T-cell-independent and T-cell-dependent antibody responses in patients with chronic renal failure

Antibody responses against pneumococcal capsular antigens and tetanus toxoid were measured in 14 patients with chronic renal failure who were managed by continuous ambulatory peritoneal dialysis (CAPD) or haemodialysis (HD) and in eight healthy controls. IgG antipneumococcal responses were predominantly of the IgG2 and to a lesser extent IgG1 subclasses, while the IgG response against tetanus toxoid was largely IgG1 with smaller amounts of IgG4 and IgG3. The post-immunisation serum levels of IgG1 and IgM antibody against both antigens were significantly reduced in the uraemic patients compared with controls (P less than 0.05). All the uraemic patients had normal levels of IgG, IgA and IgM in the serum, but elevated levels of IgG3 prior to immunisation. The mechanisms responsible for the asymmetric depression of antibody responses in uraemia are unclear and may account in part for the increased susceptibility to infection in these patients.     

Effects of uraemia and dialysis modality on polymorphonuclear cell apoptosis and function.

BACKGROUND: Previous studies have reported that incubation of polymorphonuclear cells (PMN) in uraemic plasma or with different haemodialysis membranes and peritoneal dialysis solutions increases apoptosis in this cell type. In addition, PMN harvested from uraemic patients show a reduced ability to generate superoxide in response to stimuli as well as impaired phagocytosis, chemotaxis and degranulation. The aim of the current study was to investigate the effect of uraemia and dialysis modality on apoptosis and function in freshly harvested non-incubated PMN. METHODS: Polymorphonuclear cells were harvested from 14 chronic haemodialysis (HD) patients, from 14 continuous peritoneal dialysis patients (CAPD), 28 chronic kidney disease (CKD), pre-dialysis patients and from 14 healthy subjects (Controls). In these in vivo experiments, PMN apoptosis was studied by means of flow cytometric analysis of annexin V binding to freshly isolated cells. Polymorphonuclear cell phagocytosis and production of reactive oxygen species by unstimulated or stimulated (S.aureus, fMLP, PMA) cells were also studied by flow cytometry using whole blood. RESULTS: We observed increased PMN apoptosis in CKD patients. CAPD and HD patients displayed PMN apoptosis rates similar to controls. In the HD group, PMN exhibited decreased phagocytosis rates. In contrast, phagocytosis rates in PMN from CAPD were not significantly different from controls. In the CKD and HD groups, apoptosis was inversely correlated with respiratory burst activity and phagocytosis. CONCLUSION: Our results suggest that both uraemia and treatment modality may interfere with PMN apoptosis and function. Dialysis appears to normalize the increased PMN apoptosis rates observed in CKD patients.     

Diffuse intermyocardiocytic fibrosis in uraemic patients

At post-mortem we examined heart tissue of (i) 31 patients with uraemia not on dialysis, (ii) 42 patients on haemodialysis for less than 6 months, (iii) 60 patients on haemodialysis for more than 6 months, (iv) 16 patients after renal transplantation, and (v) 11 patients on CAPD. Patients with stenosing coronary lesions were excluded. Diffuse non-coronary intermyocardiocytic fibrosis, assessed by a score system in trichrome-stained sections, was found in 91% of chronically uraemic patients, but not in non-hypertensive, non-diabetic controls. The lesion was present even in non-dialysed uraemic patients; in dialysed patients its severity was related to the duration of dialysis; it was demonstrable even years after renal transplantation. On electron-microscopy, collagen fibres were seen, while beta 2-M amyloid was consistently absent. Logistic regression analysis showed that uraemia was a determinant of intermyocardiocytic fibrosis independent of hypertension, diabetes mellitus, anaemia, heart weight, and presence or absence of dialysis procedure.     

