TP6.1.4 Risk factors for post-cholecystectomy bile duct injuries: Systematic review and meta-analysis

Aims

Bile duct injury (BDI) is a major complication of cholecystectomy resulting in long-term consequences. The relatively low incidence (0.23% – 1.5%) of BDI makes the identification of risk factors challenging. The aim of this study was to systematically analyse available literature on BDI post-cholecystectomy to provide an update on the incidence and determine current risk factors.

Methods

The study was pre-registered on PROSPERO (CRD42020177318). A search was conducted of MEDLINE, EMBASE, Scopus, Cochrane Central, Web of Science databases and the grey literature from inception to February 2020. 1583 unique papers were identified and screened for eligibility. English language, retrospective and prospective studies were included where the population age was > 16 and underwent cholecystectomy.

Results

Outcomes analysed were incidence of BDI and risk estimates for possible risk factors. 30 studies (6,420,667 patients) were included in the meta-analysis. Gender, BMI>30, acute cholecystitis (AC), emergent surgery, the operative approach, intraoperative cholangiography (IOC) and the impact of surgeon’s experience were analysed. Male gender and AC were determined to be statistically significant risk factors (OR 1.25 (1.13-1.39)) and 1.74 (1.27-2.39) respectively). Furthermore, IOC use was found to be significantly associated with BDI risk (OR 1.27 (1.17 – 1.37), while BMI>30, open surgical approach, emergent surgery and surgeon’s experience were not statistically significant; however, significant heterogeneity among included studies limited the interpretation of these factors.

Conclusion

Male gender and AC were found to be predictors of BDI, while better quality evidence is needed to show the effect of other factors.

1163 Genome-wide Association Study Reveals 55 Loci Associated with Gallstone Disease

Aim

Gallstones have a prevalence of 20-40% in European populations and cause significant morbidity. Gallstones form from cholesterol and calcium bilirubinate and knowledge of genetic determinants remains incomplete. A genome-wide association study (GWAS) was performed to identify determinants of gallstones.

Method

A GWAS of 16,356,211 single nucleotide polymorphisms (SNPs) for 28,627 cases and 348,373 controls of European ancestry in the UK Biobank was undertaken. A logistic regression with additive allelic dosage was performed (significance: P < 5*10-8). Functional annotation and linkage disequilibrium clumping were performed to reveal distinct loci. Lead SNPs were investigated by linear regression for association with plasma lipids, liver enzymes and blood count markers.

Results

55 lithogenic loci were identified of which 27 are novel. Functional annotation revealed genes involved in metabolism of cholesterol, glucose, bile acids and bilirubin with corresponding changes in serum biomarkers caused by those lithogenic alleles. Several novel variants did not alter cholesterol or other biomarkers. Lithogenic variants within genes controlling intra- and paracellular transport may govern biliary composition (PCDHB4, NUP153, CLDN7) and promote lithogenic bile. Variants within genes which may influence gallbladder motility (ANO1, TMEM147) and cholangiocyte ciliogenesis (TBC1D32, ADAMTS20, DYNC2LI1, HNF1B) may promote gallstone formation through reduced biliary flow.

Conclusions

We identified 27 novel associations with gallstones. Impact of lithogenic alleles on serum biomarkers was highly variable demonstrating that gallstone formation is partially driven by pathways which do not influence cholesterol, glucose or bilirubin metabolism. Variants within genes that may influence biliary composition, bile flow and gallbladder motility represent new targets for research into gallstones.

O45: DEFINING CELL-ENRICHED MICRORNAS TO SUPPORT RATIONAL BIOMARKER SELECTION IN HUMAN RENAL TRANSPLANTATION

Introduction

MicroRNAs are promising biomarkers of renal disease, however the cellular origin of their expression is usually unclear limiting their interpretation when measured in renal biopsies and urine. We hypothesised that by first defining renal cell-enriched microRNAs, we could select biomarkers based on the expected histopathological profile.

Method

Small RNA-sequencing of cortical, proximal tubular (LTL), macrophage (F480), endothelial (CD31) and fibroblast (PDGFRb) populations from the reversible unilateral ureteric obstruction (rUUO) murine model was performed. Hierarchical clustering was used to identify clusters. Findings were translated into an ischaemia reperfusion injury (IRI) model and then into urine samples from renal transplant recipients (n=16) with delayed graft function (DGF) vs. those with primary function.

