[The concept of ultrapure solution online production]. / Il concetto di produzione online di liquido ultrapuro.

Online preparation of dialysis fluid, i.e., continuous mixing and immediate use, was introduced in 1964 and has contributed significantly to the expansion of dialysis therapy through simplified handling, improved microbiology, and enhanced efficiency. Online prepared replacement solution for hemofiltration was shown to be clinically safe as early as 1978, but the implementation was delayed for 20 years because of regulatory conservatism. Online preparation of sterile and pyrogen-free solutions for infusion is based on the use of water and concentrates that are mixed and distributed in a hygienically designed and maintained flow path. Ultrafilters with known retention capacity are placed in strategic positions to remove bacteria and endotoxins, which gives a sterility assurance level of at least six magnitudes, as required by the pharmacopoeia for sterile products. Microbiologic testing of the fluid should be applied when designing, validating, and troubleshooting online systems but not for routine quality control, because it only gives retrospective information. Quality assurance has to be built into a system and the way it is operated. The use of ultrapure dialysate must be considered as a suitable option for all hemodialysis modalities. To achieve this goal, one must keep in mind that ultrapure dialysate and infusate result from a complex chain of production where ultra-purity and/or sterility of the final solution relies on the weakest or worst component of the chain. Online fluid preparation, when properly performed, is safe, simple, and cost-effective and enhances the efficiency as well as the biocompatibility of dialysis therapy.

Tumor necrosis factor stimulates amino acid transport in plasma membrane vesicles from rat liver.

Severe infection is characterized by a translocation of amino acids from the periphery to the liver, an event that is mediated in part by cytokines such as tumor necrosis factor-alpha (TNF). We investigated the activities of Na(+)-dependent transport systems A, ASC, and N in hepatic plasma membrane vesicles (HPMVs) prepared from rats treated with TNF in vivo. TNF did not alter sodium uptake but resulted in time- and dose-dependent fivefold and 50% maximal increases in system A and system N activity, respectively, in HPMVs secondary to an increase in the transport Vmax. Maximal increases in transport were observed 4 h after exposure to TNF and had returned to basal levels within 24 h. Similarly, system ASC activity was stimulated 80% in HPMVs from rats treated with TNF. Incubation of HPMVs from normal rats in vitro with TNF did not alter transport activity. Pretreatment of animals with the glucocorticoid receptor antagonist RU 38486 attenuated the TNF-induced enhancement in transport activity by 50%. The marked increase in Na(+)-dependent amino acid transport activity by TNF is mediated in part by the glucocorticoid hormones and represents an important mechanism underlying the accelerated hepatic amino acid uptake that occurs during critical illness.

The catheter as Ariadne's thread to follow the path of Peritoneal Dialysis (PD) through the long-term experience of a Center.

In our institution, the first patient was treated by HD in 1955. In the middle of the '60s, the PD technique, revised by Maxwell (1), was implemented. The access to peritoneum was obtained by repeated puncturing of the abdomen, the catheter being removed after each session. In 1966, our first results on one year of PD were published (20 patients treated, 13 affected by ARF and 7 by CRF, for a total number of 150 sessions). Since 1967, the procedure of the repeated punturing was improved by the Seldinger technique. The efficiency of the PD intermittent treatment was increased with the "fast shift" schedule and PD automation was pursued with the project of a cycler (1968). The first CRF patients were treated by fast shift PD. In the late intermittent PD phase, the adoption of permanent catheters, destined to endure in our practice, the rigid and the soft indwelling for long-term treatments, allowed us to launch programs of home and nocturnal PD. With the incoming CAPD age, the greatest care was directed to the role of the catheter. The adoption of the surgical insertion by paramedian approach through rectus muscle, minimized, in our experience, the early complications. With the reduction of peritonitis rate, the later catheter complications increased in terms of patient discomfort, hospitalization and technique survival. On those grounds, in our institution a prospective trial on a ten year period was undertaken to compare, in terms of late complications rate, new versions of the classic Tenckhoff straight catheter (ST). The surgical insertion method was adopted for all the types, for a total of 196 catheters in 163 CRF patients. The tip displacement rate (12.2% with ST) decreased, albeit non significantly, with Swan Neck (7.9%), but was markedly and significantly reduced (1.0%) with the Self-Locating (SL) catheter experience. The surgical insertion of SL was comparable to that of ST. For those reasons, in recent years, in our institution the SL catheter became the first choice catheters for CRF patients.

High level expression and purification of the enzymatically active cytoplasmic region of human CD45 phosphatase from yeast.

