Phase I trial on the safety of topical rhVEGF on chronic neuropathic diabetic foot ulcers.

OBJECTIVE: To assess the safety/tolerability and perform a preliminary efficacy evaluation of a multiple-dosing regimen of recombinant human vascular endothelial growth factor (VEGF165 or rhVEGF; telbermin) applied topically to chronic diabetic neuropathic foot ulcers. METHOD: Subjects with type 1 or 2 diabetes mellitus were randomised to receive either topical applied telbermin (72 microg/cm2) (n=29) or placebo (n=26) treatment to the foot ulcer surface in conjunction with standard ulcer care. Subjects received treatment every 48 hours (maximum three doses per week) for up to six weeks. Weekly 35mm photography, quantitative planimetry and physical examinations documented the ulcer appearance, surface area and stage. Safety endpoints included incidence of clinically significant hypotension, adverse events and ulcer infection. Exploratory efficacy endpoints included percentage reduction in total ulcer surface area, incidence of complete ulcer healing and time to complete ulcer healing. RESULTS: Incidence of adverse events was comparable in the two treatment groups. None of the adverse events were attributed to study drug, and no hypotension was observed as a result of telbermin treatment. Occurrence of infected study ulcers appeared to be balanced between the treatment groups. Positive trends suggestive of potential signals of biological activity were observed for incidence of complete ulcer healing (41.4% telbermin versus 26.9% placebo at day 43 [P=0.39]) and time to complete ulcer healing (25th percentile of 32.5 days telbermin versus 43.0 days placebo [log-rank P=0.13]). CONCLUSION: The topical application of telbermin 72 microg/cm2 three times a week for up to six weeks appeared to be well tolerated. Further studies are required to characterise the safety/efficacy of telbermin more completely.

Nitric oxide enhances experimental wound healing in diabetes.

BACKGROUND: Diabetes is characterized by a nitric oxide deficiency at the wound site. This study investigated whether exogenous nitric oxide supplementation with the nitric oxide donor molsidomine (N-ethoxycarbomyl-3-morpholinyl-sidnonimine) could reverse the impaired healing in diabetes. METHODS: Wound healing was studied by creating a dorsal skin incision with subcutaneous polyvinyl alcohol sponge implantation in diabetic and non-diabetic rats. Half of each group was treated with molsidomine. Collagen metabolism was assessed by wound breaking strength, hydroxyproline (OHP) content, RNA expression for collagen type I and III, and matrix metalloproteinase (MMP) 2 activity in wound sponges. Wound fluid, plasma and urinary nitric oxide metabolite levels, and the number of inflammatory cells were assessed. RESULTS: OHP content and wound breaking strength were significantly increased by molsidomine. MMP-2 activity in wound fluid was decreased in diabetes and upregulated by nitric oxide donors. The impaired inflammatory reaction in diabetes was unaffected by nitric oxide donor treatment and ex vivo nitric oxide synthesis was no different between wound macrophages from control and diabetic animals, suggesting that the nitric oxide deficiency in the wound is due to a smaller inflammatory reaction in diabetes. CONCLUSION: The nitric oxide donor molsidomine can at least partially reverse impaired healing associated with diabetes.

Nitric oxide in the healing wound: a time-course study.