Result

Kidney injury resulted in significant macrophage infiltration and tubular injury which improved upon reversal. We characterised novel microRNA clusters enriched for each cell type. With injury there was a significant increase in macrophage (p<0.0001), fibroblast (p<0.01) and decrease in proximal tubule (p<0.0001) enriched microRNAs vs. non-enriched microRNAs. We validated macrophage enriched miR-18a, miR-16 and tubular enriched miR-194 in the IRI model, demonstrating that microRNA expression reflected the histological profile. In humans, urinary miR-16 (FC 16.9; p<0.05) and miR-18a (FC 10: p=0.06) were upregulated at day 2 in patients with DGF; outperforming the traditional injury marker KIM1.

Conclusion

This is the first study to characterise cell-enriched microRNAs during renal injury and repair. By defining the source of microRNA expression we were able to rationally select miR-16 and miR-18a as promising urinary biomarkers of renal injury.

Take-home message

We have found that microRNAs have differences in expression between cell types and renal injury states which is important when considering microRNA expression in samples composed of varying cellular composition. By defining the cellular origins of microRNA expression we were able to rationally select microRNA biomarkers of human renal injury.

Incidence and outcome of colorectal cancer in liver transplant recipients: A national, multicentre analysis on 8115 patients

BACKGROUND & AIMS

De novo malignancies after liver transplantation represent one of the leading causes of death in the long-term. It remains unclear whether liver transplant recipients have an increased risk of colorectal cancer and whether this negatively impacts on survival, particularly in those patients affected by primary sclerosing cholangitis and ulcerative colitis.

METHODS

In this national multicentre cohort retrospective study, the incidence of colorectal cancer in 8115 evaluable adult patients undergoing a liver transplantation between 1 January 1990 and 31 December 2010 was compared to the incidence in the general population through standardised incidence ratios.

RESULTS

Fifty-two (0.6%) cases of colorectal cancer were identified at a median of 5.6 years postliver transplantation, predominantly grade 2 (76.9%) and stage T3 (50%) at diagnosis. The incidence rate of colorectal cancer in the whole liver transplant population was similar to the general UK population (SIR: 0.92), but significantly higher (SIR: 7.0) in the group of patients affected by primary sclerosing cholangitis/ulcerative colitis. One-, five- and ten-year survival rates from colorectal cancer diagnosis were 71%, 48% and 31%, respectively, and the majority of colorectal cancer patients died of cancer-specific causes.

CONCLUSIONS

Liver transplantation alone is not associated with an increased risk of colorectal cancer development. The primary sclerosing cholangitis/ulcerative colitis liver transplant population showed a significantly higher risk of colorectal cancer development than the general population, with a high proportion of advanced stage at diagnosis and a reduced patient survival.

Impact of portal vein infiltration and type of venous reconstruction in surgery for borderline resectable pancreatic cancer

BACKGROUND

The International Study Group of Pancreatic Surgery (ISGPS) recommends operative exploration and resection of pancreatic cancers in the presence of reconstructable mesentericoportal axis involvement. However, there is no consensus on the ideal method of vascular reconstruction. The effect of depth of tumour invasion of the vessel wall on outcome is also unknown.

METHODS

This was a retrospective cohort study of pancreaticoduodenectomy with vein resection for T3 adenocarcinoma of the head of the pancreas across nine centres. Outcome measures were overall survival based on the impact of the depth of tumour infiltration of the vessel wall, and morbidity, in-hospital mortality and overall survival between types of venous reconstruction: primary closure, end-to-end anastomosis and interposition graft.

RESULTS

A total of 229 patients underwent portal vein resection; 129 (56·3 per cent) underwent primary closure, 64 (27·9 per cent) had an end-to-end anastomosis and 36 (15·7 per cent) an interposition graft. There was no difference in overall morbidity (26 (20·2 per cent), 14 (22 per cent) and 9 (25 per cent) respectively; P = 0·817) or in-hospital mortality (6 (4·7 per cent), 2 (3 per cent) and 2 (6 per cent); P = 0·826) between the three groups. One hundred and six patients (47·5 per cent) had histological evidence of vein involvement; 59 (26·5 per cent) had superficial invasion (tunica adventitia) and 47 (21·1 per cent) had deep invasion (tunica media or intima). Median survival was 18·8 months for patients who had primary closure, 27·6 months for those with an end-to-end anastomosis and 13·0 months among patients with an interposition graft. There was no significant difference in median survival between patients with superficial, deep or no histological vein involvement (20·8, 21·3 and 13·3 months respectively; P = 0·111). Venous tumour infiltration was not associated with decreased overall survival on multivariable analysis.