The cytoplasmic region of human CD45 corresponding to residues 584-1281 was inserted downstream of the alcohol dehydrogenase promoter and transfected into a haploid strain of yeast. Expression of recombinant CD45 in yeast reached as high as 5% of the soluble protein. Following removal of cellular debris by centrifugation and an ammonium sulfate precipitation step, the enzyme was purified using phenyl-Sepharose chromatography, preparative gel filtration, Mono Q anion exchange chromatography and a final analytical gel filtration step. Enzymatically active material with a purity of > or = 98% was obtained with a yield approaching 50%. The final product gave a Km of 5.5 mM and a Vmax of 87.5 U/mg with p-nitrophenylphosphate and a Km and Vmax of 0.167 mM and 185 U/mg, respectively, with a phosphotyrosine peptide. The native enzyme purified from Jurkat cells showed comparable Kms with both substrates to the recombinant enzyme but displayed substantially lower Vmax values for both substrates.

Stimulation of hepatocyte System y(+)-mediated L-arginine transport by an inflammatory agent.

BACKGROUND: Arginine participates in several distinct metabolic pathways, including polyamine and nitric oxide biosynthesis. Normally, arginine is effectively sequestered from the hepatocyte intracellular space by the low basal activity of membrane transport system y+. This has implications for the subsequent metabolism of arginine and for hepatic arginine requirements during a septic insult. We investigated the influence of tumor necrosis factor (TNF) on the activity of System y(+)-mediated hepatocyte arginine transport employing hepatic plasma membrane vesicles (HPMVs). METHODS: Rats were treated with a single intraperitoneal injection of TNF (50 or 150 micrograms/kg body weight) for 2, 4, or 24 hours, and HPMVs were prepared by Percoll density gradient centrifugation. Vesicle purity was established by assay of enzyme markers. Vesicle arginine transport activity was evaluated by measurement of tritiated arginine uptake employing a rapid mixing-filtration technique. RESULTS: Arginine transport by HPMVs was entirely independent of sodium and consisted of saturable and nonsaturable components. Prior treatment with TNF resulted in a time- and dose-dependent stimulation of saturable transport within 2 hours and a return to basal levels after 24 hours. Nonsaturable uptake was unchanged. Inhibition analysis indicated that the TNF-induced increase in saturable arginine transport activity was mediated by an increase in System y+. Kinetic analysis revealed that accelerated transport was caused by a 78% increase in the maximal velocity of transport without alteration in transport affinity. CONCLUSIONS: In vivo treatment with TNF results in a rapid stimulation of saturable, System y(+)-mediated arginine transport in the liver. This TNF-induced stimulation of hepatic arginine transport may serve to increase the normally restricted availability of extrahepatic arginine to the hepatocyte intracellular space during a septic insult to support important arginine-dependent pathways in the liver.

Beta-2-microglobulin serum profiles in different settings of mass transport and fluid pyrogen content.

Different beta 2-microglobulin (beta 2m) serum profiles have been related to dialytic membranes, mass transport and/or patient immune stimulation. Eight patients were followed by cycles of four sessions: hemodialysis (HD), hemodiafiltration (HDF), acetate-free HDF (AFH), hemofiltration (HF) by filters on synthetic membranes (polysulphone = 4; methylmethacrylate = 4); pre- (A) and post- (B) measurements in the fourth session, and at the start of the next one (C), beta 2m lipopolysaccharide content of the fluids (LPS), and monocytes in vitro and spontaneous production of interleukins (IL); IL-1-IL-6 and tumor necrosis factor (TNF) were measured. In HD, beta 2m (mg/liter), corrected for ECV distribution, did not change (A = 36.5 +/- 10, B = 37 +/- 9, C = 36.4 +/- 9.7). In HDF, lower basal beta 2m (P < 0.001; A = 26.5 +/- 9) still decreased (B = 9.13 +/- 6.2), boosting subsequently to C = 21.6 +/- 14, as in AFH (A = 24.5 +/- 7, B = 11.2 +/- 2, C = 25.3 +/- 9) and in HF (A = 26.6 +/- 7; B = 8.5 +/- 4; C = 25.6 +/- 11). LPS (EU/ml) decreased (P < 0.001) from HD fluids (0.41 +/- 0.1) to HDF (0.28 +/- 0.1), AFH (0.15 +/- 0.1) and HF (0.04 +/- 0.05) but IL-1 and IL-6 were found in greater concentrations in HDF and AFH versus HD and HF, probably due to back-filtration. Beta 2m in different modes of dialytic treatments seem better correlated with the amount of convective transport rather than with the selected markers of immune stimulation.