INTRODUCTION: We studied the time course of nitric oxide expression in the healing wound and the cell populations responsible for its synthesis. METHODS: Twenty four Lewis rats underwent subcutaneous implantation of polyvinyl alcohol sponges. Rats were sacrificed in groups of three on days 1, 3, 5, 7, 10, 14, and 35 after wounding. The conversion of 3H-labeled arginine to 3H-labeled citrulline, with or without N(G)-L-monomethyl-arginine (L-NMMA) in harvested sponges, was measured. Nitrate/nitrite (NOx) in plasma and wound fluid was quantified by Greiss reaction. Inducible nitric oxide synthase (iNOS) gene expression was determined by Northern analysis and reverse transcriptase-polymerase chain reaction (RT-PCR). Inducible NOS was identified in specific wound cell populations by dual-label flow cytometry. RESULTS: Nitric oxide synthase (NOS) activity peaked at 24 h after wounding (37.7 +/- 0.9 micromol citrulline per milligram sponge), with a steady decline thereafter. Percentage inhibition of NOS activity by l-NMMA was highest on days 1-7 (70-80%). This declined to 50% by day 10 and to 25% by days 14-35. The iNOS gene expression paralleled NOS biochemical activity. RT-PCR confirmed low-level expression up to 10 days after wounding. Plasma NOx levels remained within a narrow range of 22.6 +/- 1.3 to 29.3 +/- 1.5 microM throughout the postwounding period, while corresponding levels in wound fluid (microM) increased steadily from 27 +/- 3.8 on day 1 to 107.2 +/- 10.0 on day 14. Inducible NOS expression was detectable by fluorescence-activated cell sorting in wound macrophages on days 1 and 3 after wounding. CONCLUSIONS: Our findings suggest maximal NOS activity early in cutaneous wound healing, with sustained production up to 10 days after wounding. NOS biochemical activity was paralleled by iNOS gene expression. Plasma NOx remained constant, while wound fluid NOx increased steadily to peak at day 14. Wound macrophages appear to be a source of nitric oxide production in the early phase of wound healing.

Differential cytokine expression in skin graft healing in inducible nitric oxide synthase knockout mice.

Inducible nitric oxide synthase (iNOS) and its product, nitric oxide, have been shown to play important roles in wound biology. The present study was performed to investigate the role of iNOS in modulating the cytokine cascade during the complex process of skin graft wound healing.Fifteen iNOS-knockout mice and 15 wild-type C57BL/6J mice were subjected to autogenous 1-cm2 intrascapular full-thickness skin grafts. Three animals in each group were killed on postoperative days 3, 5, 7, 10, and 14. Specimens were then analyzed using nonisotopic in situ hybridization versus mRNA of tumor growth factor-beta1, vascular endothelial growth factor, iNOS, endothelial nitric oxide synthase (eNOS), tumor necrosis factor-alpha, and basic fibroblast growth factor, as well as positive and negative control probes. Positive cells in both grafts and wound beds were counted using a Leica microgrid. Scar thickness was measured with a Leica micrometer. Data were analyzed using the unpaired Student's t test. Expression of iNOS was 2- to 4-fold higher in knockout mice than in wild-type mice on postoperative days 5, 7, and 14. Expression of eNOS was 2- to 2.5-fold higher in knockout mice than in wild-type mice on postoperative days 5 and 7. Tumor necrosis factor-alpha expression was 2- to 7-fold higher in knockout mice than in wild-type mice on all postoperative days. In contrast, expression levels of angiogenic/fibrogenic cytokines (vascular endothelial growth factor, basis fibroblast growth factor, and tumor growth factor-beta1) were 2.5- to 4-fold higher in wild-type mice than in knockout mice. Scars were 1.5- to 2.5-fold thicker in knockout mice than in wild-type mice at all time points. All of the above results represent statistically significant differences (p < 0.05). Significantly different patterns of cytokine expression were seen in knockout and wild-type mice. Although the scar layer was thicker in knockout mice, it showed much greater infiltration with inflammatory cells. These data further delineate the modulatory effect of iNOS and nitric oxide in healing skin grafts.

The role of iNOS in wound healing.