Abnormal calcaemic response to PTH in the uraemic rat without secondary hyperparathyroidism

BACKGROUND: Skeletal resistance to the calcaemic action of parathyroid hormone(PTH) is an important pathogenic factor in the development ofsecondary hyperparathyroidism. Since parathyroidectomy normalizesthe calcaemic response to PTH in uraemic animals, the increasein PTH levels has been advanced as a cause of skeletal resistanceto the calcaemic action of PTH. This study was designed to evaluatein uraemic rats the effect of normal PTH levels on the calcaemicresponse to PTH. METHODS: To maintain normal PTH levels, rats were parathyroidectomized(PTX) and rat 1–34 PTH was infused at a rate of 0.022µg/100 g per hour via a subcutaneously implanted miniosmoticpump; this rate of infusion was considered to be the normalPTH replacement dose since it normalized serum calcium and phosphorusin PTX rats with normal renal function. Two separate studieswere performed. In the first study, rats were maintained ona moderate-phosphorus (0.6%) diet and rats were divided intofour groups: (I) normal; (II) uraemic; (III) PTX with normalPTH replacement; and (IV) uraemic with PTX and normal PTH replacement.In a second study, the groups were the same except that a high-phosphorus(1.2%) diet was given to increase the magnitude of hyperparathyroidismin rats with intact parathyroid glands; an additional group(V) identical to group IV except that rats received daily calcitriolwas included. After 14 days, rats received a 48-h infusion ofhigh-dose rat 1–34 PTH (0.11 µg/100 g per hour)to evaluate the calcaemic response to PTH. RESULTS: The calcaemic response to PTH was similar in normal rats andPTX rats with PTH replacement on both a moderate and high-phosphorusdiet. In uraemic rats, the calcaemic response to PTH was decreasedand the maintenance of normal PTH levels by PTH replacementdid not correct the decreased calcaemic response to PTH; moreover,calcitriol supplementation did not improve the calcaemic responseto PTH. Finally, hypocalcaemia was observed in uraemic ratswith PTH replacement and was more profound than in rats on ahigh-phosphorus diet. CONCLUSIONS: This study demonstrates that the maintenance of a normal PTHlevel in uraemic rats did not correct the impaired calcaemicresponse to PTH, suggesting that factors intrinsic to uraemia,independent of phosphorus, calcitriol, and PTH participate inthe decreased calcaemic response to PTH in uraemia.     

Multi-Centre Study on Outcome of Treatment in Patients on Continuous Ambulatory Peritoneal Dialysis and Haemodialysis

In a multi-centre study by seven large renal units in the UnitedKingdom, the morbidity and mortality of all patients startingCAPD and haemodialysis during a 2-year period (1983–1984)has been monitored prospectively and related to reasons forchoice of therapy and potential risk factors. Over this period 338 new patients (mean age 48; range 3–77years) started CAPD; 17% had diabetes mellitus and 25% had cerebro/cardiovasculardisease. One hundred and seventy-five patients (mean age 45;range 5–73 years) started haemodialysis; 6% had diabetesmellitus and 14% had cerebro/cardiovascular disease. The Kaplan-Meieractuarial patient survival estimates at 2 years were haemodialysis84% and CAPD 83%, whilst technique survival figures for thesame period were haemodialysis 92% and CAPD .80%. Cox's regressionanalysis showed that cerebro/cardiovascular disease and age>60 years were most important predictors for survival inCAPD patients, in whom smoking appeared to be a significantrisk factor, for permanent change of therapy to haemodialysis.The major cause of ‘drop out’ in both groups wastransplantation, whilst hospitalisation was 14.9 days per patientyear for CAPD and 12.8 for haemodialysis patients. Within theCAPD group a temporary change to haemodialysis (<2 months)occurred on 106 occasions (each of mean of 19 days duration),amounting to 10 days per patient year of therapy. CAPD was used twice as often as haemodialysis for managing newpatients. After 2 years hospitalisation technique and patientsurvival were comparable in the two groups, with cerebro/cardiovasculardisease, age, and smoking being significant predictors of outcome.     

Enhanced Gastrointestinal Absorption of Aluminium in Uraemia: Time Course and Effect of Vitamin D

