Cytokines in human renal interstitial fibrosis. II. Intrinsic interleukin (IL)-1 synthesis and IL-1-dependent production of IL-6 and IL-8 by cultured kidney fibroblasts

We compared cytokine production from transformed human fibroblast cell lines derived from either a kidney with interstitial fibrosis or a normal kidney to that from primary human foreskin fibroblasts. Fibrosis-derived as well as normal renal fibroblasts, but not skin fibroblasts, spontaneously produced the chemokine, IL-8, and the growth promoting cytokine, IL-6. Spontaneous IL-8 and IL-6 synthesis by renal fibroblasts was dependent on the intrinsic release of IL-1, since blocking IL-1 receptors with IL-1 receptor antagonist (IL-1Ra) partially inhibited the constitutive production of these cytokines. Both kidney cell lines had detectable mRNA and protein for IL-1 alpha and IL-1 beta. Renal and skin fibroblasts stimulated by picomolar concentrations of exogenous IL-1 or TNF-alpha produced large amounts of IL-6 and IL-8, whereas nanomolar concentrations of basic fibroblast growth factor did not. Fibrosis-derived cells expressed less high affinity IL-1 receptors (600 receptors/cell; KD = 0.6 pM) compared to normal renal fibroblasts (1000 receptors/cell). However, fibrosis-derived renal fibroblasts produce three- to fourfold more IL-8 and IL-6 in response to picomolar concentrations of IL-1 beta compared to cells derived from a normal kidney. As this enhanced production is not due to increased numbers of IL-1 receptors, we speculate that post-receptor responsiveness to either endogenous or exogenous IL-1 is greater in fibrosis-derived renal fibroblasts than in cells from normal kidneys.

Cytokines in human renal interstitial fibrosis. I. Interleukin-1 is a paracrine growth factor for cultured fibrosis-derived kidney fibroblasts

We studied the role of interleukin-1 beta (IL-1 beta) and basic fibroblast growth factor (bFGF) in the proliferative response of transformed human renal interstitial fibroblast cell lines established from either a kidney with glomerulonephritis and interstitial fibrosis or a normal kidney in comparison to primary human foreskin fibroblasts. Growth of fibrosis-derived renal fibroblasts was inhibited in the presence of IL-1 receptor antagonist (IL-1Ra) by 35% (P < 0.005), suggesting that these cells produce IL-1 and possess IL-1 receptors as part of paracrine growth. In contrast, spontaneous proliferation of fibroblasts derived from a normal kidney or normal skin were not inhibited by IL-1Ra. In fibrosis-derived but not in normal renal cells, fibronectin synthesis was increased 2.2-fold (P < 0.01) in the presence of IL-1Ra. Addition of exogenous IL-1 beta or bFGF stimulated proliferation of skin fibroblasts. In contrast, growth of fibrosis-derived renal fibroblasts was stimulated by IL-1 beta and unchanged by bFGF. Growth of normal kidney fibroblasts was unaffected by bFGF and inhibited by IL-1 beta. We conclude that compared to normal fibroblasts, fibrosis-derived renal fibroblasts have a different cytokine-response profile, are IL-1-dependent, produce IL-1 as a paracrine growth factor and do not proliferate to bFGF, a classical fibroblast growth factor.

Prevention of glomerular hypertrophy and glomerulosclerosis in Milan normotensive rats by low-protein diet, but not by low-dose captopril treatment

Milan normotensive rats, which spontaneously develop marked proteinuria (PU) and glomerulosclerosis (GS), were either kept on a normal-protein diet, a normal-protein diet with additional low-dose captopril (CAP), which did not affect blood pressure, or on a low-protein diet. After 8 months PU (79 +/- 25 mg/day) GS (3 +/- 2%) and total glomerular volume (TGV; 27.9 +/- 2.9 mm3/kidney) were significantly lower (p < 0.05) in the low-protein diet group than in both the normal-protein group (PU 583 +/- 210 mg/day, GS 12 +/- 5%, TGV 34.6 +/- 8 mm3/kidney) and the low-CAP group (PU 611 +/- 224 mg/day, GS 16 +/- 6%, TGV 41.8 +/- 8.6 mm3/kidney). In conclusion, the development of glomerular hypertrophy and GS in Milan normotensive rats was reduced by the low-protein diet, but not by low-CAP treatment.