BACKGROUND: We have previously shown that the blockade of nitric oxide (NO) synthesis impairs wound healing, in particular collagen synthesis. Conversely, impaired wound healing is accompanied by decreased wound NO synthesis. Fibroblast collagen synthesis, proliferation, and fibroblast-mediated matrix contraction are critical to wound healing. We examined the wound healing-related phenotypic changes that are induced by the loss of inducible nitric oxide synthase (iNOS) gene function in fibroblasts. METHODS: Dermal fibroblasts were obtained from 8- to 12-week-old iNOS--knock out (KO; C57BL/Ai-[KO] Nos2 N5) and wild type mice by an explant technique and used after 1 to 3 passages. Proliferation ([(3)H]-thymidine incorporation) and collagen synthesis ([(3)H]-proline incorporation into collagenase-sensitive protein) were studied after stimulation with 10% fetal bovine serum. Matrix remodeling was assessed by the measurement of the contraction of fibroblast-populated collagen lattices. RESULTS: iNOS-KO fibroblasts proliferated more slowly, synthesized less collagen, and contracted fibroblast-populated collagen lattices more slowly than wild-type fibroblast. Collagen synthesis was restored to normal in KO fibroblasts in response to NO donors (s-nitroso-N-acetylpenicillamine). CONCLUSIONS: iNOS deficiency causes significant impairment in wound healing-related properties of fibroblasts, which suggests that NO plays an important role in wound healing.

A novel method of studying wound healing.

In order to study wound healing, it is often necessary to administer various wound-active substances by the systemic route. It is unclear whether the observed effects are the result of local or systemic influence of the agent administered. Furthermore, high systemic doses are often required to achieve activity at the wound level. Direct intrawound administration of substances is traumatic and disruptive to the fragile wound environment and increases the risk of infection. We devised a system for continuous atraumatic delivery of substances directly to subcutaneously implanted polyvinyl alcohol sponges, an adaptation of a well-established model of wound healing. Sponge-catheter constructs were fashioned by feeding identical lengths of silicone catheters through two 40-mg sponge disks (on edge). The distal sponge was fixed 0.5 cm from the distal, ligated end of the catheter and centered over two 1-mm holes in the catheter tubing. The proximal sponge was fixed over nonperforated catheter with its edge 2 cm proximal from the close edge of the distal sponge. Each construct was connected to a mini-osmotic pump (infusion rate 1 microl/h) loaded with an appropriate infusate and inserted subcutaneously on the dorsum of anesthetized male Sprague-Dawley rats. Hydroxyproline (OHP) content of sponges, a measure of collagen deposition, was determined at 7 days postwounding. Infusion of India ink confirmed selective delivery to the distal sponge. Saline infusion alone significantly elevated OHP content compared to noninfused sponges (450 +/- 43 vs 328 +/- 36 microg OHP/100 mg sponge, P < 0.05). Infusion of S-methylisothiourea (a selective iNOS inhibitor, 84 microg/sponge/24 h) successfully inhibited NO production (35.9 +/- 3.1 vs 49.6 +/- 3.6 microM, P < 0.05) and decreased sponge OHP content (385 +/- 60 vs 568 +/- 70 microg OHP/100 mg sponge, P < 0.05) without the toxic side effect (i.e., weight loss) seen with systemic administration. Infusion of an adenoviral solution containing mouse iNOS cDNA resulted in successful transduction of wound cells demonstrating the ability to deliver genes to a healing wound model. The data demonstrate that manipulation of wound physiology is possible by local delivery of low doses of wound-active compounds to the wound site. This promises to be a powerful tool for the study of both normal and impaired wound healing.

Effect of matrix metalloproteinase inhibition on colonic anastomotic healing in rats.

