Cocaine use, hypertension, and end-stage renal disease

Cocaine use has been associated with both acute renal failure and hypertension (HTN), but only recently have data suggested it may lead to a chronic insidious form of renal failure. We designed a cross-sectional study to compare the association of cocaine use in hemodialysis patients with and without a diagnosis of HTN-related end-stage renal disease (HTN-ESRD). Two hundred one black patients from two outpatient hemodialysis units in an urban community were evaluated. There were 193 eligible patients, 106 men and 87 women, aged 49.28 +/- 14.4 years. A history of significant cocaine use before dialysis was reported by 55 of 193 subjects (28.5%). A diagnosis of HTN-ESRD was reported in 49 of 55 cocaine users (89.1%) compared with 64 of 138 nonusers (46.38%; odds ratio, 9.44; 95% confidence interval, 3.79 to 23.49; P < 0.0005). Of the 113 subjects with HTN-ESRD, 49 subjects (43.4%) had a history of cocaine abuse, either alone or in combination with other drugs. Subjects with HTN-ESRD with cocaine use were younger than those without cocaine use (40.7 +/- 9.0 versus 53.8 +/-15.3 years; P < 0.0005) and had a shorter reported duration of HTN (5.3 +/- 5.4 versus 12.7 +/- 9.8 years; P < 0.0005, adjusted for age and sex). In our urban dialysis population, a clinical diagnosis of HTN-ESRD was strongly associated with a history of cocaine use and earlier onset of ESRD. Cocaine should be considered as a cause of ESRD in patients without a clear cause of renal failure.

A clinic and community-based approach to hypertension control for an underserved minority population: design and methods

This paper describes the design and methodology of the Community Hypertension Intervention Project (CHIP). CHIP is investigating the environmental and psychosocial factors related to treatment adherence and examining the effects of combining usual hypertension care with the effects of three interventions designed to improve patient compliance with treatment for high blood pressure in a high-risk, underserved minority population. Thirteen hundred and sixty-seven inner-city hypertension patients (75% black and 25% Hispanic) have agreed to participate in the 4-year longitudinal study. These participants were randomized to usual care or one of three intervention groups: individualized counseling sessions; home visits/discussion groups; or computerized appointment-tracking system. Participants are representative of the surrounding, predominantly low-income minority community and are treated in a hospital-based clinic and in a private clinic in the community. About 65% have blood pressure levels considered to be out of control. It was concluded that structural changes at the clinic site, along with the targeted interventions, would improve patient satisfaction, increase treatment adherence, and improve blood pressure control.

Technology evaluation: gene therapy (FGF-5), Vical

Vical, in collaboration with Merck, is developing gene-based therapies, including its 'naked DNA', for the potential treatment of ischemic heart disease. Vical has obtained preclinical data in animal models showing that a gene for a potent growth factor, FGF-5, can be delivered and expressed in coronary arteries stimulating the formation of new blood vessels. This new blood vessel formation may provide supplemental blood flow and necessary cardiac tissue oxygenation in areas of the heart where atherosclerotic blockages are present. Vical anticipates that its FGF-5 gene-based product would be used in conjunction with balloon angioplasty to stimulate new blood vessel formation at the site of the blockage. A series of experiments have been conducted in rats, whereby genes encoding FGF-5 were injected directly into rat heart muscle. The DNA was absorbed and the FGF-5 protein was expressed by cardiac myocytes. Active FGF-5 was released into the extracellular spaces of the heart muscle cells and new blood vessels formed throughout the local area. Quantitative measurements of blood vessel formation indicated that capillary density increased significantly in the hearts of treated rats compared to untreated controls. Further studies are underway to evaluate the persistence of new blood vessels following FGF-5 gene injection, and measurements will be made to assess the extent of improved blood flow in the affected region [177118]. In December 1996, the US patent office issued patent number US-05580859, covering Vical's naked DNA technology [227199].