Pathogenetic and diagnostic aspects of dialysis-related amyloidosis

Dialysis-related amyloidosis (DRA) is a major cause of morbidity in end-stage renal disease patients. While retention of the precursor protein beta 2-microglobulin (beta 2-m) forms the essential basis for DRA, pathogenetic concepts include: qualitative and quantitative alterations in beta 2-m metabolism; local and systemic inflammatory changes, partly related to different treatment modes; general predisposing factors such as age at the onset of dialysis treatment. Clinical and radiological signs, as well as synovial thickening on sonography, suggest the presence of DRA, but histomorphological demonstration of beta 2m-amyloid is required for definitive proof. Scintigraphic imaging of DRA represents an additional, sensitive non-invasive diagnostic tool. Successful kidney transplantation stops the progression of DRA.

The role of plasma coating on the permeation of cytokine-inducing substances through dialyser membranes

We studied the effects of coating of dialyser membranes with plasma proteins on the permeation of bacteria-derived cytokine-inducing substances (CIS). An in vitro dialysis circuit using polysulphone (PS) or modified cellulose triacetate (mCT) dialysers was used. Precoating of the dialysers was performed by recirculation of 10% normal human plasma for 30 min in the blood compartment and subsequent rinse with pyrogen-free saline. Samples from the blood compartment were tested for induction of interleukin-1 alpha (IL-1 alpha), interleukin-1 beta (IL-1 beta) and tumour necrosis factor (TNF alpha) at various time points after challenging the dialysate with sterile culture supernatants from Pseudomonas aeruginosa. Contamination of the dialysate resulted in the appearance of CIS in the blood compartment of both polysuphone modified cellulose triacetate (IL-1 alpha: PS, time 0: 81 +/- 11 pg/ml, time 60 min: 4747 +/- 1822 pg/ml, P < 0.05; mCT, time 0: 235 +/- 141 pg/ml, time 60 min: 1632 +/- 531 pg/ml, P < 0.05). The plasma protein layer reduced the penetration of CIS significantly only for polysulphone (IL-1 alpha: PS, time 60: 4747 +/- 1822 versus 880 +/- 525 pg/ml, P < 0.05; modified cellulose triacetate, time 60 min: 1632 +/- 531 pg/ml versus 930 +/- 326 pg/ml). Samples from the blood compartment contained < 6 pg/ml LAL-reactive material at all time points. We conclude that plasma coating of polysulphone dialysers reduces the permeability for CIS derived from Pseudomonas, either by reducing the effective pore size or by adsorption of proteins that bind CIS.(ABSTRACT TRUNCATED AT 250 WORDS)

On the specificity of assays to detect circulating immunoglobulin A-fibronectin complexes: implications for the study of serologic phenomena in patients with immunoglobulin A nephropathy

Immunoglobulin A (IgA)-fibronectin complexes have been proposed as specific serologic markers of IgA nephropathy. They have been detected by the use of ELISA composed of an immobilized antifibronectin antibody (or albumin as a negative control) and an enzyme-conjugated anti-IgA antibody (antifibronectin capture assay). By the use of this type of assay, plasma samples from 32 normal controls, 38 IgA nephropathy patients, and 81 patients with other types of glomerulonephritis were analyzed. Extinction values in IgA nephropathy patients were higher (P = 0.06) than in patients with other glomerulonephritis types and significantly higher than in normals. Markedly lower values were obtained when the plates were coated with albumin. However, when the antifibronectin antibody was replaced by normal IgG or F(ab')2 fragments, almost identical extinctions were measured. The use of different antifibronectin antibodies, IgG, ELISA plates, or blocking regimens did not modify these results. Extinction values could not be suppressed by the addition of exogenous fibronectin. Similar extinctions were observed when plasma samples were replaced by physiologic concentrations of fibronectin-free IgA. Extinction values measured in the plasma samples correlated significantly with IgA concentrations in plasma as analyzed by nephelometry. A collagen binding assay, a second type of assay used to measure IgA-fibronectin complexes, also allowed the detection of fibronectin-free IgA, and again, extinctions measured in plasma could not be suppressed by exogenous fibronectin. In conclusion, both antifibronectin capture ELISA and collagen binding assays do not specifically detect only IgA-fibronectin complexes, but also total plasma IgA, which is frequently, but nonspecifically, elevated in IgA nephropathy.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma levels of tumor necrosis factor (TNF) and soluble TNF receptors in kidney transplant recipients