Wound strength depends on the balance between collagen synthesis and degradation; however, the role of collagen breakdown in wound healing is still not well understood. We investigated the role of matrix metalloproteinases in wound healing by using BE16627B, a matrix metalloproteinase inhibitor. Identical surgical procedures consisting of a colonic anastomosis (single-layer, inverted) and implantation of an osmotic pump in the back were performed in male Sprague-Dawley rats weighing 270 to 290 grams. The animals were randomly assigned to receive either BE16627B (n = 10) dissolved in dimethylsulfoxide and diluted with ethylene glycol at a dosage of 2.4 mg/rat/day for 3 days or the vehicle solution alone (n = 11). The solutions were administered through the surgically implanted osmotic pumps. The animals were killed 4 days after surgery, and the colonic bursting pressure (mm Hg) and hydroxyproline concentration (microg/mg wet tissue, index of collagen) were measured. The administration of BE16627B enhanced colonic anastomotic healing, as measured by the increase in the colonic bursting pressure (160 +/- 12 vs. 125 +/- 7 mm Hg; P < 0.05) and the increase in the soluble fraction of collagen (0.27 +/- 0.01 vs. 0.21 +/- 0.01 microg/mg wet tissue; P < 0.01) in the anastomosis. Histologic examination of the tissue revealed that the use of BE16627B resulted in the preservation of the multilayered colonic structure and increased the network of collagen between both ends of the colon in the thickening submucosal layer. These findings demonstrate that the inhibition of matrix metalloproteinase activity influences colonic anastomotic healing, indicating a potential mechanism for enhancing anastomotic healing.

Trauma and wound healing: role of the route of nutritional support.

Following severe trauma and surgical injury, nutritional support via the enteral route has been shown to lead to increased survival and decreased complications when compared to the parenteral route. We hypothesized that the route of nutrient delivery may affect cutaneous wound healing following severe traumatic insult. Forty-six Sprague Dawley rats underwent bilateral closed femoral fractures, central venous catheterization, gastrostomy placement and dorsal skin incision with placement of polyvinyl alcohol sponges into subcutaneous pockets. Identical nutritional infusates of 25% dextrose, 4.25% amino acids, and vitamins were given, half the animals receiving the infusion via the gastrostomy (ENT) and the other half via the venous catheter (TPN). Animals were sacrificed on post-operative days 5, 7, or 10. Wound breaking strength (WBS, g) and sponge granuloma hydroxyproline content (OHP- a measure of wound collagen deposition, microg/ 100mg sponge) were measured. There were no significant nutritional differences between the two feeding groups. On days 5 and 7, WBS was significantly higher in the ENT group (58.0 +/- 3.1 g vs 48.9 +/- 2.6 g, p < 0.05, and 123 +/- 19 g vs 87.6 +/- 4.2 g, p < 0.05 vs TPN respectively). Sponge OHP content on day 5 was significantly higher in the ENT group (101 +/- 3 vs 86.7+/-5.8 microg/100 sponge, p < 0.05). These data demonstrate that the enteral feeding route imparts a benefit to early post-traumatic wound healing s compared to parenteral feeding.

Effect of early postoperative feeding on the healing of colonic anastomoses in the presence of intra-abdominal sepsis in rats.

PURPOSE: Intra-abdominal infection is generally considered a major risk factor for dehiscence of primary colon anastomosis. To elucidate the indications for nutritional support during intra-abdominal sepsis, we investigated the healing of anastomoses in an animal model. METHODS: Twenty male Sprague-Dawley rats (280-320 g) underwent cecal ligation and single puncture. After 24 hours the perforated cecum was removed, and the left colon was transected and anastomosed in a single-layer inverted fashion. Animals were randomly assigned to receive both chow and water (early-fed group; n = 10) or water alone for the first 72 hours and chow thereafter (late-fed group; n = 10). Colon-bursting pressure was measured five days after the anastomosis, at which time the anastomosis was excised. RESULTS: The survival rate after cecal ligation and single puncture was 100 percent, and blood cultures were positive in 20 percent of animals five days after surgery. All data are expressed as means +/- standard error of the mean. Body weight increased more in the early-fed group than in the late-fed group (15.6+/-3 vs. -6.3+/-2.8 g; P < 0.001). Early feeding resulted in increased anastomotic bursting pressure (200+/-11 vs. 161+/-12 mmHg; P < 0.05) and total collagen concentration at the site of anastomosis (2.36+/-0.09 vs. 2.01+/-0.07 microg/mg wet tissue; P < 0.01) compared with the late-fed group. CONCLUSION: Early feeding has a positive effect on anastomotic healing in the presence of intraabdominal sepsis. The mechanism by which early feeding enhances the colonic anastomotic healing is unclear, although preservation of colonic collagen seems to play a significant role.

