Uraemic toxic retention solutes depress polymorphonuclear response to phagocytosis

Previous studies from our laboratory have demonstrated thatthe activity of the hexose mono-phosphate shunt (HMS) pathwayin phagocytosisrelated respiratory burst is disturbed in end-stagerenal disease. To determine whether uraemic solute retentionis responsible for this defect the HMS-path was evaluated bymeasurements of glucose-1-C¹⁴ utilization and determinationof ¹⁴CO₂ production in polymorphonuclear cells (PMNLs), suspendedin normal plasma or uraemic biological fluids. Normal PMNLs,while suspended in normal or uraemic plasma, were stimulatedwith either latex, zymosan or Staph. aureus; CO₂ generation(measured as DPM/10³ PMNL, normal versus uraemic plasma) wasdepressed in uraemic plasma in response to latex (from 43±5to 20±3), zymosan (from 72±8 to 47±4) (P<0.01),and Staph aureus (from 73±17 to 47±8 DPM/10³ PMNL)(P<0.05). The degree of inhibition was similar for each stimulus.To characterize the substances responsible for this defect wefractionated uraemic plasma ultrafiltrate by polarity-basedsemipreparative C₁₈ reversed phase HPLC and found a decreasedresponse to Staph. aureus in the presence of fraction 2 (from102±13 to 23±10 DPM/10³ PMNL, P<0.05), andin fractions 8 and 11 (lowest value in fraction 8, 54±14DPM/10³ PMNL, P<0.05 versus control). The pattern of HPLCelution on a gradient from 100% formiate (pH 4.0) to 100% methanolindicates that there are at least two chemically distinguishablegroups of compounds, one hydrophilic (in fraction 2), and onelipophilic (in fractions 8 and 11). We conclude that uraemicbiological fluids contain factors that inhibit HMS activityrelated to phagocytosis, and that at least two groups of componentswith different characteristics are involved.     

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.     

Inhibition by uraemic sera of CD4+ T-cell adhesion to extracellular matrix components

BACKGROUND.: T-cell-mediated immune responses are impaired in patients withchronic renal failure. The migration, proliferation, differentiation,biological functioning, and interaction with other T cells aremediated by cell surface adhesion proteins, which include integrins. METHODS.: To elucidate how uraemia can impair T-cell-mediated responsesin vivo, the effects of sera from uraemic patients on T-cellproliferation and adhesion to extracellular matrix (ECM) componentswere examined. RESULTS.: Preincubation of human CD4⁺ T cells with sera from undialysedand dialysed (haemodialysis or peritoneal dialysis) uraemicpatients inhibited the capacity of the cells to be stimulatedby phytohaemmagglutinin and by anti-CD3 monoclonal antibodyplus immobilized fibronectin (FN). Sera from uraemic and dialysedpatients, but not from healthy individuals, inhibited significantly,and in a dose-dependent fashion, human CD4⁺ T cell adhesionto immobilized FN and laminin (LN). The degree of inhibitionof adhesion was similar whether the sera were continuously present,even during the adhesion assay, or removed by washing. The adhesioninhibiting capacity of the uraemic sera was not due to modificationof the expression of ß1 integrins on the surfacesof the T cells. CONCLUSIONS.: These results suggest that uraemia can impair the proliferativecapacity and adhesion of immune cells, and thus may affect normalimmune processes and contribute to the overall immune deficiencyobserved in patients with renal failure.     

Increased cytosolic free sodium in platelets from patients with early-stage chronic renal failure