The present study examines the time course of aluminium absorptionin uraemic rats vs controls and investigates the effect of vitaminD. Following an oral load of 410 µmol aluminium there wasa significant increase in the urinary excretion rate of aluminiumas early as 60 min in uraemic rats. Compared with controls thisincrease was significantly greater in uraemic animals and maximumexcretion rates (77±49 vs pre-load 2±1 nmol Al/h)were achieved after 2 h. When vitamin-D-deficient rats with normal renal function werecompared with vitamin-D-replete controls, the latter excreteda significantly greater amount of the oral dose of aluminiumin their urine (727±361 vs 359±l40nmol Al/5d;P<0.02) and the post-load increase in the serum aluminiumconcentration was more pronounced in the vitamin-D-replete animals. Aluminium administered i.v. resulted in similar urinary aluminiumexcretion rates in both groups. In uraemicrats, however, regardlessof their vitamin D status, adminis tration of 1,25(OH)₂D₃ hadno effect on the amount of urinary aluminium excretion afteroral or i.v. loads. These findings suggest that although in rats with normal renalfunction aluminium absorption appears to be partly vitamin Ddependent, 1,25(OH)₂D₃ does not further augment the enhancedgastrointestinal absorption of aluminium in uraemia.     

Serum concentrations and peritoneal loss of growth hormone and growth-hormone-binding protein activity in older adults undergoing continuous ambulatory peritoneal dialysis: comparison with haemodialysis patients and normal subjects

Serum concentrations and peritoneal losses of growth hormone(GH) and of growth-hormone-binding protein (GH-BP) activityin 13 patients undergoing continuous ambulatory peritoneal dialysis(CAPD) were compared with those of 13 patients on haemodialysisand 13 normal subjects. The individuals in the three groupswere matched by age (40–83 years), gender, and serum glucoseconcentration. In addition CAPD and haemodialysis patients werematched by haematocrit, serum creatinine and albumin concentrations,and period of time on dialysis (0.5–127 months). GH inthe serum and in the peritoneal effluent were measured by radioimmunoassay(RIA) and NB2 bioas-say. GH-BP activity was analysed by bindingassay and expressed as a percentage of the specific bindingof GH. In the haemodialysis patients, serum GH was significantlygreater and serum GH-BP activity significantly less than inthe CAPD patients and control subjects. Between the two lattergroups no significant differences in GH or in GH-BP activitywere observed. GH bioactive/immunoactive ratios in the threegroups were similar. Both GH and GH-BP were detected in theperitoneal effluent of CAPD patients, in whom an overnight (8-h)peritoneal loss of GH (8.0±1.4x 10^–3 ug/h/1.73m2) was strongly correlated with serum GH (r= 0.840). CirculatingGH and GH-BP activity were influenced by serum creatinine andhaematocrit. In addition a positive relationship was observedbetween GH-BP activity and body mass index and between GH andtime on dialysis. These data reaffirm that older adults undergoinghaemodialysis, unlike CAPD patients, exhibit persistent abnormalitiesin GH-GH-BP axis. The peritoneal losses of GH and GH-BP thatoccur during CAPD do not affect their respective serum concentrations.     

Impact of dialysis therapy on insulin resistance in end-stage renal disease: comparison of haemodialysis and continuous ambulatory peritoneal dialysis.

BACKGROUND: Insulin resistance contributes to the pathogenesis of atherosclerotic cardiovascular disease and, thus, has an important impact on the mortality of uraemic patients. Haemodialysis (HD) is known to improve insulin resistance observed in uraemia. However, it is not known whether continuous ambulatory peritoneal dialysis (CAPD) alleviates insulin resistance in adult uraemic patients. The objective of this study was to compare the effect of two different dialysis modalities, HD and CAPD, on insulin resistance in adult uraemic patients and to identify the possible predictive factors for changes in insulin resistance. METHODS: Insulin resistance was examined in 19 non-diabetic patients with end-stage renal disease (ESRD) before and after dialysis therapy (HD, n=10; CAPD, n=9), as well as in 10 healthy controls using the hyperinsulinaemic euglycaemic glucose clamp technique. The glucose disposal rate (GDR mg/kg/min) was used as an index of insulin sensitivity during the clamp technique. We also determined which of various biochemical parameters might be associated with change in insulin resistance by carrying out multiple logistic regression analysis. RESULTS: GDR was significantly lower (6.44+/-1.76) in ESRD subjects than in normal subjects (9.90+/-2.01). HD and CAPD therapies significantly normalized GDR from 6.53+/-1.84 to 9.74+/-2.88 and from 6.35+/-1.65 to 8.18+/-1.76 respectively. Multiple logistic regression analysis showed that changes in BUN, haematocrit and plasma bicarbonate were significant predictive factors for the change in insulin resistance. CONCLUSION: CAPD therapy, in spite of its possible adverse effects in patients with atherosclerotic disease, has been shown to improve insulin resistance in adult uraemic patients, similarly to HD therapy.     