Supplemental dietary arginine enhances wound healing in normal but not inducible nitric oxide synthase knockout mice.

BACKGROUND: Although generation of nitric oxide (NO) from inducible nitric oxide synthase (iNOS) has been shown to be required for cutaneous wound healing, no differences have been noted in incisional healing between iNOS knockout (iNOS-KO) and wild type (WT) mice. Because supplemental dietary arginine enhances cutaneous healing in normal rodents and is the sole substrate for NO synthesis, we studied whether arginine can enhance cutaneous wound healing in iNOS-KO mice. METHODS: Twenty iNOS-KO and 20 WT mice, all on a C57BL/6 background, were divided into 4 groups of 10 animals each. Ten animals with each trait were randomized to receive either normal food and tap water or food and water each supplemented with 0.5% arginine (w/w). All animals underwent a 2.5-cm dorsal skin incision with implantation of four 20-mg polyvinyl alcohol sponges into subcutaneous pockets. On postoperative day 14 the animals were killed. The dorsal wound was harvested for breaking strength determination and the wound sponges were assayed for hydroxyproline content and total wound fluid nitrite/nitrate concentration. RESULTS: Dietary arginine supplementation enhanced both wound breaking strength and collagen deposition in WT but not iNOS-KO mice. Wound fluid nitrite/nitrate levels were higher in WT than iNOS-KO animals but were not significantly influenced by additional arginine. CONCLUSIONS: These data demonstrate that supplemental dietary arginine enhances wound healing in normal mice. The loss of a functional iNOS gene abrogates the beneficial effect of arginine in wound healing. This suggests that the metabolism of arginine via the NO pathway is one mechanism by which arginine enhances wound healing.

Acute abdomen with colonic necrosis induced by Kayexalate-sorbitol.

Colonic necrosis is an unusual complication after treatment of hyperkalemia with sodium polystyrene sulfonate (SPS, Kayexalate) in sorbitol. To increase awareness of this complication, we report a case of necrosis of the transverse colon in a patient given oral and rectal SPS-sorbitol for hyperkalemia. Colonic necrosis was manifested as an acute abdomen within 24 hours of initial administration. Prompt surgical resection of the necrotic transverse colon permitted rapid recovery of bowel function. Although SPS crystals are seen microscopically in the necrotic bowel, experimental evidence implicates the sorbitol component of the SPS-sorbitol in the pathogenesis of colonic necrosis. A high index of suspicion for the unusual complication of colonic necrosis after oral or rectal administration of SPS-sorbitol may allow prompt recognition and surgical cure.

Role of nitric oxide in wound healing.

Nitric oxide is a short-lived free radical, that is capable of multiple effects at the molecular, cellular, and physiologic levels. Over the past several years, nitric oxide has been proved to play an important role in the healing of various types of wounds. The present review examines some of the recently defined roles of nitric oxide in normal and pathologic healing.

Role of arginine in immunonutrition.

Arginine plays an important role in many physiologic and biologic processes beyond its role as a protein-incorporated amino acid. Dietary supplementation of arginine can enhance wound healing, regulate endocrine activity and potentiate immune activity. Under normal unstressed conditions the arginine requirement of adult humans is fulfilled by endogenous sources, however this is compromised during times of stress, especially in critical illness. These finding have led to use of arginine supplementation as part of an immune-enhancing dietary regimen to help combat the immune suppression seen in such patients. Though the results from studies examining the use of this type of immunonutrition in critically ill patients are far from definitive, they are promising that this mode of therapy may be of some advantage. A better understanding of the in vivo biology of arginine and its metabolism is necessary to truly define a benefit from arginine supplementation.

Enhancement of fibroblast collagen synthesis by nitric oxide.