Cytosolic free sodium concentration ([Na⁺]i) and sodium transportsystems were measured in intact platelets from 19 patients withearly-stage chronic renal failure and 33 healthy control subjectsusing the novel fluorescent dye sodium-binding-benzofuran-isophthalate.Resting [Na⁺]i was significantly greater in patients with chronicrenal failure compared to control subjects (40.8±3.1mmol/1versus 32.2±2.0 mmol/1, mean±SEM, P<0.05).After inhibition of Na-K-ATPase by 1 mmol/1 ouabain a highernet sodium influx was observed in platelets from patients withchronic renal failure compared to control subjects (49.8±8.7mmol/1 versus 28.5±5.2 mmol/1, P<0.05). The plateletNa-H exchanger was similar in the two groups. Cytosolic freecalcium concentration ([Ca²⁺]i) was measured using fura2 anddid not show significant differences between the two groups.To evaluate whether a circulating factor may be associated withelevated [Na⁺]i, a linked-enzyme Na-K-ATPase assay was included.Compared to control subjects plasma from patients with chronicrenal failure produced a significant inhibition of steady-stateNa-K-ATPase activity by 11.2±3.0% (P<0.01). It isconcluded that early-stage renal failure is associated withsignificant impairment of platelet sodium metabolism.     

Parathyroid hormone and platelet cytosolic calcium concentration in essential hypertension

To investigate the possible relationships between blood pressure,parathyroid hormone (PTH) and platelet cytosolic Ca²⁺ concentration([Ca²⁺]_i) in patients with essential hypertension, we studied17 patients with this disease aged 48±2 years and 17normotensive controls aged 44±3 years. Platelet [Ca²⁺]_iwas measured by spectrofluorimetry using the dye Fura-2 acetoxymethylester.Patients with essential hypertension displayed lower levelsof serum ionized Ca²⁺ (0.99±0.03 versus 1.1±0.01mmol/l, P<0.05) and higher serum intact PTH levels (37±3versus 26±2 pg/ml, P<0.01) than the normotensive controls.Although serum levels of intact PTH were significantly correlatedwith mean arterial pressure (MAP) in the combined group of subjects(r=0.42, P<0.05), there was no correlation when each groupwas considered separately. Resting platelet [Ca²⁺]_i was alsohigher in patients than in controls (57±3 versus 48±2nmol/l,P<0.005). When platelets were stimulated in vitro with thrombin,the increment in [ca²⁺]_i was also greater in patients than incontrols in the presence of extracellular Ca²⁺ (264±24versus 194±19 nmol/l, P<0.05) but not in its absence(123±12 versus 112±10 nmol/l). The thrombin-inducedincrement in [ca²⁺]_i was correlated with MAP in the hypertensivepatients (r=0.64, P<0.01) and in the combined group of subjects(r=0.42, P<0.05). There was no relationship between restingor thrombin-induced [Ca²⁺]_i and serum PTH in either group ofpatients or in the combined group of subjects. Furthermore,preincubation of platelets in vitro with PTH had no effect neitheron resting platelet [Ca²⁺]_i or on thrombin-induced incrementsin [ca²⁺]_i, both in the presence and in the absence of extracellularCa²⁺ in either group of subjects. Therefore, despite platelet[Ca²⁺]_i and serum PTH seem to be related to blood pressure,it appears that PTH does not participate directly in the elevatedplatelet [Ca²⁺]_i found in patients with essential hypertension.     

Bidirectional peritoneal transport of albumin in continuous ambulatory peritoneal dialysis

The present study was undertaken in order to assess bidirectionalperitoneal kinetics of albumin after simultaneous i.v. and i.p.injection of radioiodinated albumin tracers (¹²⁵I-RISA and ¹³¹I-RISA)in eight clinically stable uraemic patients undergoing continuousambulatory peritoneal dialysis (CAPD). The plasma volume, intravascularalbumin mass (IVM), and overall extravasation rate of albuminwere not significantly different from that found in healthycontrols. Albumin flux from the plasma into the peritoneal cavitywas 3.71 ± 0.82 (SD) µmol/h, which was only 3%of the overall extravasation rate (137 ± 52 µmol/h).Albumin flux from the peritoneal cavity into the plasma wassubstantially lower (0.22 ± 0.07 µmol/h, P<0.01).The net peritoneal accumulation of the albumin from plasma over4 h was 14 ± 3.2 µmol, which was significantlylower than the intraperitoneal albumin mass at the end of thedialysis (54 ± 19 µmol, P<0.01). This indicatesthat only about 25% of the albumin loss during CAPD occurs directlyfrom the plasma. The initial osmotic net filtration was 508± 302 ml. The volume flow equivalent to the albumin fluxwas 6.3 ± 1.5ml/h into the peritoneal cavity and 7.8± 1.9ml/h back into the plasma. Although minor, as comparedto the osmotic net filtration (508 ml), the albumin flux equivalentvolume (31.2 ml) exceeded the steady state filtration (25.2ml) significantly (P<0.01) during the 4 h investigation. In conclusion, albumin flux into the peritoneal cavity is smallcompared to the overall extravasation rate, but our resultssuggest that CAPD loss of albumin predominantly occurs fromthe subperitoneal interstitial space and only to a minor degreedirectly from the plasma. Albumin flux equivalent volume flowis relatively small and most probably represents peritoneallymph drainage.     