CONCLUSION

In this study, there was no difference in morbidity between the three modes of venous reconstruction, and overall survival was similar regardless of tumour infiltration of the vein.

Short-term outcomes after liver resection for malignant and benign disease in the age of ERAS

INTRODUCTION

Enhanced Recovery After Surgery protocols have been implemented effectively after liver resection and provide benefits in terms of general morbidity rates. In order to optimise peri-operative care protocols and minimise morbidity, further investigation is required to identify factors associated with poor outcome after liver resection.

METHODS

A retrospective analysis of patients undergoing liver resection and enhanced recovery care between January 2006 and September 2012 was conducted. Data were collected on patient outcome and demographics, operative and pathological details. Univariate and multivariate analyses were performed to determine independent predictors of adverse outcome.

RESULTS

603 patients underwent liver resection during the study period. Morbidity and mortality rates were 34.3% and 1.5% respectively. The only predictor of major morbidity was extended resection (OR 4.079; 95% CI 2.177-7.642).

CONCLUSIONS

Extended resection is associated with major morbidity. When determining optimum peri-operative care, ERAS protocols must incorporate care components that can mitigate against morbidity associated with extended resection.

Risk factors for recurrent primary sclerosing cholangitis after liver transplantation

BACKGROUND & AIMS

The association between primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD) is well recognised. However, the relationship between IBD and recurrent PSC (rPSC) is less well understood. We assessed the prevalence of rPSC and analysed the factors associated with rPSC post-liver transplantation and its influence on graft and patient survival.

METHODS

This is a UK multicentre observational cohort study across six of the seven national liver transplant units. All patients undergoing a first liver transplant for PSC between January 1 1990 and December 31 2010 were included. Prospectively collected liver transplant data was obtained from NHSBT and colitis data was retrospectively collected from individual units.

RESULTS

There were 679 (8.8%) first transplants for PSC. 347 patients (61.4%) had IBD, of which 306 (88.2%) had ulcerative colitis (UC). 81 (14.3%) patients developed rPSC and 37 (48.7%) of them developed graft failure from rPSC. Presence of UC post-liver transplant (HR=2.40, 95% CI 1.44-4.02) and younger age (HR=0.78, 95% CI 0.66-0.93) were the only factors significantly associated with rPSC. rPSC was associated with over a 4-fold increase in the risk of death (HR=4.71, 95% CI 3.39, 6.56) with 1, 5, and 10-year graft survival rates of 98%, 84%, and 56% respectively compared to 95%, 88%, and 72% in patients who did not develop rPSC.

CONCLUSION

The presence of UC post-liver transplant is associated with a significantly increased risk of rPSC. Furthermore, the presence of rPSC increases the rate of graft failure and death, with higher re-transplantation rates.

Outcome after pancreaticoduodenectomy for T3 adenocarcinoma: A multivariable analysis from the UK Vascular Resection for Pancreatic Cancer Study Group

BACKGROUND

Most resectable pancreatic cancers are classified as T3, including those involving the porto-mesenteric vein. Survival and perioperative morbidity for venous resection have been found to be comparable to standard resection. We investigate factors associated with short and long term outcomes in pancreaticoduodenectomy with (PDVR) and without (PD) venous resection exclusively for T3 adenocarcinoma of the head of the pancreas.

METHODS

This is a UK multicenter retrospective cohort study assessing outcomes in patients undergoing PD and PDVR. All consecutive patients with T3 only adenocarcinoma of the head of the pancreas undergoing surgery between December 1998 and June 2011 were included. Multivariable logistic and proportional hazards regression analyses were performed to determine the association between the surgical groups and in-hospital mortality (IHM) and overall survival (OS).

RESULTS

1070 patients were included of whom 840 (78.5%) had PD and 230 (21.5%) had PDVR. Factors independently associated with IHM were a high creatinine (aHR 1.14, p = 0.02), post-operative bleeding (aHR 2.86, p = 0.04) and a re-laparotomy (aHR 8.42, p = 0.0001). For OS, multivariable analyses identified R1 resection margin status (aHR 1.22, p = 0.01), N1 nodal status (aHR 1.92, p = 0.0001), perineural invasion (aHR 1.37, p = 0.002), tumour size >20mm (aHR 0.63, p = 0.0001) and a relaparotomy (aHR 1.84, p = 0.0001) to be independently associated with overall mortality.