Uraemic pruritus and exposure to di(2-ethylhexyl)phthalate (DEHP) in haemodialysis patients

Uraemic pruritus is a frequent and disabling symptom in patientson dialysis. The pathogenesis of uraemic pruritus is neverthelessstill obscure. We investigated whether di (2-ethylhexyl ) phthalate(DEHP), the most commonly used plasticizer in polyvinyichloride(PVC) haemodialysis tubings, is a possible pathogenetic factorin uraemic pruritus. Serum concentrations of DEHP and its majorderivatives mono-(2-ethylhexyl ) phthalate (MEHP), 2-ethylhexanol(2-EH) and phthalic acid (PA) were determined in uraemic patientsbefore and after a haemodialysis session and compared with theoccurrence and intensity of pruritus in these patients. Twenty-onepatients on regular haemodialysis for at least 6 months wereexamined. The severity of uraemic pruritus was assessed usinga standard questionnaire (pruritus score). The quantitativeanalysis of DEHP and its derivatives was carried out by GC/selectedion monitoring mass spectrometry. Fourteen out of 21 patients(66%) complained about uraemic pruritus to a variable degree.The post-dialysis serum concentrations of DEHP, MEHP and 2-EHwere significantly higher than the corresponding pre-dialysisvalues, whereas the post-dialysis concentrations of PA (0.122±0.078µg/ml) were significantly lower than pre-dialysis levels(0.194±0.101 µg/ml, P=0.00068). Neither pre- norpost-dialysis serum concentrations of DEHP, MEHP, PA or 2-EHwere correlated with the severity of uraemic pruritus. Additionally,serum concentrations of DEHP and its metabolites did not differsignificantly in patients with and without pruritus. These findingssuggest that patients on haemodialysis are regularly exposedto considerable amounts of DEHP and metabolites. Phthalic acid,one of the presumed end products of DEHP metabolism, might beeliminated at least in part by haemodialysis. The expositionto DEHP and metabolites during haemodialysis, as assessed bymeasuring serum concentrations, bears no immediate realtionto the occurence or intensity of uraemic pruritus.     

Tryptophan and its metabolites in patients on continuous ambulatory peritoneal dialysis and following renal transplantation

Plasma tryptophan (Trp) concentration in its total (TTrp) andnon-protein-bound free form (FTrp) and its metabolite 5-hydroxyindole-3-aceticacid (5-HIAA) as well as muscle Trp contents (MTrp) were studiedin 12 uraemic patients undergoing continuous ambulatory peritonealdialysis (CAPD), 10 renal transplant patients, and 10 healthycontrol subjects. The CAPD patients exhibited signs of muscleweakness, as assessed by dynamometry, and signs of protein malnutritionwith a decreased ratio of alkalisoluble protein relative toDNA in muscle as well as low serum albumin concentration. Inthe uraemic patients TTrp was markedly reduced, whereas in thetransplant patients it did not differ from the controls. TheFTrp, which was separated by the process of equilibrium dialysis,was less in the uraemic (P<0.01) as well as transplant patients(P<0.0l) than in the controls. The plasma FTrp/TTrp ratiowas increased in the uraemic patients (40±8%) but lessin the transplant patients (16±4%), as compared to thecontrols (25±5%). The uraemic patients had increasedplasma concentrations of 5-HIAA, whereas this metabolite couldnot be found in the plasma of renal transplant patients andhealthy controls. MTrp was increased by an average of 33% inthe uraemic patients whereas it did not differ between the transplantpatients and the controls. The results indicate that the abnormalTrp metabolism in uraemic patients is to a large extentcorrectedby a successful renal transplantation. The increased MTrp inCAPD patients would suggest thatthe marked reduction in theplasma Trp, TTrp, and FTrp reflects a shift from the extra-to the intracellularspace rather than a depletion of Trp.     

The imbalance in the ratio of Th1 and Th2 helper lymphocytes in uraemia is mediated by an increased apoptosis of Th1 subset.