Comparison of succinylcholine with two doses of rocuronium using a new method of monitoring neuromuscular block at the laryngeal muscles by surface laryngeal electromyography

We compared the onset of neuromuscular block with succinylcholine(1 mg kg^–1) and two doses of rocuronium (0.6 and0.9 mg kg^–1) at the adductor pollicis muscle usingelectromyography (EMG) and acceleromyography (AMG), and at theadductor laryngeal muscles with a new electromyographic methodusing a disposable surface electrode attached to the cuff ofa tracheal tube. At the larynx, the mean (±SD) time to90% block and the onset time of succinylcholine (38±15and 47±19 s, respectively) were significantly shorter(P<0.01) than for rocuronium 0.6 mg kg^–1 (92±42and 106±38 s) and rocuronium 0.9 mg kg^–1 (52±31and 64±30 s). We found that, with comparable degreesof neuromuscular block, the onset time of succinylcholine atthe adductor pollicis was significantly shorter (P<0.01)than for rocuronium 0.6 mg kg^–1 and 0.9 mg kg^–1(EMG, 80±39 vs 145±48 s and 99±31 s; AMG,90±39 vs 124±53 s and 106±38 s). Clinicalduration at the adductor pollicis (AMG) was significantly longer(P<0.01) for both rocuronium groups than for succinylcholine(T₄:T₁=0.7, 54±18 and 77±21 vs 8±6 min).The surface laryngeal electrode proved non-invasive, easy touse and reliable in measuring onset of the neuromuscular blockat the larynx. Br J Anaesth 2000; 85: 251–5 ^* Corresponding author: Postfach 1367, D-66363 St Ingbert, Germany     

Compliance and effects of nutritional treatment on progression and metabolic disorders of chronic renal failure

Low-protein, low-phosphorus diets (LPD) are prescribed to patientswith chronic renal failure (CRF) to slow down the rate of progressionof CRF and to control uraemic symptoms. A satisfactory adherenceof patients to the prescribed diet is needed to meet these twogoals. We studied the compliance of CRF patients to a LPD providingdaily (per kg body weight) 0.3 g protein, 3–5 mg phosphorus,35 kcal, and supplemented with essential amino-acids and ketoanalogues.Forty CRF patients were studied for 23.3±10.8 months(range 12–45). Compliance to LPD was evaluated by dietaryinquiry and protein intake estimated from urinary urea excretion.According to compliance to LPD, patients were retrospectivelyassigned to the compliant (n=27) or the non-compliant (n=13)group. GFR measured by the urinary clearance of [⁵¹Cr]-EDTAwas identical in the two groups at the start of the study: compliantpatients 15.7±5.3 ml/mn, non-compliant patients 15.4±5.9ml/mn. The decrease of GFR was – 0.08±0.22 ml/minper month in compliant patients versus –0.31±0.37ml/min per month in non-compliant patients (P<0.02). Theseresults were not demonstrated if the progression of CRF wasassessed by the linear regressions over time of creatinine clearanceor the reciprocal of creatinine. Serum bicarbonate, serum phosphorusand PTH levels were corrected by LPD in compliant patients (P<0.005 for all parameters) but not in non-compliant patients.These results suggest that evaluation of compliance is necessaryto assess the response of CRF patients to LPD, whether the aimis to slow the progression of CRF or to control its metabolicconsequences. A beneficial effect of compliance to LPD was demonstratedupon these two goals.     