CONCLUSION

This study on T3 adenocarcinoma of the head of the pancreas suggests that IHM is strongly associated with perioperative complications whilst OS is affected by histological parameters. Detailed pre-operative disease evaluation and advances in oncological treatment have the potential to improve OS.

Effect of analgesic modality on outcome following open liver surgery: a systematic review of postoperative analgesia

Postoperative analgesia following liver resection remains controversial. The traditional standard of care of thoracic epidural is increasingly questioned due to perceived associated complications and delays to recovery. Evidence supporting alternative analgesic techniques is emerging however best practice is not yet established. This review aimed to evaluate the literature to assess the optimum analgesic technique following liver resection. A systematic review was conducted of trials evaluating analgesic methods in open liver surgery. Primary outcome was the postoperative complication rate. Secondary outcomes were length of stay and pain scores. Fourteen trials matching the inclusion criteria were analysed. No difference was observed in systemic complication rates between analgesic modalities. Epidural was associated with prolonged length of stay when compared with continuous wound infiltration and intrathecal morphine. Epidural offered equivalent or superior pain scores when compared to alternative techniques. In summary current evidence suggests alternative analgesic modalities may provide favorable recovery outcomes following liver surgery but consistent evidence is limited. Epidurals provide superior pain relief to alternatives but this does not translate into reduced length of stay or complication rate following liver surgery.

Analgesia after open abdominal surgery in the setting of enhanced recovery surgery: a systematic review and meta-analysis

IMPORTANCE

The optimal analgesic technique following open abdominal surgery within an enhanced recovery protocol remains controversial. Thoracic epidural is often recommended; however, its role is increasingly being challenged and alternative techniques are being suggested as suitable replacements.

OBJECTIVE

To determine by meta-analysis whether epidurals are superior to alternative analgesic techniques following open abdominal surgery within an enhanced recovery setting in terms of postoperative morbidity and other markers of recovery.

DATA SOURCES

A literature search was performed of EMBASE, Medline, PubMed, and the Cochrane databases from 1966 through May 2013.

STUDY SELECTION

All randomized clinical trials comparing epidurals with an alternative analgesic technique following open abdominal surgery within an enhanced recovery protocol were included.

DATA EXTRACTION AND SYNTHESIS

All studies were assessed by 2 independent reviewers. Study quality was assessed using the Cochrane bias assessment tool and the Jadad and Chalmers modified bias risk assessment tools. Dichotomous data were analyzed by random or fixed-effects odds ratios. Qualitative analysis was performed where appropriate.

RESULTS

Seven trials with a total of 378 patients were identified. No significant difference in complication rate was detected between epidurals and alternative analgesic methods (odds ratio, 1.14; 95% CI, 0.49-2.64; P = .76). Subgroup analysis showed fewer complications in the patient-controlled analgesia group compared with epidural analgesia (odds ratio, 1.97; 95% CI, 1.10-3.53; P = .02). Following qualitative assessment, epidural analgesia was associated with faster return of gut function and reduced pain scores; however, no difference was observed in length of stay.

CONCLUSIONS AND RELEVANCE

Epidurals may be associated with superior pain control but this does not translate into improved recovery or reduced morbidity when compared with alternative analgesic techniques when used within an enhanced recovery protocol.

A role for helminth parasites in achieving immunological tolerance in transplantation

BACKGROUND

Helminths infect more than a quarter of the world's population. Their success as parasites is the result of active immunomodulation of the host immune response, which can have benefits for the host, particularly in suppressing harmful allergic and autoimmune responses. Accordingly, we tested the hypothesis that helminth infection reduces the immune response to allograft transplantation.

METHODS

C57BL/6 mice were implanted with a subcutaneous minipump that delivered a continuous infusion of secreted products from the model mouse intestinal parasite, Heligmosomoides polygyrus (equivalent to 7 μg of protein per day). Simultaneously, fully allogeneic skin grafts from BALB/c donors were performed. 7 days later, lymphocytes were isolated from allograft draining lymph nodes and analysed by flow cytometry.

FINDINGS

Flow cytometric analysis showed a 41·7% increase in the mean percentage of CD4+CD25+Foxp3+ regulatory T cells (of total CD4 cells) from a baseline of 8·1% (95% CI 7·4-8·8) in untreated mice to 11·5% (8·8-14·2) in the treatment group (p=0·0085). Treatment with parasite products also increased mean expression of the regulatory cell surface receptor PD1 by 62·2% in the effector CD4 T-cell population from a baseline of 7·7% (5·7-9·6) to 12·5% (7·5-17·4) (p=0·03).