BACKGROUND: In uraemia there is a reduction in the total number of T lymphocytes and an imbalance in the ratio of Th1/Th2 T-helper (Th) lymphocytes. A higher rate of apoptosis in T lymphocytes has been reported in haemodialysis patients. The aims of the present study were to assess the Th1/Th2 pattern in uraemia and to evaluate whether a relative increase in Th1 apoptosis may explain the Th1/Th2 imbalance observed in uraemic patients. METHODS: Seventeen non-dialysed uraemic patients were evaluated; eight healthy volunteers served as controls. Intracellular interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) were measured by direct intracellular immunofluorescence and flow cytometry. Apoptosis was determined by flow cytometry using annexin V or TUNEL. Mechanisms of apoptosis were assessed by determination of Fas and Bcl-2 expression. RESULTS: Cell production of cytokines is significantly higher in uraemic patients than in controls. In addition, in uraemic patients only 5.1+/-2.1% of the T lymphocytes contained IFN-gamma (Th1 cells) while 61.9 +/- 14.8% contained IL-4 (Th2 cells) (P < 0.0001). The percentage of apoptosis was 29.6 +/- 6.3% and 4.7 +/- 1.6% in Th1 and Th2 lymphocytes, respectively (P < 0.001). Fas expression was higher in Th1 than in Th2 cells and the expression of Bcl-2 was lower in Th1 than in Th2 cells. The apoptosis induced by anti-Fas antibodies was similar in both types of lymphocytes. CONCLUSIONS: In uraemia there is a reduction in the proportion of Th1 lymphocytes due to a higher rate of apoptosis in this subset of lymphocytes. Th1 from uraemic patients show a higher expression of Fas and a lower expression of Bcl-2 than Th2. This makes uraemic Th1 cells more susceptible to apoptosis. The Th1/Th2 imbalance may contribute to alterations in cellular immunity observed in chronic kidney disease patients.     

Effects of haemodialysis and continuous ambulatory peritoneal dialysis on the plasma clearance of an albumin-bound furan dicarboxylic acid

Organic acids that are strongly bound to albumin are not removedby dialysis and the plasma concentrations of one such substance,a furan dicarboxylic acid (3-carboxy-4-methyl-5-propyl-2-furan-propanoicacid; 5-propyl FPA) have been measured by HPLC in healthy subjects(n=21), patients on regular haemodialysis (n=30), and patientstreated by continuous ambulatory peritoneal dialysis (n=21).The mean (±SD) concentrations of 5-propyl FPA were significantlyhigher in haemodialysis (95±44 µM) compared toCAPD patients (28±19 µM)) and both were higherthan in healthy individuals (14±7 µM). Haemoglobinconcentrations in CAPD patients were significantly higher thanin those on haemodialysis while these patients had significantlyhigher albumin concentrations than CAPD patients. The concentrationof 5-propyl FPA was positively correlated with the durationof dialysis for haemodialysis patients but not for CAPD patients.The lower concentrations of 5-propyl FPA in CAPD patients mayat least partly explain the higher haemoglobin levels foundin these patients.     

Concentration of dimethyl-L-arginine in the plasma of patients with end-stage renal failure

Abstract. N^GN^Gdimethyl-L-arginine (asymmetric dimethyl-L-arginineADMA) and N^GN^G dimethyl-L-arginine (symmetric dimethyl-L-arginine;SDMA) are naturally occurring analogues of L-arginine, the substratefor nitric oxide (NO) synthesis. ADMA is a potent inhibitorof NO synthesis, and accumulates in the plasma of patients withrenal failure. However the precise concentration of ADMA andSDMA in renal patients is still controversial. This study wasperformed to measure plasma ADMA and SDMA concentrations bytwo different HPLC techniques in nine healthy controls and 10uraemic subjects, and to investigate the effects of haemodialysis.In controls, the mean (±SEM) plasma concentrations ofADMA and SDMA were 0.36±0.09 and 0.39±0.05 µmol/lrespectively, yielding an ADMA/SDMA ratio of 1.2± 0.17.In uraemic patients, the plasma concentrations of ADMA and SDMAwere 0.9±0.08 µmol/l (P<0.001 compared to controls)and 3.4±0.3 µmol/l (P<0.001 compared to controls)with an ADMA/SDMA ratio of 0.27±0.015 (P<0.001). Inthe course of one 4 h haemodialysis session, ADMA concentrationsdecreased from 0.99±0.13 to 0.77±0.3 µmol/land SDMA concentrations from 3.38±0.44 to 2.27±0.21µmol/l. The plasma ADMA/creatinine ratio tended to increasefrom 1.26±0.20 x 10^–3 to 2.01±0.41 x 10^–3It is concluded that there is a modest (3-fold) but definiteincrease in plasma ADMA concentration in uraemic patients comparedto controls. SDMA accumulates to a greater degree (8-fold increase)and more closely parallels creatinine concentration than ADMA.The change in the ADMA/SDMA ratio is not accounted for by greaterrenal or dialysis clearance of ADMA, and, even though alternativeexplanations are not excluded, greater metabolism of ADMA thanSDMA is the most likely explanation. Although small in magnitude,the increase in ADMA concentration might be biologically significant.     