Alpha 1-adrenergic receptors in the brain: characterization in astrocytic glial cultures and comparison with neuronal cultures.

Binding of [125I]HEAT to membranes prepared from primary cultures of astrocytic glial cells was time-dependent and 70-85% specific. Various adrenergic agonists and antagonists competed for [125I]HEAT binding according to the potencies of prazosin greater than, yohimbine greater than or equal to, clonidine, norepinephrine (NE), and propranolol. Scatchard analysis showed the Bmax of 209 fmol/mg protein and a Kd of 184 pM for [125I]HEAT binding by astrocytic glial membranes. Pretreatment of astrocytes with NE resulted in a dose-dependent downregulation of [125I]HEAT binding sites with a maximal response observed after 8 h at 100 microM NE. Removal of NE from cultures after pretreatment resulted in a time- and protein synthesis-dependent recovery of binding sites to control levels within 120 h. Incubation of astrocytic glial cultures with NE stimulated phosphoinositide (PI) hydrolysis in a time- and dose-dependent manner with a maximal stimulation of 2-fold observed in 60 min by 100 microM NE. Clonidine expressed differential effects on alpha 1-adrenergic receptors of the neuronal and astrocytic glial cultures. Pretreatment with 10 microM clonidine caused a 40% decrease in the Bmax of [125I]HEAT binding without influencing the Kd value in neuronal cultures. This downregulatory effect of clonidine was associated with a reduction in the ability of NE to stimulate PI hydrolysis in clonidine pretreated cells. In contrast to neuronal cultures, clonidine neither downregulated [125I]HEAT binding sites nor stimulated PI hydrolysis in glial cultures.

Mechanisms of accelerated hepatic glutamine efflux in the tumour-bearing rat.

The mechanisms potentially controlling the net release of glutamine by the liver that occurs in tumour-bearing rats were investigated. Studies were undertaken when the tumour comprised approximately 7% (15 +/- 2 g) of total body weight. Hepatic glutamine gradient ratios were calculated by dividing hepatic glutamine content by arterial blood glutamine concentration. Both sodium-dependent and sodium-independent hepatocyte carrier-mediated glutamine transport were evaluated employing hepatic plasma membrane vesicles (HPMVs). In TBR the hepatic glutamine gradient ratio doubled (P < 0.001) secondary to a 52% increase in hepatic content (P < 0.005) and a 16% decrease in circulating glutamine (P < 0.001). Sodium-dependent glutamine transport was increased in HPMVs from TBR secondary to a 24 +/- 4% increase in the maximal velocity of transport (Vmax; P < 0.01) without alteration in apparent transporter affinity (Km). Saturable sodium-independent carrier-mediated glutamine transport was increased in HPMVs from TBR over CONT to a much greater relative degree owing to a 2.7-fold increase in transport Vmax (P < 0.05) without a change in transport Km. The accelerated hepatic efflux of glutamine which characterizes malignant growth appears to be the result of both mass-action gradient phenomena and alterations at the level of hepatocyte membrane transport activity.

Atrial natriuretic factor and concomitant hormonal, hemodynamic and renal function changes after slow continuous ultrafiltration.

We treated a patient with refractory biventricular heart failure, dilutional hyponatremia and prerenal azotemia, by means of ultrafiltration. After ultrafiltration, gas exchange and cardiac output improved, with concomitant reduction of systemic and pulmonary vascular resistances. Despite a decrease of right atrial and wedge pressure, atrial natriuretic factor rose and plasma renin activity decreased.

Modelling the "ideal" self care--limited care dialysis center.

Limited care dialysis is an interesting option, which has gained attention in several settings because of the aging of the uremic cohort. The aim of this study was to assess its potential in the Piedmont region in northern Italy, evaluating patients' and care-givers' preferences and testing them in a mathematical model of organisation. The study was conducted in the satellite unit of a university hospital (200-210 dialysis patients), following 35 patients (15 at home, 20 in the center, 10 on daily dialysis). Opinions were collected with a questionnaire and features identified were empirically tested through a simulation model. Most patients (34/35) preferred a small unit, with a stable caring team. Further options were flexibility of dialysis schedule, multiple treatment options, integrated center/home care. These needs could be met by a flexible organization including conventional dialysis (3/week) and daily dialysis (6/week). We employed a simulation model (ARENA software) to calculate the nurses required for each shift and the opening hours and best schedule for the unit. Addition of daily dialysis (2-3 hours) to two conventional 4-5 hour sessions to increased the number of patients followed or "spared" beds, ensuring flexibility. According to patients' best choice (7 dialysis stations), and to the recorded calls, the needs are for two nurses per shift, two shifts per day and six nurses for up to 30 patients in limited care. In conclusion, small centers with flexible schedules can tailor dialysis to patients' needs. A managerial approach is valuable for testing cost/benefit ratios in specific contexts.