Fibroblasts can be stimulated by cytokines to synthesize nitric oxide (NO, nitrogen monoxide), while wound-derived fibroblasts synthesize NO spontaneously. Since wound fibroblasts are phenotypically characterized by greater collagen synthesis when compared to fibroblasts derived from noninjured tissue, we hypothesized that there may be a correlation between wound-induced NO synthesis and enhanced collagen production. To study the role of NO on collagen metabolism, normal dermal fibroblasts were cultured in the presence or absence of the NO donor S-nitroso-N-acetyl-penicillamine (SNAP) and their collagen metabolism was studied on the transcriptional as well as translational level. Fibroblast collagen synthesis was enhanced by 74.3 +/- 18.2 and 87.5 +/- 28.2% in the presence of 100 and 400 microM SNAP, respectively. This effect was not due to increased collagen type I or type III gene transcription. Cellular proliferation measured by thymidine incorporation was significantly decreased in the presence of SNAP, indicating that the increased collagen production was due to a net increase of collagen synthesis by the cells. Investigation of the collagen breakdown pathway showed that neither collagenase gene expression nor collagenase protein expression was affected by SNAP. The results of this study demonstrate for the first time that NO enhances collagen synthesis, most likely at a posttranslational level.

Inhibition of tumor necrosis factor-alpha attenuates wound breaking strength in rats.

Exogenous administration of tumor necrosis factor-alpha has been shown to both enhance and attenuate cutaneous healing in a dose-dependent manner. We examined the effects of tumor necrosis factor inhibition in the healing wound by both systemic and local administration of tumor necrosis factor-binding protein. Male Balb/C mice underwent dorsal skin incision with subcutaneous implantation of 20 mg polyvinyl alcohol sponges (4 per animal). In Experiment I, one group (n = 20) received intraperitoneal injections of tumor necrosis factor-binding protein (3 mg/kg) at the time of wounding, while another group (n = 20) received saline. Four animals from each group were euthanized on days 1, 3, 5, 7, and 14 postwounding. In Experiment II, one group (n = 10) received an intraperitoneal injection of tumor necrosis factor-binding protein (3 mg/kg) at the time of wounding and every third day thereafter. Another group (n = 10) received an intraperitoneal injection of saline at the time of wounding and every third day thereafter. In Experiment III, one group received a single intraperitoneal injection of tumor necrosis factor-binding protein (3 mg/kg) at the time of wounding (n = 7), or on postwounding day 4 (n = 7), or day 7 (n = 7). Another group received saline injections at the time of wounding (n = 7), or on postwounding days 4 or 7 (n = 7, respectively). All animals in Experiments II and III were killed at postwounding day 14. Wound breaking strengths were assessed using a tensiometer. Wound fluid collected from the implanted sponges was assayed for tumor necrosis factor-alpha and tumor necrosis factor-binding protein levels using a biological assay and enzyme-linked immunosorbent assay, respectively. Collagen gene expression in sponge granulomata was assessed by Northern analysis. Collagen deposition in sponges was quantified by measuring hydroxyproline content. Wounds were significantly weaker in the animals that received repeated injections of tumor necrosis factor-binding protein with a mean wound breaking strength of 93.1 g vs. 186.6 g in controls (p < 0.05). Wound breaking strength in groups that received a single injection of tumor necrosis factor-binding protein on either day 0, 4, or 7 postwounding were no different than their respective controls. There was no difference in the mean hydroxyproline content of sponges between any of the tumor necrosis factor-binding protein groups and their respective controls. Northern analysis for collagen I and III expression also revealed no differences. These data indicate that continued systemic administration of tumor necrosis factor-binding protein resulted in significantly weaker wounds with no corresponding differences in wound collagen content, and collagen gene expression. This suggests that tumor necrosis factor-alpha inhibition throughout healing leads to a qualitatively impaired wound without a quantitative alteration in collagen deposition.

Expression and function of inducible nitric oxide synthase during rat colon anastomotic healing.