Evoked potentials (VEPs and BAEPs) in a large cohort of short- and long-term haemodialysed patients

To evaluate the presence and the severity of uraemic encephalopathy(UE) in regular dialysis treatment patients in relation to dialyticage, pattern reversal visual evoked potentials (PRVEPs) andbrainstem auditory evoked potentials (BAEPs) were respectivelyperformed in 86 and 98 patients on haemodialysis for 1–194months, divided into three subgroups according to dialytic age(group 1, <5 years of regular dialysis; group 2, 5–10years; group 3, >10 years). VEPs in the whole group of 86 patients and in each subgroupwith different dialytic age differed significantly from controlsfor both eyes, 41.7% of whom had pathological P100; no differenceswere observed between the three subgroups. BAEPs were pathological in 9.7% of the ears and 18.4% of patients.On the right ear the three subgroups were significantly differentfrom controls in the latencies of peaks III and V; subgroup2 and 3 differed from controls in the I-V interpeak, while theinterpeak I-III was different from controls only in subgroup3. On the left ear the three subgroups differed significantlyfrom controls in the latencies of peak V; subgroup 2 and 3 weresignificantly different from controls in the latency of peakI; subgroup 3 was different in the peak III latency; subgroup1 and 3 were different from controls in the interpeak I-V; nodifferences were observed in BAEPs between the three subgroupswith increasing dialytic age. No significant correlations werefound between the neurophysiological parameters and some biochemicalparameters (urea, creatinine, PTH). In summary, regular dialysisdoes not prevent the persistence of mild signs of uraemic encephalopathy,but these signs do not appear to worsen with increasing dialyticage.     

Uraemic medium causes endothelial cell dysfunction characterized by an alteration of the properties of its subendothelial matrix

Uraemic patients suffer from haemorrhagic disorders and acceleratedatherosclerosis. To evaluate the possible role of the vesselwall in these haemostatic alterations associated with uraemia,we investigated the effect of a uraemic milieu on human endothelialcell (EC) cultures and the reactivity of the extracellular matrices(ECM) generated by these cells towards platelets. EC cultureswere exposed to a pool of sera (20% in the culture medium) obtainedeither from uraemic patients or from normal donors, and thefollowing parameters were evaluated: (1) EC viability (trypanblue exclusion test); (2) von Willebrand factor (vWF) levelsin supernatants and associated with ECM; (3) the reactivityof EC and EC-derived ECM towards platelets, measured ‘exvivo’ under flow conditions (5 min, wall shear rate 800s^–1); and (4) ultrastructure of the ECM. The viabilityof EC cultured in the presence of uraemic sera was similar tocontrols. Platelet interaction with ECM generated by EC exposedto uraemic sera was significantly reduced (P<0.05). Thisdecrease was mainly related to a reduction in platelet adhesion(9.8 ± 1.9% vs 16.7±1.8% in controls, P<0.02).VWF levels in supernatants and associated with ECM were similarto controls. Ultrastructural analysis of the ECM generated byEC exposed to uraemic sera revealed a deficient matrix. An increasedremoval of EC was observed in experiments in which EC culturedin the presence of uraemic sera were perfused with citratedblood. These results indicate that a uraemic milieu induces quantitativeand qualitative changes in the vascular subendothelium, characterizedby a less intrincate network of fibrils, as well as a decreasedattachment of EC and reduced thrombogenicity to the ECM. Thesechanges may represent another mechanism which contributes tothe haemostatic dysfunction observed in uraemic patients.     