Limits of aortic stop flow infusion chemotherapy in the treatment of advanced cancer.

BACKGROUND: Advanced and relapsed tumors remain a challenging disease with a poor and dismal prognosis. Our choice for inoperable tumors consists in a percutaneous treatment strategy involving intra-arterial chemotherapy and hemofiltration, with previous blood stop-flow, which allows high doses of Cisplatin-cisplatinum, cis-diammine-dichloroplatinum (CDDP) and Mitomycin C (MMC) in the tumor-bearing area with minimal systemic toxicity. METHODS: We analyse the morbidity and mortality associated with stop-flow in 20 patients with unresectable and/or metastatic thoraco- abdominal tumors, non responders to prior systemic chemotherapy. RESULTS: In our experience, the rate of major side effects of the procedure was 31% with a mortality of 5%. The side effects were related to the radiological procedure and to the chemotherapic treatment. A 74-year-old patient died for acute kidney toxicity within 15 days after the procedure. The other transient toxicity symptoms recorded were: nausea, vomiting, increasing of creatinine levels, diplopia and appearance of necrotic ulcer associated to chemotherapic drugs. Concerning the complications related to the radiological technique, the main problem was the rupture of the balloon stop-flow catheter in four patients. CONCLUSIONS: Stop-flow is a new procedure that could develop in the future, thanks to the possibility of obtaining a higher dose intensity of chemotherapic drugs in districts or organs affected by advanced tumors, with less systemic side effects. Unfortunately, the uncertain results in terms of increasing survival and the default of effective devices are to be resolved for a wider application of the procedure.

How amino acids get into cells: mechanisms, models, menus, and mediators.

The bloodstream provides a readily available pool of amino acids, which can be taken up by all cells of the body to support the myriad of biochemical reactions that are essential for life. The transport of amino acids into the cytoplasm occurs via functionally and biochemically distinct amino acid transport systems that have been defined on the basis of their amino acid selectivities and physico-chemical properties. Each system presumably relates to a discrete putative membrane-bound transporter protein that resides within the cell membrane and functions to translocate the amino acid from the extracellular environment into the cytoplasm. Many of these transporters require sodium for maximal activity. The sodium-dependent model presented is consistent with "preferred random" kinetics, with sodium binding preferentially before the amino acid. The transporter acts as an enzyme that catalyzes the movement of its bound amino acid (and sodium) into the cell. In this review, the authors provide a conceptual view of the mechanism of carrier-mediated amino acid transport as well as an overview of the various models that can be used in the laboratory to study this process. In addition, the known agencies that accomplish transport and their regulation by nutrition, hormones, and other mediators of critical illness are discussed.

Cyclo-oxygenase blockade abrogates the endotoxin-induced increase in Na(+)-dependent hepatic amino acid transport.

BACKGROUND: Endotoxemia is characterized by a marked increase in the uptake of amino acids by the liver, but the regulation of this response has not been fully elucidated. In the current study, we investigated the potential role of prostaglandins as mediators of this response. We examined the in vivo effects of the anti-inflammatory agent ketorolac, a cyclo-oxygenase inhibitor that blocks prostaglandin synthesis, on hepatic amino acid transport activity in endotoxin-treated rats. METHODS: We assayed the activities of the Na(+)-dependent transport systems A and N in hepatic plasma membrane vesicles prepared from endotoxemic rats that were pretreated with ketorolac or vehicle. Hepatic plasma membrane vesicles were prepared by differential centrifugation, and the transport of [3H]glutamine (system N) and [3H]2-methylamino-isobutyric acid (system A) was assayed. Hepatic plasma membrane vesicles were also prepared from normal rats that received prostaglandin E2, and glutamine and MeAIB transport were measured. RESULTS: Endotoxin treatment resulted in a twofold to threefold increase in Na(+)-dependent amino acid transport activity in hepatic plasma membrane vesicles secondary to an increase in the transport Vmax, which was consistent with the appearance of increased numbers of corresponding transporter proteins in the hepatocyte plasma membrane. Pretreatment with ketorolac almost completely abrogated the endotoxin-induced increase in hepatic amino acid transport. Administration of prostaglandin E2 to normal rats resulted in a statistically significant increase in glutamine and alanine transport by hepatic plasma membrane vesicles prepared from these animals. CONCLUSIONS: Prostaglandins play a key role in mediating the accelerated hepatic amino acid transport that occurs during endotoxemia.