Erythropoietin upregulates angiotensin receptors in cultured rat vascular smooth muscle cells

OBJECTIVE

Plasma renin is not elevated in recombinant human erythropoietin (rhEPO)-induced hypertension but angiotensin converting enzyme inhibitors reduce blood pressure in both human and animal studies. Since rhEPO elevates renin and angiotensinogen messenger RNAs in angiotensin II target tissues such as the aorta, we explored the actions of rhEPO on renin-angiotensin system-related gene transcription of cultured rat vascular smooth muscle cells.

DESIGN AND METHODS

To separate direct actions of rhEPO from those mediated secondarily by potential activation of the renin-angiotensin system, vascular smooth muscle cells were cultured with rhEPO and enalapril to inhibit the angiotensin converting enzyme and losartan to inhibit angiotensin II type 1 receptors.

RESULTS

Vascular smooth muscle cells cultured with rhEPO (6-8 units/ml) demonstrated elevations (40-120%) in messenger RNAs of the renin-angiotensin system (renin, angiotensinogen, angiotensin receptor types 1 and 2) and increased levels of several messenger RNAs known to respond to angiotensin II (transforming growth factor-beta, insulin-like growth factor-II, epidermal growth factor, c-fos and platelet-derived growth factor). In contrast, cells cultured in the presence of rhEPO and enalapril or losartan showed elevations of messenger RNA for only the two types of angiotensin II receptor. This increase was higher than that obtained when cells were cultured with rhEPO or either antagonist alone. The increase in specific binding of angiotensin II to cells cultured in the presence of rhEPO and enalapril or rhEPO and losartan paralleled the changes in receptor messenger RNA.

CONCLUSIONS

rhEPO exerts its primary action on vascular smooth muscle cells via an increase in angiotensin receptor messenger RNA, resulting in a parallel increase in angiotensin II receptor expression. We suggest that increased receptor expression secondarily mediates the expression of other renin-angiotensin system messenger RNAs, which leads to angiotensin II-responsive gene transcription. The elevation in angiotensin II receptors, as observed in response to rhEPO, may provide a mechanism by which other forms of renin-dependent hypertension are initiated.

Low density lipoprotein receptors mediate intracellular calcium signals in microalbuminuric hypertensives

Hyperlipidemia is an established risk factor for progressive renal damage and proteinuria. Platelets and vascular smooth muscle cells (VSMC) are known to possess low density lipoprotein (LDL) cholesterol receptors. We used platelet LDL receptors to investigate the hypothesis that elevated lipids could activate intracellular calcium [Ca2+]i signals, leading to altered vascular tone and permeability. We divided essential hypertensives into microalbuminuric positive (MA+) and negative (MA-) groups and measured baseline and LDL stimulated levels of [Ca2+]i. The MA+ group demonstrated a significantly higher mean baseline [Ca2+]i level (119.0 +/-24.5 v 86.2 +/- 25.4 micromol/mL, P = .001). The MA+ group also displayed greater elevations in [Ca2+]i levels after stimulation with LDL in concentrations of 10 and 25 microg/mL (100.9 +/- 54.8 v 40.9 +/- 20.2, P = .04 and 111.6 +/- 51.0 v 52.9 +/- 39.9 micromol/mL, P = .03, respectively). Our data indicate that hypertensive patients with early glomerular capillary injury display exaggerated influx of [Ca2+]i after LDL receptor stimulation. Heightened LDL receptor sensitivity may facilitate LDL mediated [Ca2+]i signals, leading to increased VSMC tone and proliferation and progressive renal disease.

The efficacy of lovastatin in lowering cholesterol in African Americans with primary hypercholesterolemia

PURPOSE

To evaluate the efficacy of lovastatin in African Americans (AA) diagnosed with primary hypercholesterolemia.

PATIENTS AND METHODS

Forty-seven AA patients from the King/Drew Medical Center in Los Angeles were recruited from the Hypertension, Family Practice, and General Medicine Clinics for a double-blinded, placebo-controlled trial. Forty-one patients completed the 10 week study. Eligibility for entrance into the study was determined by patient lipid profiles meeting the criteria for pharmacological intervention outlined by the National Cholesterol Education Program II guidelines. Patients were randomized into 2 groups: lovastatin 20 mg per day, or placebo. A registered dietitian counseled both groups on two visits during the study to ensure compliance with a low fat, low cholesterol diet. Lipid levels were compared at the first and last visit of the study.