Tumor necrosis factor-alpha is elevated in plasma during kidney transplant rejection. However, the measurement and biological activity of TNF alpha is influenced by inhibitory soluble TNF receptors. We therefore determined plasma levels of TNF alpha and the 2 soluble TNF receptors, the 55-kDa TNF receptor (TNF-sR55) and the 75-kDa TNF receptor (TNF-sR75), by immunoassays in 25 patients before and daily after kidney transplantation. Plasma samples were retrospectively assigned to 3 groups: (1) patients with well-functioning grafts (n = 14); (2) patients with biopsy-proven graft rejections (n = 7 patients with 10 rejections); and (3) patients with episodes of CsA nephrotoxicity (n = 4 patients with 9 samples). On the day of biopsy-proven graft rejection, TNF alpha increased from 8.6 +/- 0.9 pg/ml to 14.8 +/- 3.5 pg/ml (P < 0.02), TNF-sR55 from 6.6 +/- 1.3 ng/ml to 9.0 +/- 1.2 ng/ml (NS), and TNF-sR75 from 10.3 +/- 1.0 ng/ml to 15.3 +/- 2.0 ng/ml (P < 0.01). During episodes of CsA toxicity, TNF alpha levels did not change, TNF-sR55 increased from 5.2 +/- 0.5 ng/ml to 10.5 +/- 0.5 ng/ml (P < 0.01), and TNF-sR75 increased from 10.2 +/- 0.8 ng/ml to 17.5 +/- 0.9 ng/ml (P < 0.01). There was a strong correlation between serum creatinine and plasma TNF-sR55 (r = 0.7, P < 0.001) and TNF-sR75 (r = 0.7, P < 0.001), but not with TNF alpha. Therefore, levels of TNF-sR55 and TNF-sR75 were corrected for serum creatinine. An index expressing TNF alpha over actively released soluble receptors (index = TNF alpha/(corr.TNF-sR55 + corr.TNF-sR75)) detected rejection episodes with a sensitivity of 70-80% and a specificity of 89%. We conclude that the measurement of plasma TNF alpha in combination with its soluble receptors is superior to isolated TNF alpha determinations in discriminating acute graft rejection from episodes of CsA toxicity in kidney transplant recipients.

[Lumbar spondylodiscitis caused by Salmonella enteritidis]

A 19-year-old boy developed paravertebral muscular pain in the lumbar region after an episode of extremely arduous sporting activity, with fever followed by meningism. The cerebrospinal fluid showed a reactive pleocytosis. Initially, no acute inflammatory changes were present on serum and blood analysis, although the erythrocyte sedimentation rate was moderately increased to 25/60 mm. Pyrexia of up to 38.5 degrees C developed 6 days after admission. Because Borrelia IgM and IgG titres were positive, the diagnosis was at first thought to be atypical borreliosis and the patient was treated with antibiotics. However, after a further episode of fever. Salmonella antibody titres, which had initially been normal, rose to 1: 3200 (Salmonella typhi O and H antigens) and 1: 12800 (Salmonella enteritidis, H antigen). At this stage, the erythrocyte sedimentation rate rose to 86/120 mm and the C-reactive protein to 77 mg/dl. The white cell count remained normal throughout. Blood cultures grew Salmonella enteritidis. Abnormalities on bone scintigraphy were confirmed by CT and MRI scans, showing spondylodiscitis of lumbar vertebrae 1 and 2 with limited osteolysis. The lesion resolved completely on 6 week's treatment with ciprofloxacin (200 mg twice a day intravenously) and conservative supportive treatment. Spondylodiscitis is an uncommon complication of salmonellosis and may occur long after the diarrhoea. Cross reactions with Borrelia flagellin antigens may lead to the wrong diagnosis being made.

Low-dose prednisolone/chlorambucil therapy in patients with severe membranous glomerulonephritis

Because of the high rate of spontaneous remission, treatment of membranous nephropathy with prednisolone and chlorambucil is still controversial. The aim of this study was to give this therapy only to those patients at risk of developing renal insufficiency and to test the efficacy of a low-dose therapeutic regimen. Seventeen patients with more than 10 g protein excretion per day (mean 16.9) and/or a deterioration in renal function (mean serum creatinine, 162 mumol/l) were included. Serum total protein, serum lipids, proteinuria, serum creatinine, and blood pressure were measured, along with the diuretic and antihypertensive medication. The observation time before the start of treatment was 27 +/- 27 months. Steroids were given during months 1, 3, and 5 (methylprednisolone 3 x 500 mg intravenously) prednisolone 0.5 mg/kgBW daily per os for 1 week, then tapered by 0.1 mg/kg BW/week for 1 month). Chlorambucil was given during months 2, 4, and 6 at a dose of 0.12 mg/kgBW daily. At the end of treatment proteinuria had significantly decreased (mean of all patients, 7.8 +/- 1.4 g/d) in all patients. Six months after the end of treatment proteinuria was significantly lower than at baseline in 14 of 17 patients. Hypoproteinemia and hyperlipidemia had improved; diuretic and antihypertensive medication were reduced. Elevated serum creatinine decreased in 7 of 9 patients (pretreatment, 227 +/- 39 mumol/l; 6 months, 176 +/- 28 mumol/l). Nonresponders with respect to serum creatinine responded with respect to proteinuria. Regarding adverse effects, two patients complained of dyspepsia while taking steroids; during chlorambucil treatment two patients experienced nausea and lack of appetite, and one developed leukopenia (1600/microliters).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of intermittent and continuous oral administration of calcitriol in dialysis patients: a randomized prospective trial