Regulation of alpha-cell function by the beta-cell in isolated human and rat islets deprived of glucose: the "switch-off" hypothesis

The "switch-off" hypothesis to explain beta-cell regulation of alpha-cell function during hypoglycemia has not been assessed previously in isolated islets, largely because they characteristically do not respond to glucose deprivation by secreting glucagon. We examined this hypothesis using normal human and Wistar rat islets, as well as islets from streptozotocin (STZ)-administered beta-cell-deficient Wistar rats. As expected, islets perifused with glucose and 3-isobutryl-1-methylxanthine did not respond to glucose deprivation by increasing glucagon secretion. However, if normal rat islets were first perifused with 16.7 mmol/l glucose to increase endogenous insulin secretion, followed by discontinuation of the glucose perifusate, a glucagon response to glucose deprivation was observed (peak change within 10 min after switch off = 61 +/- 15 pg/ml [mean +/- SE], n = 6, P < 0.01). A glucagon response from normal human islets using the same experimental design was also observed. A glucagon response (peak change within 7 min after switch off = 31 +/- 1 pg/ml, n = 3, P < 0.01) was observed from beta-cell-depleted, STZ-induced diabetic rats whose islets still secreted small amounts of insulin. However, when these islets were first perifused with both exogenous insulin and 16.7 mmol/l glucose, followed by switching off both the insulin and glucose perifusate, a significantly larger (P < 0.05) glucagon response was observed (peak change within 7 min after switch off = 71 +/- 11 pg/ml, n = 4, P < 0.01). This response was not observed if the insulin perifusion was not switched off when the islets were deprived of glucose or when insulin was switched off without glucose deprivation. These data uniquely demonstrate that both normal, isolated islets and islets from STZ-administered rats can respond to glucose deprivation by releasing glucagon if they are first provided with increased endogenous or exogenous insulin. These results fully support the beta-cell switch-off hypothesis as a key mechanism for the alpha-cell response to hypoglycemia.     

Influence of first and long-term dialysis on uraemia-associated increased basal production of interleukin-1 and tumour necrosis factor alpha by circulating monocytes

In a previous study we demonstrated the presence of circulating interleukin-1 (IL-1) in long-term haemodialysis patients and of tumour necrosis factor alpha (TNF alpha) in both long-term haemodialysis and not-yet-dialysed uraemic patients. The present report investigates the spontaneous capacity of monocytes to produce and secrete these two cytokines in 35 long-term haemodialysis patients and 36 uraemic patients undergoing their first dialysis session. Predialytic cell-associated IL-1 concentrations in freshly isolated monocytes were significantly increased both in long-term haemodialysis and first-dialysis uraemic patients compared to normal individuals. In both groups in comparison to normal individuals, although intracellular TNF alpha could not be detected in freshly isolated monocytes, both extracellular IL-1 and TNF alpha concentrations were greatly increased after 20 h of in vitro culture of monocytes in the absence of exogenous stimulation and in serum-free conditions. However, long-term haemodialysis patients showed higher values of secreted IL-1 than not-yet dialysed uraemic patients. During a single dialysis session a significant increase in both cell-associated and secreted IL-1 but not TNF alpha was observed in long-term haemodialysis patients. In contrast, no change in the concentration of either cytokine could be detected at the end of the first dialysis session in uraemic patients. Our findings strongly suggest that factors related to uraemia could be a sufficient signal to initiate intracellular IL-1 protein synthesis and TNF alpha release by monocytes, but that greater IL-1 release could be stimulated during the periodic haemodialysis procedure.     

Endothelin in chronic renal failure.