RESULTS

The lovastatin-treated group demonstrated significant reductions in mean total cholesterol (TC) (14.7%, 95% confidence interval [CI]-6.6 to -22.8, P < 0.01) and low-density lipoprotein (LDL) cholesterol (20.0%, 95% CI-7.9 to -32.1, P < 0.01) from baseline. Plasma triglyceride (TG) levels decreased by 10.5% (95% CI-2.4 to -18.6) and total cholesterol/high density lipoprotein (HDL) ratio fell below five in the lovastatin group, but neither reduction reached statistical significance. Placebo administration was not associated with any significant changes in TC, LDL, or TG. There were no significant differences between baseline and post-treatment hepatic transaminase levels in either group.

CONCLUSIONS

The HMG-CoA (3-hydroxyl-3 methylglutary coenzyme A) reductase inhibitor lovastatin in a dose of 20 mg per day was effective in decreasing TC, LDL, and TG levels in an AA population. Considering that the AA population is at substantially increased risk for hypertension and cardiovascular morbidity, more aggressive and wider use of HMG-CoA reductase inhibitors should be employed in reducing elevated plasma cholesterol levels.

Paracellular phosphate absorption in rat colon: a mechanism for enema-induced hyperphosphatemia

The mechanism of colonic phosphate absorption is not well defined. We measured unidirectional phosphate fluxes across rat distal colon epithelium in the absence of transepithelial electrochemical gradients. Steady-state mucosal-to-serosal flux (Jms) was not different from the serosal-to-mucosal flux (Jsm), generating no net flux (Jnet = Jms - Jsm, was not different from "0'). Simultaneous fluxes of mannitol, a paracellular probe, exhibited an identical flux pattern, suggesting that phosphate flux across the colonic epithelium may be mediated through the paracellular pathway. Tight junction permeability was increased with mucosal addition of taurodeoxycholate (TDC, 2 mM) which caused a prompt increase in transepithelial conductance from 7.03 +/- 0.35 to 13.88 +/- 0.35 mS/cm2 (p < 0.001). This was associated with an increase in Jsm, but no change in Jms, for mannitol, resulting in a net flux in the secretary direction. Identical TDC-induced changes were observed in phosphate fluxes, again suggesting phosphate permeation through the intercellular, mannitol pathway. A significant correlation was observed between the permeability of phosphate and the permeability of mannitol, measured both in the mucosal-to-serosal and the serosal-to-mucosal directions and under both control and experimental (mucosal TDC) conditions. Thus, colonic phosphate transport is mediated through the paracellular pathway and enema with high phosphate concentrations (1,760 times blood concentration), can trigger rapid and massive phosphate absorption through this diffusive pathway.

Acquired cystic disease in chronically rejected renal transplants

Acquired cystic disease has been documented to complicate most forms of chronic renal damage; it has only infrequently been described in transplanted kidneys. Five patients with noncystic ESRD and chronically rejected transplants in which acquired cystic disease arose are reported. The diagnosis of acquired cystic disease was established in examination of transplant nephrectomies from four patients and a core biopsy from the fifth. The allografts were in place from 44 to 80 months; three patients were treated with hemodialysis before the diagnosis of acquired cystic disease, whereas two received peritoneal dialysis. Three of the four patients evaluated had cysts in the native kidneys. Although papillary hyperplasia of lining epithelium was evident in four specimens, only one kidney was the site of neoplasms in the form of multiple small tubular adenomas. No malignant neoplasms were noted in this study or in the few similar previous ones; however, it is possible that chronically rejected transplanted kidneys may harbor neoplasms with the same malignant potential as those in acquired cystic disease in native kidneys.