Nitric oxide plays a significant but incompletely understood role in fibroblast function and cutaneous wound collagen synthesis; however, the participation of inducible nitric oxide synthase (iNOS) in gastrointestinal anastomotic healing has not been studied. Male Sprague-Dawley rats underwent single-layer left colonic anastomosis. Animals were killed at 24-hour intervals postoperatively and the anastomosis was excised. Parallel uninjured colon tissue samples were also analyzed. Reverse transcriptase-polymerase chain reaction confirmed the absence of iNOS messenger RNA in control colon and expression of the gene in anastomotic tissue on all study days. Northern hybridization demonstrated maximal iNOS messenger RNA transcription on day 1 with decreased levels on days 3 and 5. iNOS enzyme activity, measured biochemically by the conversion of [(3) H-arginine to [(3) H]-citrulline ex vivo, was also maximal on day 1 (7.35 +/- 1.34 pmol/mg protein/min [+/- standard error of the mean], n = 10) and decreased on days 3 (4.37 +/- 2.32 pmol/mg protein/min; n = 6) and 5 (2.80 +/- 0.92 pmol/mg protein/min; n = 6). Immunohistochemical staining demonstrated that (1) iNOS expression is confined to a discrete cell population in the region of the anastomosis containing inflammatory cells; (2) those cells assume a highly conserved position on the luminal edge of the proliferating scar; and (3) the iNOS-expressing cells are present throughout the fibroplastic phase of healing. To functionally assess the role of iNOS in colonic healing, rats were treated with a continuous intravenous infusion of S-methylisothiourea (a selective inhibitor of iNOS) at a dosage of 200 mg/kg/day for 5 days after anastomosis. There was a significantly reduced anastomotic bursting pressure in rats treated with the inhibitor as compared to rats treated with intravenous normal saline solution (108.4 +/- 13.2 mm Hg vs. 148.4 +/- 10.3 mm Hg; P <0.05). These results suggest that iNOS gene expression is induced during colonic anastomotic healing, that it is present through all phases of healing but is maximal through the inflammatory phase, and that iNOS activity is required for optimal anastomotic healing.

Effect of nutritional route on colonic anastomotic healing in the rat.

Although early enteral feeding has been shown to benefit cutaneous healing when compared to parenteral feeding, the effect of the route of nutritional support in gastrointestinal anastomotic healing has not been defined. The aim of the present study was to determine whether the route of nutritional support influences colonic anastomotic healing. Twenty male Sprague-Dawley rats weighing 270 to 290 grams underwent identical surgical manipulation consisting of central venous catheterization, gastrostomy insertion, and distal colonic anastomosis (single-layer, inverted). Identical nutrient infusates composed of 4.25% amino acids, 25% dextrose, and vitamins were administered, with half the animals receiving the infusions via the gastrostomy and the other half via the venous catheter. Animals were killed 5 days after surgery. There were no differences in nutritional parameters between the parenterally and enterally fed groups. Colonic anastomotic bursting pressure was significantly higher in the enterally fed group (180 +/- 6 vs. 150 +/- 11 mm Hg; P <0.01). The measured insoluble collagen and total protein content in anastomotic tissue were enhanced in the enterally supported group. The fraction of soluble (newly synthesized) collagen did not differ between the two groups. The data demonstrate that the route of nutrient administration influences colonic anastomotic healing. The preservation of colonic structural collagen in the enteral group may improve the ability of the gut to hold sutures and thus enhance anastomotic healing.

Arginine and nutrition in renal disease.

The physiological significance of arginine metabolism extends far beyond its incorporation as an amino acid into proteins. In addition to its effects when administered as a dietary supplement, the end-products of arginine metabolism by the enzymes arginase, arginine decarboxylase (ADC), and nitric oxide synthase (NOS) have been shown to play roles in wound healing, immune response, tumor biology, and the regulation of inflammation. These properties make arginine metabolism a significant concern in defining and, likely, treating renal disease.