at the level of total renal artery blood flow. Data from the allopurinol pretreatment group suggest that the renal microvascular injury after intestinal I/R is due in part to the production of toxic oxygen metabolites. The source of the oxygen-derived free radicals could be from circulating leukocytes activated by intestinal I/R or from within the kidney. The enzyme xanthine oxidase has been shown to be present in the intestine and the kidney (19, 20, 43). During ischemia, xanthine oxidase is transformed into xanthine dehydrogenase during ischemia, and concurrently ATP is converted in a series of steps into hypoxanthine. Hypoxanthine, in the presence of molecular oxygen, is converted by xanthine dehydrogenase into xanthine with concomitant release of the superoxide radical. The superoxide radical can then be converted by superoxide dismutase into hydrogen peroxide, which can be further metabolized into water and oxygen by the enzyme catalase (17-20, 28, 43). Allopurinol prevents the first series of reactions and thus prevents production of the superoxide radical. The site of action of allopurinol in our study could be the intestine (which would prevent leukocyte activation), the activated leukocytes, or the renal tissue. The 1-benzylimidazole data suggest that the increased endogenous renal release of thromboxane after intestinal I/R contributes to changes in renal blood flow. Although the site of action of increased endogenous thromboxane synthesis was not examined in this study, one could hypothesize that thromboxane contributed to vasoconstriction at the level of the renal arterioles.
The present study represents the first group of experiments to suggest that severe intestinal I/R induces a downregulation of renal function. The eicosanoid data from sham, I/R, and I/R groups pretreated with Ptx, allopurinol, and 1-benzylimidazole provide insight into the mechanisms of the remote renal injury. The decrease in renal function is associated with a relative increase in the ratio of renal vasoconstrictor to vasodilator eicosanoids and the exposure of the renal tissue to toxic oxygen metabolites. Although we cannot state the specific mechanisms of renal injury after intestinal I/R, we hypothesize that the renal tissue is exposed to toxic oxygen metabolites released from leukocytes activated by intestinal I/R. The exposure of renal tissue to toxic oxygen metabolites occurs in the milieu of altered renal eicosanoid release, which reflects both a fourfold decrease in PGE2, the principal endogenous renal vasodilator eicosanoid, and a twofold increase in release of TxB2, a potent vasoconstrictor. Several previous studies using cell-free systems or whole kidney provide support for the notion that oxygen-derived free radicals could contribute to the altered renal eicosanoid release found in our experimental model (1, 12, 13, 45, 53).
The immunoblot data provide some insight into the mechanisms involved with renal eicosanoid release after intestinal I/R. The rise in renal TxB2 release after intestinal I/R was not due to an increase in content of thromboxane synthase and occurred despite a 30% decrease in cyclooxygenase-1 content. We hypothesize that the increase in renal TxB2 release after intestinal I/R could be secondary to an increased activity of thromboxane synthase. The decrease in renal PGE2 after intestinal I/R could be due to a decrease in cyclooxygenase-1 content, a decrease in cyclooxygenase activity, or a combination of both.
In summary, the present study supports the hypothesis that severe SMA I/R injury decreases renal function, which is associated with altered renal eicosanoid release. The rat kidney responded to severe splanchnic I/R injury by a relative increase in the ratio of the release of vasoconstrictor endogenous eicosanoids (TxA2) to the release of endogenous vasodilator renal eicosanoids (PGE2, PGI2), corresponding to a decrease in renal function. The prevention of these findings by Ptx, without reversal of the decrease in total renal artery blood flow, supports the hypothesis that Ptx exerted its protective effect on renal eicosanoid release and renal function at a microvascular level. The injury could be caused by leukocyte activation and adhesion with subsequent release of toxic substances such as oxygen-derived free radicals. The allopurinol experiments further support this hypothesis, suggesting that toxic oxygen metabolites contribute to the renal microvascular injury after severe intestinal I/R.
ACKNOWLEDGEMENTS
This study was supported by National Institute of General Medical Sciences Grants GM-38529 (S. I. Myers) and GM-38342 (S. I. Myers), Veterans Afffair Merit Grant (S. I. Myers), and American Heart Association Grant in Aid (R. H. Turnage).
FOOTNOTES
Address for reprint requests: S. I. Myers, Temple Univ. School of Medicine, Dept. of Surgery, Broad and Ontario Streets, 4th Floor-Parkinson Pavilion, Philadelphia, PA 19140.
Received 6 April 1995; accepted in final form 15 May 1997.
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