PULMONARY MECHANICS DURING GENERAL ANAESTHESIA: The influence of mechanical irritation on the airway

The changes in pulmonary resistance (R_L) and compliance (C_L),following airway irritation and surgical stimulation, were investigatedin 19 anaesthetized, paralysed patients. Thirteen were normal,while six had objective evidence of chronic obstructive pulmonarydisease (COPD). Broncho—carinal irritation with a suctioncatheter produced a 27% increase in R_L (0.58±0.32 kPalitre^–1 s to 0.74±0.40, P < 0.01) and a 10%decrease in C_L (0.87±0.19 litre kPa^–1 to 0.81±0.22,P < 0.01). These changes were associated with a significantincrease in systolic arterial pressure and heart rate duringclinical stages of anaesthesia (end-tidal enflurane, 1.3±0.4%,Pa_CO2 5.20±0.53 kPa). These changes did not correlatewith depth of anaesthesia, but all returned to the pre-irritationvalue within 5 min. There was no difference in subjects considerednormal and those with COPD. Surgical stimulation did not producesignificant changes in pulmonary mechanics; however, repeatedbroncho—carinal irritation during surgery was associatedwith a transient increase in R_L (P < 0.01). ^*Present address: Department of Anesthesiology, Sapporo MedicalCollege and Hospital, Sapporo, Japan.     

Modulation of platelet cytosolic calcium during erythropoietin therapy in uraemia

Erythropoietin therapy for uraemic anaemia is associated witha high rate of hypertensive and thrombotic complications. Themechanism is unknown, but a change in cellular calcium controlmay be relevant to changes in blood pressure and thrombosis. Platelets were utilized as a model of vascular smooth musclecells. The effects of erythropoietin therapy on platelet cellularcalcium, assessed by fura-2, were meas ured in 25 patients receivingrenal replacement therapy during a 6-month treatment period. Three patients failed to reach a target haemoglobin and wereexcluded from the analysis. Blood pressure increased in 11 ofthe remaining 22 subjects, eight requiring an increase in antihypertensivemedication. There were no differences in cellular calcium controlbetween the group in whom blood pressure rose and patients withstable blood pressure. Overall there was a fall of 24% in restingcytosolic calcium (baseline 69.2 ± 5.1 to 52.5 ±3.0 nmol/1, P<0.05) after 3 months of erythropoietin therapy.There was no change in the thrombin-stimulated peak responsein the presence of extracellular calcium during therapy, althoughthrombin-stimulated intracellular release also fell at 3 months(baseline 769±61 versus 3 months 559±49nmol/l,P<0.01 This study suggests that intracellular free calcium controlwithin platelets improves in response to erythropoietin therapy.However these changes appear not to be related to the developmentof hypertension.     

The calcitonin-calcium relation curve and calcitonin secretory parameters in renal patients with variable degrees of renal function