Quantitative studies of tubular immune complex formation and clearance in rats

Tubular antibody deposition and clearance was quantitatively studied using affinity-purified rabbit antibodies to rat Tamm-Horsfall protein (TH), a surface membrane glycoprotein of the tubular cells of the thick ascending limb of the loop of Henle. Immune complexes are formed in situ at the base of these cells in rats injected with antisera to TH. The renal binding of I125-anti-TH was determined in pair label studies. Kidneys and other organs were removed from groups of rats for isotope counting at four hours to 14 days after an injection of I125-anti-TH and I131-normal rabbit IgG. The greatest total renal anti-TH binding after injection of 500 micrograms of anti-TH was observed at 24 hours in normal rats (18.55 +/- 1.6 micrograms). During the period of most rapid clearance (day 2 to day 7) the half life of renal anti-TH binding (84.2 hours) and the half life of anti-TH in the serum (68.5 hours) were shorter than that of IgG in the serum (117.8 hours). There was no substantial uptake of anti-TH by other organs. A close relationship between serum levels and renal uptake of anti-TH at 24 hours was also observed in rats given from 50 to 6000 micrograms of anti-TH; renal saturation was evident only at the highest dose. This close relationship was also present during the clearance phase in rats injected with 3700 micrograms of anti-TH; the half life of anti-TH was 96.2 hours in kidneys and 110 hours in serum while the half life of rabbit IgG in serum was 151.8 hours. Markedly increased renal uptake of anti-TH was observed in protein-uric rats with passive Heymann nephritis. In very proteinuric rats, 14.1% of the injected dose was bound to kidneys at 24 hours. In these rats, serum anti-TH levels decreased very rapidly to 4% of control serum levels by five days. Throughout the period of study, the serum levels of anti-TH determined by direct radiometric assay corresponded very closely to those obtained by enzyme-linked immunosorbent assay (ELISA). Urinary excretion was a major mechanism for the clearance of anti-TH in proteinuric rats; more than 10% of the injected I125-anti-TH was recovered intact (that is, protein bound) during the first day after injection. During the clearance phase for renal deposits, urinary clearance of anti-TH exceeded urinary clearance of IgG due to release of renal bound antibody into urine.(ABSTRACT TRUNCATED AT 400 WORDS)

Implications of recombinant erythropoietin therapy for renal transplantation

We previously reported on the efficiency by which endogenous erythropoietin production corrects anemia after successful renal transplantation. Recent clinical experience with recombinant human erythropoietin in renal failure has demonstrated major benefit in correcting anemia with few adverse consequences. This article reviews our experience to date with recombinant human erythropoietin use in transplant recipients and explores the impact of therapy for the dialysis population awaiting transplantation. The issues of ongoing need for pretransplant blood transfusion, presensitization, organ transplant demand, therapeutic use of human recombinant erythropoietin for chronic rejection, and impact of an expanding, high-quality transplant recipient pool are discussed in the context of the recombinant erythropoietin era.

Serum erythropoietin levels after renal transplantation

We measured serum erythropoietin levels serially in 31 renal-transplant recipients treated with cyclosporine, using the recently developed recombinant human erythropoietin-based radioimmunoassay. The mean (+/- SEM) serum erythropoietin concentration in these patients before transplantation (14 +/- 2 U per liter) was similar to that in normal subjects who did not have anemia. A transient postoperative 9-fold increase (range, 0- to 74-fold) in the serum erythropoietin levels was followed by a smaller (3-fold) and sustained (28 +/- 3 days) second elevation. The initial increase occurred in the absence of graft function and was not accompanied by an erythropoietic response, whereas the second increase was associated with graft recovery and the complete resolution of the anemia. Serum erythropoietin levels returned to normal as the hematocrit rose above 0.32. Thereafter, the hematocrit continued to rise toward normal, while the serum erythropoietin levels remained normal. The patients in whom erythrocytosis or iron-deficiency anemia developed had persistently elevated serum erythropoietin levels. We conclude that in patients who have undergone renal transplantation, slight increases in endogenous erythropoietin levels induce erythropoiesis to the same extent as do large doses of exogenous erythropoietin in patients with uremia. Moreover, once initiated, erythropoiesis in renal-transplant recipients may be sustained by normal serum erythropoietin levels. These results suggest that the restoration of renal function improves the erythropoietic response to erythropoietin.