The aims of the present study were to determine plasma endothelin (ET) in chronically uraemic patients, the renal clearance of endogenous ET in normal dog and man, and the effect of acute volaemic expansion on ET. The mean plasma ET concentration in haemodialysis patients was 57.5 +/- 5 pg/ml before haemodialysis and remained unchanged at 52.5 +/- 5 pg/ml after haemodialysis. They were thus significantly elevated both before and after haemodialysis (P less than 0.01) compared with plasma ET in normal subjects of 20.8 +/- 0.8 pg/ml. There was no evidence of ET clearance across the cuprophane membrane of the dialyser. Resting plasma ET values in the 15 non-dialysed uraemic patients ranged between 20 and 52.5 pg/ml (mean 38.2 +/- 2.3 pg/ml), significantly greater than those observed in controls (P less than 0.01). In CAPD patients, plasma ET was also significantly (P less than 0.01), elevated (63 +/- 10 pg/ml) when compared to controls, and similar to those observed in patients before haemodialysis. In dogs, mean ET did not diminish between the aorta and the renal vein (28.1 +/- 1 versus 28.4 +/- 2 pg/ml). In man mean ET did not significantly decline between the renal artery and the renal vein (17 +/- 3 to 13 +/- 0.8 pg/ml). In the seven healthy subjects who received 2000 ml of isotonic saline intravenously ET remained unchanged (24 +/- 2; 23 +/- 1 and 23 +/- 2 pg/ml before and 1 and 2 h after starting hydration respectively). We have thus shown that plasma ET is elevated in patients with chronic renal failure especially those on dialysis and CAPD.(ABSTRACT TRUNCATED AT 250 WORDS)     

不同剂量胰升血糖素样肽-1对大鼠肝切除术后糖代谢的影响

目的:探讨不同剂量胰升血糖素样肽-1（GLP-1）对大鼠肝切除手术后早期糖代谢紊乱的影响。方法:方法通过大鼠肝切除术观察手术后1 d葡萄糖耐量的改变与GLP-1，胰岛素(I)和胰升血糖素(G)的关系，以及静脉输注不同剂量GLP-1的影响。结果:大鼠肝切除术后第1天静脉葡萄糖耐量实验的峰值血糖及30 min血糖均明显高于正常对照组（ 均P<0.01），且曲线下面积（AUC 0-30）也明显高于正常对照组(P<0.01)；GLP-1低剂量组术后1 d峰值血糖与肝切除手术组间的差异无显著性（P>0.05）；GLP-1高剂量组术后1 d峰值血糖明显低于肝切除手术组和GLP-1低剂量组(P<0.05和P< 0.01)， 30 min血糖明显低于肝切除手术组(P<0.01), AUC 0-30明显低于肝切除手术组和GLP-1低剂量组(均为P<0.01)。肝切除手术组术后1 d胰岛素明显下降，胰升血糖素明显升高（P<0.05），致I/G值下降。GLP-1低剂量组术后1 d胰岛素明显低于高剂量组（P<0.05），胰升血糖素则明显升高（P<0.05），致I/G值明显低于高剂量组（P<0.01）。结论:大鼠肝切除术后早期，GLP-1的促进胰岛素分泌和抑制胰升血糖素释放的作用减弱，增加剂量后仍可增强其效应，进一步改善机体对葡萄糖的利用。     

Atrial natriuretic peptide and parathyroid hormone (1-84) in relation to noradrenaline induced changes in blood pressure in uraemic and healthy subjects.

In order to evaluate the hormonal regulation of blood pressure (BP) in uraemia 12 patients on chronic maintenance dialysis and 14 healthy controls were studied. BP and plasma concentrations of atrial natriuretic peptide (ANP), cyclic 3',5'-guanosine monophosphate (cGMP), and intact parathyroid hormone (PTH(1-84)) were determined before, during, and after a 60 min noradrenaline infusion 0.1 micrograms kg-1 body wt. min-1. Mean BP increased to the same extent in the uraemic patients (median 15 mmHg, range 6-25 mmHg) as in the controls (12 mmHg, 5-25 mmHg). ANP increased during noradrenaline infusion both in patients (7.2 to 8.3 pmol/l, medians, p < 0.01) and in controls (4.4 to 6.0 pmol/l, p < 0.01), and so did cGMP (patients: 31.6 to 35.9 nmol/l, p < 0.05; controls: 6.6 to 8.7 nmol/l, p < 0.01). PTH(1-84) was higher in the uraemic patients than in the controls, but was unchanged during noradrenaline infusion in both groups. Correlation analyses gave no evidence of a direct relation between BP and ANP, but basal PTH(1-84) was negatively correlated to basal mean BP in the patients (rho = -0.615, p < 0.05), but not in the controls. In conclusion, noradrenaline induced similar elevations of BP in dialysis patients as in healthy controls despite elevated ANP and PTH(1-84) in the patients, and ANP release was stimulated in both groups. PTH(1-84) may participate in blood pressure regulation in uraemic patients.