Increased calcitonin (CT) levels have been reported in chronicrenal failure, even before the uraemic phase and in the absenceof hypercalcaemia. Furthermore, a sigmoidal CT-calcium relationshipwas recently observed in rats and haemodialysed patients. We carried out the present investigation in order to assess:(a) whether the sigmoidal CT-calcium relationship is also evidentin renal patients with a variable degree of renal failure andin normal subjects; (b) whether the four secretory parametersalready described for the PTH-calcium relation curve might bedescribed for CT too; (c) whether any change in some, if any,of these secretory parameters could be found at a variable degreeof renal insufficiency. We studied 33 renal patients (RP), with a variable degree ofrenal failure (creatinine clearance ranging from 16 to 164ml/min),and 10 normal subjects (C). All RP and C were submitted to abasal evaluation including the assessment of (1) basal concentrationsof 1,25(OH)₂ vitamin D, 25(OH) vitamin D, mono-meric CT, intactPTH; (2) GFR by Cr⁵¹EDTA clearance. On the 2 subsequent days,a hypocalcaemic test (Na₂-EDTA about 37 mg/kg of body-weight/2h) and a hypercalcaemic test (Ca gluconate giving 8 mg/kg body-weight/2h of Ca element) were carried out for the assessment of bothCT and PTH secretory parameters. According to GFR values, theRP were divided into three groups: group RP1 (GFR > 70 ml/minper 1.73 m²; n = 10), group RP2 (GFR between 30 and 70 ml/minper 1.73 m²; n=15), group RP3 (GFR < 30 ml/min per 1.73 m²;n = 8). In most, but not all, RP and C a sigmoidal CT-calcium relationshipwas evident, opposite in direction to the PTH-calcium relationcurve. In these RP and C the four secretory parameters, characteristicfor the PTH-calcium secretion curve, were calculated for CTtoo. When pooled RP and C were considered, both minimal (9.0± 6.4 pg/ml) and maximal CT levels (71.8 ± 56.2pg/ml) significantly differed from basal levels (24.3±18 pg/ml; P<0.001). The CT set point (CT SP) and sensitivity(CT SENS) values were significantly higher and lower than thecorresponding PTH secretory parameters (CT SP 1.39 ±0.08 mmol/1, PTH SP 1.23 ± 0.05 mmol/1,P<0.001) (CTSENS 243 ± 67%/mmol, PTH SENS 598 ± 329%, P<0.001).However, the CT SP values were strictly correlated with PTHSP values (r = 0.78, P<0.001). When CT secretory parameterswere considered separately in the RP groups, increased levelsof basal (36.1±28.6pg/ml), minimal (17.9±10.4),and maximal (139.9 ± 39.7) CT levels were found in theRP3 group, when compared with both the other RP groups and C.No significant difference was found as regards the CT SP andCT SENS values between RP and CT. These results suggest that (1) CT secretion is homeo-staticallycontrolled by calcium changes in the same range of the PTH-calciumsystem; (2) a sigmoidal CT-calcium relationship is demonstrablein most (but not all) RP and C; in these subjects it is possibleto calculate the CT secretory parameters as for PTH; (3) theincrease in CT levels in the course of chronic renal failureis quite similar to the already known increase of PTH, and ischaracterized by the increase of basal, minimal and maximalCT values, suggesting that an increased secretion of CT by thethyroid C-cells (rather than CT retention due to a decreasein renal function), is responsible for these findings.     

Time course of inulin and creatinine clearance in the interval between two haemodialysis treatments

BACKGROUND: Urinary volume of haemodialysis patients with residual renalfunction increases during the interdialytic interval. The contributionof GFR to this change in water and solute excretion has notbeen quantified in detail. The creatinine clearance (Cl^c) asa determinant of the GFR may overestimate GFR caused by thetubular secretion of creatinine. Cimetidine has been used toinhibit the secretion of creatinine in non-dialysed patients.No data are available on its usefulness in haemodialysis patients. METHODS: Two identical interdialytic intervals (DI) of 3 days (DI-1,DI-2) were investigated in 11 patients. The interval betweenDI-1 and DI-2 was 1 week. During DI-2 cimetidine 800 mg dailywas administered. Each DI was divided in four urine-collectionperiods. RESULTS: The water and solute excretion in DI-1 and DI-2 were similar.Urinary production increased from 0.37 ±0.30 ml/min to0.66 ±0.33 ml/min (P<0.05), inulin clearance (C1¹)increased from 1.8±1.1 ml/min to 2.7 ± 1.2 ml/min(P<0.05), fractional sodium excretion from 9.0 ± 5.7%to 14.5 ± 9.0% (P<0.05). In contrast to Cl_i;; theCl_c showed no increase during the interdialytic interval bothin DI-1 and DI-2. The overestimation of GFR by creatinine (Cl_i– Clⁱ) decreased during DI-1 from 1.35 ±1.69 ml/minto 0.26 ± 0.60 (P<0.05) and during DI-2 from 1.01±1.33 ml/min to 0.10 ± 0.67 (P<0.01). The ratioCl^c/Clⁱ decreased during DI-1 from 1.78 ± 0.53 to 1.09± 0.19 (P< 0.01) and during DI-2 from 2.02 ±1.13to 1.05 ± 0.30 (P<0.01). All parameters were not differentbetween the comparable days of DI-1 and DI-2. CONCLUSION: We conclude that the urinary volume in the interdialytic intervalis directly related to changes in GFR. During the interdialyticinterval GFR increased and tubular secretion of creatinine decreased.The administration of cimetidine did not improve the accuracyof Cl_c as a measurement of GFR in end-stage renal failure.     