Erythropoietin in renal transplant recipients: studies based on recombinant human erythropoietin radioimmunoassay

In posttransplant patients, modest increases in endogenous EPO induce erythropoiesis similar to that observed in uremic patients who are given large doses of exogenous rHuEPO that generate vastly higher circulating EPO levels. Moreover, once it is initiated, erythropoiesis may be sustained by normal levels of EPO. These observations raise the possibility that the restoration of renal function may alter the EPO-erythropoiesis response pattern. It is also possible that the resolution of uremic anemia is dependent on factors in addition to the level of circulating EPO.

Infection patterns in cyclosporine-treated cadaveric renal transplant patients

Immunosuppression with Cs regimens has not significantly altered infection patterns relative to earlier modalities. However, reports of increased infection, especially with CMV/PCC, are not borne out in our experience both in numbers and timing of infections. Patients on low-dose Cs immunosuppression do continue to acquire infectious complications but, in general, rarely will lose their grafts or lives.

Cadaveric renal transplantation: surgical results and expectations in the cyclosporine era

During a 36-month period 100 patients received 104 cadaveric renal transplants with cyclosporine-based immunosuppression. Of the patients 26 required 31 additional operations. Of the 19 secondary operations performed 1 month after transplantation 18 were emergency in nature, whereas beyond this period the majority of the procedures were elective. Both deaths in this series were related to the operation. Only 1 graft loss was directly attributed to a secondary operation. The patient undergoing cadaveric renal transplantation is at significant risk (25 per cent) of requiring at least 1 additional operation. However, despite this high probability of reoperation, graft loss and patient death after such procedures should be rare.

Immunopathologic features of de novo membranous nephropathy in renal allografts

De novo membranous nephropathy (MN) is now one of the most common forms of posttransplant glomerular disease, second only to allograft glomerulopathy. We investigated several immunopathologic and physicochemical properties of the immune complex (IC) or IC components displayed in the sera of patients with de novo MN. The parameters studied included detection of small (9S) preformed IC by monoclonal rheumatoid factor, determination of IC isoelectric point by chromatofocusing, detection of cationic IgG spectrotypes (pI 8.0-9.2), and demonstration of brush border or tubular epithelial/interstitial antibodies in the sera by indirect immunofluorescence. Of 7 de novo MN sera, 5 demonstrated the presence of each of these four immunopathologic features, whereas normal transplant patients, transplant recipients with recurrent focal sclerosis (FSGN), and those with chronic rejection did not display such features. Sera of patients with untreated idiopathic MN revealed immunochemical properties of IC that were similar to those seen in circulating IC of de novo MN. These studies suggest that a strongly nephritogenic internal milieu exists in transplant recipients with de novo MN. Our data indicate that unique immunochemical properties of IC or their components may predispose to subepithelial immune deposit formation and should provide new insights into the pathogenesis of idiopathic human MN.

Declining incidence of wound infection in cadaveric renal transplant recipient

Over a five-year period 100 cadaveric renal transplants were performed. In 91 of these recipients, a prophylactic parenteral antibiotic (cefoperazone) was administered and closed wound drainage was used. Of these 91 patients, 33 received azathioprine/prednisone immunosuppression, whereas cyclosporine/prednisone with or without azathioprine was used in the remaining 58. The incidence of wound infections was significantly reduced from 12 per cent (4/33) in the azathioprine group to 1.7 per cent (1/58) in the cyclosporine group (p less than 0.01). When conventional immunosuppression (azathioprine/prednisone) is employed in renal transplantation, triple antibiotic prophylaxis that includes an aminoglycoside is most effective in preventing wound infections. A single non-nephrotoxic antibiotic, cefoperazone, offers similar protection in the cyclosporine/prednisone-treated renal transplant recipient.