INTERPRETATION

The results show that helminth-derived products can powerfully induce regulatory immunological mechanisms in the presence of a fully allogeneic transplant. Identification of the specific mechanisms involved in suppression of allograft rejection by helminth parasites could lead towards development of safe and effective novel therapeutic strategies.

FUNDING

Wellcome Trust.

Portal vein resection in borderline resectable pancreatic cancer: a United Kingdom multicenter study

BACKGROUND

Until recently, in the United Kingdom, borderline resectable pancreatic cancer with invasion into the portomesenteric veins often resulted in surgical bypass because of the presumed high risk for complications and the uncertainty of a survival benefit associated with a vascular resection. Portomesenteric vein resection has therefore remained controversial. We present the second largest published cohort of patients undergoing portal vein resection for borderline resectable (T3) adenocarcinoma of the head of the pancreas.

STUDY DESIGN

This is a UK multicenter retrospective cohort study comparing pancreaticoduodenectomy with vein resection (PDVR), standard pancreaticoduodenectomy (PD), and surgical bypass (SB). Nine high-volume UK centers contributed. All consecutive patients with T3 (stage IIA to III) adenocarcinoma of the head of the pancreas undergoing surgery between December 1998 and June 2011 were included. The primary outcomes measures are overall survival and in-hospital mortality. Secondary outcomes measure is operative morbidity.

RESULTS

One thousand five hundred and eighty-eight patients underwent surgery for borderline resectable pancreatic cancer; 840 PD, 230 PDVR, and 518 SB. Of 230 PDVR patients, 129 had primary closure (56%), 65 had end to end anastomosis (28%), and 36 had interposition grafts (16%). Both resection groups had greater complication rates than the bypass group, but with no difference between PD and PDVR. In-hospital mortality was similar across all 3 surgical groups. Median survival was 18 months for PD, 18.2 months for PDVR, and 8 months for SB (p = 0.0001).

CONCLUSIONS

This study, the second largest to date on borderline resectable pancreatic cancer, demonstrates no significant difference in perioperative mortality in the 3 groups and a similar overall survival between PD and PDVR; significantly better compared with SB.

In situ transverse rectus abdominis myocutaneous flap: a rat model of myocutaneous ischemia reperfusion injury

Free tissue transfer is the gold standard of reconstructive surgery to repair complex defects not amenable to local options or those requiring composite tissue. Ischemia reperfusion injury (IRI) is a known cause of partial free flap failure and has no effective treatment. Establishing a laboratory model of this injury can prove costly both financially as larger mammals are conventionally used and in the expertise required by the technical difficulty of these procedures typically requires employing an experienced microsurgeon. This publication and video demonstrate the effective use of a model of IRI in rats which does not require microsurgical expertise. This procedure is an in situ model of a transverse abdominis myocutaneous (TRAM) flap where atraumatic clamps are utilized to reproduce the ischemia-reperfusion injury associated with this surgery. A laser Doppler Imaging (LDI) scanner is employed to assess flap perfusion and the image processing software, Image J to assess percentage area skin survival as a primary outcome measure of injury.

Host cytokine genotype is related to adverse prognosis and systemic inflammation in gastro-oesophageal cancer

BACKGROUND

Systemic inflammation has been linked with reduced survival in cancer, however, the role of the host cytokine genotype versus tumour phenotype in the generation of this response is not clearly established. This study examined the relationship between cytokine polymorphisms (IL-1beta 511, IL-6 174, IL-10 1082, TNFalpha 308 and LTalpha +252) and serum cytokine concentrations, serum CRP concentration and survival duration in patients with gastro-oesophageal malignancy.

METHODS

Two hundred and three newly diagnosed patients with gastric or oesophageal cancer had serum CRP and cytokine concentrations determined by ELISA. SNP genotyping was performed by Taqman allelic discrimination genotyping and compared with the genotype observed in 266 healthy volunteers. Clinico-pathological information was collected prospectively and survival duration was recorded.