Adequacy of dialysis and nutritional status in CAPD

Urea kinetic modelling (UKM) was used to assess adequacy ofdialysis in 50 CAPD patients. Nutritional status was assessedfrom the measurement of visceral protein status (total protein,albumin, transferrin, immunoglobulins, complement), somaticprotein status (anthropometry), and dietary intake (1 week weigheddietary inventory and normalized protein catabolic rate (NPCR)from UKM). Morbidity was assessed from the peritonitis and admissionhistory. Mean Kt/V (corrected to x3 weekly dialysis) was 0.66 ±0.02. Dietary protein intake estimated from the NPCR (1.08±0.03g kg^–1 day^–1) correlated well (r=0.72, P<0.001)with that estimated from the dietary inventory (1.10±0.04g kg^–1 day^–1). There was a strong correlation betweenKt/V and NPCR corrected for actual weight (r=0.65, P<0.001),but when NPCR was corrected for IBW this correlation was weaker(r=0.35, P<0.05). Patients were divided by Kt/V into twogroups (>0.65, n=22 and <0.65, n=28). There were no significantdifferences in the indices of visceral protein status betweenthe two groups. Weight, height, BMI, fat free mass and arm musclearea were significantly greater in the group Kt/V<0.65. Residualrenal function (creatinine clearance) was higher in the groupKt/V>0.65 (3.8±0.7 versus 1.9±0.5 1/24 h, P<0.05)and plasma creatinine less (913±51 versus 1265±51µmol/l, P<0.001). Hb, potassium, bicarbonate, phosphate,alkaline phosphatase, PTH, and blood pressure were not different.Neither was there any difference between the two groups in anyof the indices of morbidity.     

Renal effects of maintenance low-dose cyclosporin A treatment in psoriasis

The renal effects of low-dose cyclosporin A (CsA) treatmentin severe psoriasis was investigated in 10 patients treatedwith a mean CsA dose of 3.23 (range 1.94–4.10) mg/kg/dayfor 12 months. The psoriasis area and severity index was reducedby 63–76%. Ambulatory GFR (iothalamate-¹²⁵I) ERPF (hippuran-¹³¹),RVR and MAP were examined at 3-months intervals. A control renalbiopsy was performed shortly before treatment start and a secondbiopsy was taken after 12 months of therapy. GFR was slightlybut significantly reduced after 6 and 9 months; after 12 monthsthe decrease was not significant (121.0±7.6 versus 115.2±7.8ml/min/l.73M P>0.10). After 12 months serum creatinine increasedfrom 82±4 to 94±7 µmol/litre (P<0.05while an insignificant increase of ERPF was seen and FF decreasedfrom 0.29±0.01 to 0.26±0.01 (P<0.05). MAP remainedunchanged. GFR and serum creatinine correlated significantlywithin each 3-month interval. A slight de novo interstitialfibrosis was seen in the second biopsy in 4 of 10 patients receivinga mean CsA dose of 3.2–4.1 mg/kg/day. In three of thesepatients a concomitant rise in serum creatinine was seen. In conclusion, low-dose CsA was associated with reversible fallin GFR and potentially progressive structural changes not alwaysaccompanied by corresponding functional alterations. One shouldconsider reducing the daily dose of CsA to 3.0 mg/kg body- weightor less in CsA therapy up to 1 year.     