The current role of pre-transplant blood transfusions and tissue typing in cadaveric renal transplantation

In a retrospective analysis of 74 consecutive cadaveric renal transplants performed at our center during a 38-month period we assessed the influence of random blood transfusions and tissue matching on graft and patient survival. All patients received cyclosporine and low dose prednisone with or without azathioprine as immunosuppressive therapy. Actual patient survival was 100 per cent at 1 year and actuarial 1-year graft survival was 82 per cent. Random blood transfusions and histocompatibility matching at the HLA-DR locus did not influence graft survival. Matching at 2 or more HLA-A and B loci was associated with a significant detrimental influence (p less than 0.05) on graft survival. We conclude that the use of cyclosporine-based immunosuppression overcomes much of the adverse effect of poor tissue matching and may obviate the need for random blood transfusions in cadaveric renal transplantation during the first year of engraftment.

Recurrent Henoch-Schönlein purpura following renal transplantation

A 20-year-old patient with Henoch-Schönlein purpura leading to end-stage renal failure received a living-related renal transplant. She was treated with conventional immunosuppressive therapy. Following a quiescent period of 18 months pretransplant, at 3 months after engraftment there was recurrence of purpuric lesions with subsequent abdominal pain and glomerulonephritis. Renal and skin biopsies confirmed the immunopathologic changes of Henoch-Schönlein purpura. This case represents the second report of an adult with multiorgan recurrence of Henoch-Schönlein purpura following transplantation.

In situ formation of subepithelial immune complexes in the rabbit glomerulus: requirement of a cationic antigen

In a previous study we examined the role of antigenic electrical charge as a factor influencing glomerular immune complex (IC) localization in the rabbit. From that study patterned after chronic serum sickness nephritis it was demonstrated that the administration of charge-modified cationic bovine serum albumin (BSA) of isoelectric point (pI) greater than or equal to 9.5 invariably resulted in heavy subepithelial deposits, whereas native BSA (anionic, pI 4.5) produced principally mesangial deposits. In order to investigate the mechanism by which the immune deposits formed, passive serum sickness was induced in New Zealand white rabbits by unilaterally perfusing kidneys of nonimmunized rabbits with five alternating cycles of saline, antigen and antibody, or immunized rabbits with saline and antigen alone. Localization of BSA and IgG along the glomerular basement membrane (GBM) occurred only after exposure to cationic BSA and antibody; nonimmunized animals perfused with cationic BSA and antibody to cationic BSA uniformly developed generalized, diffuse nearly linear deposits of IgG and BSA along the GBM. Similar deposits, which became progressively more granular after exposure to circulating antibody, were seen after the perfusion of cationic BSA alone into animals actively immunized with cationic or native BSA. Ultrastructural examination showed effacement of foot processes and isolated, irregular subepithelial and subendothelial deposits. Control perfusion employing alternating cycles of native BSA and anti-native BSA antibody, cationic BSA and normal sheep IgG, or native BSA alone in animals actively immunized with native or cationic BSA failed to develop glomerular IgG deposits. All control kidneys were normal on ultrastructural examination.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrical charge. Its role in the pathogenesis and prevention of experimental membranous nephropathy in the rabbit