RESULTS

Distribution of the cytokine genotypes was similar between patients and controls. The IL-6 174 CC and IL-10 1082 GG genotypes were associated with elevated serum CRP (P = .03, P = .01, respectively; Mann-Whitney U test) and sTNF-R (P = .015, P = .02) concentrations. These genotypes were also associated with reduced survival duration (P = .01, P = .047; log-rank test). TNFalpha AA genotype was also associated with reduced survival duration on univariate (P = .032) and multivariate analysis (P = .006, multivariate model), but not with inflammatory markers. No other cytokine polymorphisms were associated with systemic inflammatory markers or prognosis.

CONCLUSIONS

There is a pro-inflammatory cytokine haplotype (IL-6 CC, IL-10 GG, TNFalpha AA) that is associated with adverse prognosis that may act, at least in part, through an inflammatory mediated mechanism. Determining patients' cytokine haplotype may improve prognostication and allow stratification for intervention studies.

Serum parathyroid hormone-related peptide is associated with systemic inflammation and adverse prognosis in gastroesophageal carcinoma

BACKGROUND

Parathyroid hormone-related peptide (PTHrP) is a tumor-derived circulating factor that has been associated with hypercalcemia of malignancy. The role of PTHrP as a prognostic indicator remains unclear. Studies suggest that it may function as a growth factor; and, recently, the ability of PTHrP to induce cytokine expression has been described. PTHrP also has been proposed as a procachectic factor. In this study, the authors investigated the prognostic value of PTHrP in patients who had gastroesophageal carcinoma without hypercalcemia and determined whether PTHrP was associated with systemic inflammation and adverse nutritional status.

METHODS

Patients were recruited at the time of diagnosis. Serum was collected for determination of c-terminal fragment PTHrP (cPTHrP) levels (by radioimmunoassay) and calcium levels as well as levels of serum cytokines and acute-phase proteins (with an enzyme-linked immunosorbent assay). Nutritional assessment of patients was undertaken at the same time as serum collection. Patients underwent routine staging, and survival duration was recorded.

RESULTS

One hundred fifty-one patients with esophagogastric carcinoma were recruited. Six of 151 patients (4.0%) patients were hypercalcemic, and 26 patients (17.2%) had elevated serum cPTHrP levels. There was no association between the cPTHrP level and either serum calcium concentrations (P = 0.72) or adverse nutritional status. Elevated cPTHrP, however, was associated with significantly higher serum levels of soluble tumor necrosis factor receptor (P = 0.008) and with significantly lower levels of transferrin (P = 0.009) and albumin (P = 0.02). There was also a weak association with C-related protein levels (P = 0.06). Elevated cPTHrP levels also were associated with an adverse prognosis, as determined by reduced survival duration, on univariate analysis (P = 0.038), but not on multivariate analysis (P = 0.15).

CONCLUSIONS

Elevated serum cPTHrP levels were present in approximately 17% of patients with gastroesophageal carcinoma in the absence of hypercalcemia and was associated with markers of systemic inflammation and with an adverse prognosis.

Effect of copper on nitric oxide synthase and guanylyl cyclase activity in the rat isolated aorta

1. The potential role of copper (Cu2+) in modulating the activity of nitric oxide synthase (NOS) and guanylyl cyclase (GC) was investigated by use of diethyldithiocarbamic acid (DEDCA), a high affinity Cu2+ chelator. 2. DEDCA 100 microM inhibited sodium nitroprusside (SNP; 0.005-10 microM)-evoked relaxation of rat isolated aortic rings precontracted with 3 microM phenylephrine (PE). A lower concentration of DEDCA (10 microM) did not significantly attenuate SNP-evoked responses but did inhibit relaxation to the endothelium-dependent dilator, A23187 (0.01-10 microM). 3. The presence of 100 microM Cu2+, but not 100 microM Fe2+, alone enhanced A23187- and SNP-evoked relaxation of aortae precontracted with PE. 4. The inhibitory effect of DEDCA on SNP- and A23187-induced relaxation was reversed by equimolar concentrations of Cu2+ but not Fe2+, indicating that DEDCA does not act via removal of haem-iron from the NOS and GC complexes. 5. Superoxide dismutase (30 mu ml-1) was without effect on the inhibition of DEDCA relaxation induced by either SNP or A23187 in aortae precontracted with PE. 6. When assessed by radioimmunoassay, DEDCA inhibited SNP- and A23187-stimulated cyclic GMP formation with IC50 values of 0.5 microM and 50 microM, respectively. 7. These data demonstrate that Cu2+ plays a role in controlling NOS and GC activity in the rat aorta.