PHARMACOKINETICS OF ALFENTANIL IN CHILDREN UNDERGOING SURGERY

Alfentanil pharmacokinetics and protein binding were deteminedin 20 children aged 10 months 6.5 yr. The data were comparedwith those from 10 adult patients. Eighteen children receiveda single i.v. dose of alfentanil 20 µg kg^–1 Theapparent volume of distribution (V^ß) did not differbetween the two groups. The degree of plasma protein bindingwas also similar in children and adults with mean free fractionsof 11.5±0.9% (±SD) and 11.8±3.9%, respectively.There were marked differences in the elimination half-life ofalfentanil (63±24 min in children; 95±20 min inadults (P < 0.001)) and plasma clearance of alfentanil (11.1±3.9ml min^–1 kg^–1 in children and 5.9±1.6 mlmin^–1 kg^–1 in adults (P < 0.001)).     

VERAPAMIL AS A HYPOTENSIVE AGENT DURING NEUROLEPTANAE STHE S IA

The haemodynamic effects of verapaniil were investigated in11 patients anaesthetized with thiopentone, fentanyl and dehydrobenzperidol.Suxamethonjpm and pancuronium bromide were used for muscle relaxation.Verapamil 0.07 mg^–1 given as a single intravenous bolusdecreased mean arterial pressure from 108±18mm Hg to84±2OmmHg (P<0.001) and total peripheral resistanceby 29±10% from 1662±399dynes cm^–1 (P<0.001)while heart rate and mean pulmonary artery pressure showed onlyminor changes. The decrease in arterial presstir was causedby reduction in total peripheral resistance while cardiac outputwas increased.     

Interleukin-1{beta} induces the formation of nitric oxide in isolated juxtaglomerular cells: influence on renin secretion

Renin secretion may be modulated by nitric oxide (NO). We studiedwhether interleukin-lß (IL-1ß) induces endogenousNO synthesis in mouse juxtaglomerular cells (JGC) in primaryculture, and whether endogenous NO or NO applied exogenouslyvia sodium nitroprusside (SNP) influences renin secretion. JGCseeded on culture plates were stimulated by IL-1ßor by SNP. Cyclic guanosine 3', 5'-monophosphate (cGMP) in thecell supernatant was determined as indicator for NO effects.Stimulation of JGC with IL-1ß or SNP increased cGMPin the supernatant significantly. The NO synthase inhibitorsN^G-nitro-L-arginine or N^G-monomethyl-L-arginine, or the NO scavengeroxyhaemoglobin prevented the IL-1ß-induced increaseof cGMP. The biological activity of NO was shown in a bioassayby the vasodilatory effect of the effluent from an IL-1ß-stimulatedJGC column on a precontracted rat aortic ring and was preventedby oxyhaemoglobin and methylene blue. Renin activity of JGCwas detected in the culture supernatants and the cells. Spontaneousrenin secretion into the cell supernatant was 26±1%oftotal activity. Melittin or forskolin concentration dependentlyincreased renin secretion up to 90 ±2%. Incubation ofJGC with IL-1ß in the absence or presence of NO inhibitorsdid not alter spontaneous or stimulated renin secretion. SNP(30 µM) had a dual effect on renin secretion. After 1h of incubation, it inhibited basal renin secretion, whilstit had a stimulatory effect after 20 h of incubation. Melittin-or forskolin-stimulated renin secretion was not influenced bySNP. In summary, IL-1ß stimulates NO synthesis inJGC. Endogenous NO was without influence on renin secretion,whereas high concentrations of exogeneously applied NO had adual effect on renin secretion.     