Intravenous cationic bovine serum albumin (BSA, pI > 9.5) induces membranous nephropathy in immunized rabbits. In this study, unimmunized rabbits received intravenous injections of cationic (n = 3) or native (n = 3) or native (n = 3) BSA, followed by ex vivo isolated left renal perfusions with sheep anti-BSA antibody. Capillary wall deposits of IgG and C3 were seen exclusively in the group receiving cationic BSA, confirming an in situ pathogenesis for cationic, BSA-induced membranous nephropathy, and demonstrating the importance of a cationic antigen for its production. We then explored whether membranous nephropathy in this model is prevented by the concomitant injection of protamine sulfate, a filterable, relatively non-immunogenic polycation. An in vitro study demonstrated that protamine sulfate incubated with glomerular basement membrane (GBM) decreased the subsequent binding of radiolabeled cationic BSA (P < 0.05). In vivo, protamine sulfate was shown to bind to anionic sites in the glomerular capillary wall after intravenous injection.Groups of rabbits received 3 wk of daily intravenous injections of cationic BSA alone (n = 15) or cationic BSA and protamine (n = 18). After 2 wk of injection of cationic BSA alone, typical membranous nephropathy developed. Granular deposits of IgG and C3 were present along the GBM associated with subepithelial dense deposits, foot process effacement, and marked albuminuria. Protamine significantly reduced or prevented the formation of deposits (P < 0.001) and in6 of 18 protamine-treated animals, existing deposits decreased or disappeared between 2 and 3 wk of injection. Albuminuria was significantly reduced in protamine-treated animals with a mean of 124+/-55 mg/24 h compared to 632+/-150 mg/24 h in the control group receiving cationic BSA alone. No significant differences between the groups were noted in serum lev9lsof IgG, C3, anti-BSA antibody, or circulating immune complex size. Studies in additional animals (n = 5) given radiolabeled cationic BSA showed that protamine did not alter the clearance of cationic BSA from serum. Control experiments showed that protamine's beneficial effects were not related to its weak anticoagulant property or toits theoretical ability to deplete tissue histamine. The administration of heparin (n = 6) or diphenhydramine (n = 6) had no effect on the development of the epimembranous lesion compared to the group receiving cationic BSA alone. In addition, homogenized whole kidney histamine content was not significantly different in the group receiving cationic BSA alone compared to the group receiving cationic BSA and protamine. This work shows that a cationic BSA-induced glomerular lesion can be produced by a renal perfusion technique involving in situ complex formation and that this process requires a cationic antigen for its development. We believe that the demonstrated beneficial effects of protamine are due to its ability to bind to glomerular anionic sites, and that this electrostatic interaction results in inhibition for the further binding of the cationic antigen, thereby limiting the severity of glomerulonephritis in this model.

Induction of membranous nephropathy in rabbits by administration of an exogenous cationic antigen

We examined the role of antigenic electrical charge as a determinant of glomerular immune complex localization in the rabbit. Serum sickness nephritis was induced in groups of New Zealand white rabbits by daily 25-mg intravenous injections of bovine serum albumin (BSA) chemically modified to be cationic (pI > 9.5) or more anionic (pI, 3.5-4.6); an additional group received unmodified native BSA (pI, 4.5-5.1). Factors known to influence immune complex localization, e.g., molecular size of the administered antigen and resulting circulating immune complexes, immunogenicity, and disappearance time from the circulation were examined and found to be similar for both anionic and cationic BSA. Charge modification did increase the nonimmune clearance of cationic and anionic BSA compared with native BSA. Injected cationic BSA was shown in paired label experiments to bind directly to glomeruli compared with native BSA. The renal lesion produced by cationic BSA was markedly different from that found in rabbits given anionic or native BSA. Animals receiving cationic BSA uniformly developed generalized diffuse granular capillary wall deposits of IgG, C3, and BSA detected after 2 wk of injections and increasing until death at 6 wk. Qualitatively similar deposits were produced by the administration of low doses of cationic BSA of only 1 or 10 mg/d. In contrast, the injection of both anionic and native BSA resulted in mesangial deposits at 2 and 4 wk with capillary wall deposits appearing by 6 wk. Ultrastructural examination of animals receiving cationic BSA revealed pure, extensive formation of dense deposits along the lamina rara externa of the glomerular basement membrane whereas such deposits were absent or rare in animals injected with the anionic or native BSA. Albuminuria was significantly greater at 6 wk in the groups receiving cationic BSA with a mean of 280 mg/24 h compared with 53 mg/24 h in the combined groups injected with anionic or native BSA. Blood urea nitrogen values were similar in all groups at 2 and 4 wk but higher in the animals receiving cationic BSA at 6 wk. These experiments describe the reproducible induction of epimembranous immune deposits by administration of an exogenous cationic antigen. They suggest that antigenic charge can play an important role in the pathogenesis of membranous nephropathy by permitting direct glomerular binding of an antigen and predisposing to in situ immune complex formation.