Impaired fibrinolysis in uremia: partial and variable correction by four different dialysis regimes.

In addition to a hemorrhagic diathesis, uremia is accompanied by a clotting tendency, caused by a marked fall in fibrinolytic capacity. Measurement of lysis time of whole blood diluted with phosphate and acetate buffers and of euglobulin lysis times showed that accumulation of inhibitors is primarily responsible. These probably belong to the class of small molecules abnormally retained in uremia. Hemodialysis (HD) offers the best method of correction, mainly because of better elimination of these inhibitors. In contrast, hemofiltration (HF) and, particularly, intermittent peritoneal dialysis (IPD) are much less effective. In IPD, protein loss via the peritoneum is also responsible for a loss of fibrinolytic activators, so that fibrinolysis becomes even poorer, exposing the patient to an increased risk of vascular complications.

Prevention and treatment of aluminum overload in uremic patients: long-term results.

The authors evaluate the efficacy of a protocol of prevention and treatment of aluminum (Al) overload in RDT patients during a 7-year period (from 1981, 164 patients, to 1987, 161 patients). Al in dialysate solutions was always less than 25 micrograms/l. Baseline Al levels greater than 100 micrograms/l were found in 22% of patients in 1981 but in none in 1987, while the percentage of values less than 60 micrograms/l increased from 55 to 91%. DFO tests were positive in 54% and 7% of cases in 1981 and 1987, respectively. A clinical diagnosis of Al intoxication was performed in 6 patients in 1981, and no further cases were diagnosed later. DFO treatment (50 mg/kg once a week) was employed preventively in 31 patients owing to positive DFO-tests, and in the 6 Al-intoxicated patients therapeutically. In the former patients none developed clinical intoxication. In the latter group clinical improvement was only temporary in the three parathyroidectomized patients. Al hydroxide [Al(OH)3] as a phosphate binder was tapered off in 1981 and substituted by Al-free chelants. In 1987, 66% of patients were given CaCO3 or Mg (OH)2 alone or in association, while 34% still needed Al(OH)3, although at low dosages (less than 2 g/day). The conclusion is that such a protocol is able to prevent and to treat cases of Al intoxication, albeit only partially.

Heparin transfer across the rabbit peritoneal membrane.

Variable quantities of heparin have been proposed to avoid intraperitoneal clotting during peritoneal dialysis without the risk of systemic effects, because heparin is presumed to be incapable of passing through the peritoneal membrane. This study set out to verify this assumption by using labeled heparin in experimental dialysis in 7 New Zealand white rabbits. Heparin was labeled with 99mTc. Labeling quality, assessed by two chromatographic checks, showed less than 5% of free pertechnetate. Chromatographic determinations showed more than 95 and 80% of labeled heparin in inflow and outflow dialysates and in blood samples respectively. Following sodium thiopental anesthesia, animals underwent three protocols: a single 15 min cycle of time diffusion with heparin 500 U/l (A), 6 successive 15 min cycles with heparin 500 U/l (B), and a single 3 h cycle with heparin 2,500 U/l (C). Labeled heparin was found in blood organs and urine in variable percentages. The total amount of recovered radioactivity ranged from 1.5% (A) to 20% (C) of that introduced. It may be concluded that heparin passes through the peritoneum according to some law dependent on the amount used and the diffusion time.

Ultrafiltration in the treatment of refractory congestive heart failure.

Artificial subtraction of fluids and solutes was evaluated in the course of acute and chronic heart failure when it became refractory to standard intensive medical treatment. A group of 19 patients (mean age 57 years), 9 with ischemic, 2 amyloidotic, 4 valvular, and 4 idiopathic cardiomyopathy, were treated. In 17 patients extracorporeal ultrafiltration (UF) by means of a polysulfonate ultrafilter was adopted along 125 sessions (105 assisted by a roller pump and 20 as a slow continuous ultrafiltrate). In two patients continuous peritoneal dialysis was adopted. In every case UF was well tolerated. Ultrafiltrate volumes ranged from 1680 to 3500 ml for every session with corresponding Na losses ranging from 194 to 434 mEq/session. Improved clinical and functional status with reduction of edema was observed in 17 of 19 patients. In 12 patients UF could be discontinued due to restored response to diuretics; 5 of these patients could subsequently undergo heart surgery (1 transplant, 3 valve replacement, 1 coronary bypass). The remaining 7 patients survived on medical therapy alone for an average of 228 days. In 7 of 19 cases, UF could not be discontinued, and these patients died after an average of 23 days of treatment. In conclusion, UF proved to be effective in eliminating salt-fluid overload and restoring response to medical treatment. Patients who are potential surgical candidates seem to be the most suitable for UF.