PTH/PTHrP receptor mRNA is down-regulated in epiphyseal cartilage growth plate of uraemic rats

PTH/PTHrP receptor mRNA is down-regulated in epiphyseal cartilagegrowth plate of uraemic rats. Growth retardation, hypocalcaemia,hyperphosphataemia, and skeletal resistance to the action ofPTH are well known features of advanced chronic renal failure(CRF). It has been suggested that the downregulation of renaland skeletal PTH receptors (PTH/PTHrP-R) could play an importantrole in the occurrence of these abnormalities. In the presentstudy, four uraemic (4 weeks after 5/6 nephrectomy) and fourcontrol (sham-operated) rats were analysed for PTH/PTHrP-R mRNAexpression at the proximal femoral and tibial growth platesby in situ hybridization. Uraemic rats had plasma biochemicalabnormalities of advanced CRF including high creatinine, phosphate,and PTH, and low calcium and calcitriol levels. The femoraland tibial bones of uraemic animals were shorter in length thanthose of control rats, and had reduced width and cellularityof the epiphyseal cartilage growth plate. Mean (±SD)tibia growth plate width was 152±30 µm in uraemicrats, compared with 170±35 µm in control rats.The difference was mostly due to a marked reduction of the zoneexpressing PTH/PTHrP-R (mature chondrocytes) which was 30±5µm in tibias from uraemic versus 44±10 µmin tibias from control rats. The hybridization signals of PTH/PTHrP-Rper individual cell were quantified on dark field images usinga computer-assisted image analysis system. The number of grainsin PTH/PTHrP-R positive cells was also decreased in uraemicrats, 103±13 compared with 123±14 arbitrary units(dark pixel density)/cell in control rats (P 0.005). In conclusion,these data indicate that rats with severe CRF and secondaryhyperparathyroidism have reduced epiphyseal cartil age PTH/PTHrP-RmRNA expression. This alteration may be relevant in the pathogenesisof growth retardation in uraemia.     

PHARMACOKINETICS OF GLYCOPYRRONIUM IN URAEMIC PATIENTS

We studied the pharmacokinetics of glycopyrronium 11 uraemicpatients undergoing cadaveric renal transplantation and in sevenASA I control patients undergoing general surgery. Glycopyrronium4 µg kg^–1 was given i.v. before induction of anaesthesia.Blood and urine samples were collected for up to 24 h for measurementof glycopyrronium concentrations using a radioreceptor assay.Volume of distribution in the elimination phase (V^ß)was similar in both groups, the elimination half-life was longer (P <0.05), area underthe plasma concentration-time curve (AUC) larger (P <0.01)and plasma clearance (Cl) smaller (P < 0.01) in the uraemicpatients. In 3 h, mean 0.7 (range 0–3) % and 50 (21–82)% of glycopyrronium was excreted in the urine in the uraemicand healthy patients, respectively (P <0.001). The 24-h renalexcretion was 7 (0–25) % in uraernic and 65 (30–99)% in control patients (P <0.001). We conclude that the eliminationof glycopyrronium is severely impaired in uraemic patients.     

DIURETIC-INDUCED HYPOKALAEMIA, PANCURONIUM NEUROMUSCULAR BLOCKADE AND ITS ANTAGONISM BY NEOSTIGMINE

The effect of hypokalaemia on a neuromuscular blockade inducedby pancuronium and its antagonism by neostigmine was studiedin the cat anterior tibialis-peroneal nerve preparation usingthe constant infusion of pancuronium technique. Hypokalaemiawas induced by chronic administration of chlorothiazide. Theinfusion rate of pancuronium required to maintain a 90% depressionof twitch tension was reduced from 0.72 ±0.06 µgkg^–1 min^–1 in the cats with a normal serum concentrationof potassium (K⁺ = 4.4±0.2 mmol litre^–1; n = 7)to 0.41±0.07 µg kg^–1 min^–1 in the hypokalaemiccats (K⁺ = 2.3±0.1 mmol litre^–1; n = 8). The doseof neostigmine necessary for 50% antagonism of the pancuronium-induceddepression of twitch tension (ED₅₀) was 10.0 µg kg^–1in the cats with a normal potassium concentration and 18.5 µgkg^–1 in hypokalaemic cats. We conclude that hypokalaemiadecreases the dose of pancuronium required for neuromuscularblockade and increases the dose of neostigmine required forantagonism of the block.