Prescription and surveillance of the acetate-free biofiltration sessions: the bicarbonate cycle.

A computerized system, structured by 4 different models concerning urea depuration, and bicarbonate and sodium handling in acetate-free hemodiafiltration has been conceived for integrated use covering each step of the therapeutic cycle, from a) the prescription of the session to b) its delivery, up to c) the dose-response analysis: the system, now fully developed for the bicarbonate cycle, covers both working areas; the medical one, with a program implemented on a Personal Computer, called Skipper which deals with steps a) and c), and the nursing area, with a program built into the dialytic equipment software. The Skipper program supports the prescription step (a) testing the session schedule by bicarbonate, sodium and urea kinetics. The dialytic equipment, (step(b)) using a different program, on the basis of the scheduled parameters memorizes the end-session plasma bicarbonate level and reacts to any modifications of the parameters regarding blood flow and fluid reinfusion flow suggesting opposite changes in order to reach the scheduled results. Finally (step (c)), the Skipper system statistically evaluates the observed end session bicarbonate plasma level with an expected value with upper and lower confidence bounds obtained by a multiple regression analysis performed on a large population of patients.

The production of platelet-activating factor during hemodialysis.

Regenerated cellulosic membranes (CU) induced the aggregation of plasma-free human neutrophils when recirculated in a dynamic model of dialysis without the patient on the circuit. Neutrophil aggregation was linked to the production of PAF by these cells. In the absence of detectable PAF production, no neutrophil aggregation occurred, as observed during recirculation with polymethylmethacrylate (PMMA) membranes. With polycarbonate (PC), PAF production and aggregation of neutrophils were both almost half the values with CU. PAF production was studied in ten hemodialysis (HD) patients tested twice with CU and once with PC and PMMA membranes. PAF was extracted in the venous blood during filling of the dialyser for 9/20 of patients with CU (3.1 +/- 2.9 ng/ml, mean +/- 1 S.D.) a membrane that induced marked leukopenia (greater than 50% of basal values at 15 min), C3a des Arg generation (greater than 500% at 5 min), and plasma levels of the elastase-alpha 1-proteinase inhibitor complex (greater than 500% at the end of HD). Membranes such as PC and PMMA showing intermediate or low potential to induce leukopenia and C3a des Arg generation, respectively, did not trigger the production and release of PAF in detectable amounts at any interval. However, with PMMA, plasma neutrophil elastase was significantly higher than baseline at the end of dialysis. These levels were not significantly different (p less than 0.05) from those observed with CU and PC membranes.

In vitro complement-independent activation of human neutrophils by hemodialysis membranes: role of the net electric charge.

Polymethylmethacrylate (PMMA) membranes with different net electric charges and percentage water contents (anionic 71%, neutral 70%, cationic 75%) were evaluated for their ability to stimulate plasma-free human polymorphonuclear neutrophils (PMN), and compared for potency to cuprophan (Cu), already described as being a potent trigger of PMN. The release of lysozyme, beta-glucuronidase, lactic dehydrogenase (LDH), and the generation of a platelet aggregating activity were studied in the supernatants from plasma-free human PMN incubated with different membranes. The PMN intracellular content of neutrophil cationic proteins (NCP), elastase, and cathepsin G were also studied by immunofluorescence using specific antisera on smears of PMN before and after incubation with each membrane. Only cationic, but not anionic or neutral PMMA induced a marked release of lysozyme (range 20-25% of the sonicated control, assumed as 100%), and beta-glucuronidase (40-43%), and marked depletion of the intracellular content of NCP, elastase, and cathepsin G, suggesting a degranulation process. Platelet aggregating activity was generated and referred to the release of platelet activating factor (PAF) only in the supernatants from PMN incubated with cationic, but not with anionic, or neutral PMMA membranes. These results indicate that modification of the net electric charge can per se turn PMMA, commonly recognized as inert, into a material with marked PMN activating effects, comparable to those of Cu, a highly reactive polymer.