Intermittent bolus administration of calcitriol--i.e., 1,25-dihydroxycholecalciferol or 1,25-(OH)2D3--is highly efficacious in dialysis patients. In experimental studies, intermittent administration of calcitriol is superior to continuous administration in suppressing preproparathyroid hormone (PTH) mRNA and circulating PTH concentrations. In a randomized, prospective, open multicenter trial 45 dialysis patients with elevated 1,84-iPTH (> or = 20 pmol/l, normal 1-6 pmol/l) levels were randomly allocated to daily administration of 0.75 microgram calcitriol (continuous) or twice weekly administration (intermittent); the two protocols provided an identical total weekly doses of 5.25 micrograms calcitriol. Patients were dialyzed with a dialysate Ca concentration of 1.75 mmol/l and had oral CaCO3 or Ca acetate. 1,84-iPTH (immunoradiometric assay) and serum Ca and Pi levels were measured weekly. At the beginning of the study, the median 1,84-iPTH value was 37 pmol/l (range 20-115) in the intermittent versus 36 pmol/l (range 21-72) in the continuous calcitriol group. After 2 weeks, the median 1,84-iPTH level was 18.5 pmol/l (range 1.4-106) versus 18 pmol/l (range 1.2-48). After 12 weeks, 11 of 21 of the patients in the intermittent and 18 of 24 patients in the continuous group had reached the treatment goal, i.e., 1,84-iPTH < or = 10 pmol/l without hypercalcemia or hyperphosphatemia. There were seven episodes of hypercalcemia (> 2.7 mmol/l) in the intermittent versus two in the continuous group; the mean peak Ca level was 2.8 mmol/l (range 2.76-3.0) versus 2.9 mmol/l (range 2.74-3.06). There were 21 versus 17 episodes, respectively, of hyperphosphatemia (> 2.2 mmol/l).

Interstitial nephritis associated with 5-aminosalicylic acid

A patient with severe Crohn's disease was treated with 5-aminosalicylic acid (5-ASA). Following initiation of treatment, serum creatinine increased slowly from 105 to 530 mumol/l (creatinine clearance 16 ml/min). The diagnosis of an interstitial nephritis was made based on normal urinary findings and the renal biopsy histology of interstitial mononuclear infiltrates and normal glomeruli, 5-ASA was discontinued and serum creatinine decreased to 245 mumol/l (creatinine clearance 40 ml/min) during the following 3 months. Partial reversibility of renal failure following discontinuation of 5-ASA and the absence of other drugs possibly causing interstitial nephritis suggest a causal relationship between 5-ASA and interstitial nephritis.

The effect of ultrafiltered dialysate on the cellular content of interleukin-1 receptor antagonist in patients on chronic hemodialysis

We investigated the effect of dialysate ultrafiltration on the content of IL-1 receptor antagonist (IL-1Ra) in mononuclear cells (PBMC) as a marker of the inflammatory response. 11 patients on Cuprophan dialyzers were randomly assigned to treatment with standard bicarbonate dialysate first and then to ultrafiltered dialysate or the reverse order in a crossover design. In each treatment period (at least 4 weeks) weekly separations of PBMC were performed before the start of dialysis. Cellular content of IL-1Ra was determined in PBMC that were frozen immediately after separation; all values of IL-1Ra in each treatment period were averaged. The dialysate contained a median of 148 (range, 61-400) colony-forming units without dialysate filter; no bacterial growth was detected in ultrafiltered dialysate. The median endotoxin content was 80 pg/ml in nonfiltered dialysate; endotoxin was below 5 pg/ml in all ultrafiltered dialysate samples. Cellular content of IL-1Ra decreased in all but 1 patient with the use of ultrafiltered dialysate (mean +/- SEM: 1,467 +/- 113 pg/ml without dialysate filter vs. 1,166 +/- 104 pg/ml with filter, p = 0.016). The present study demonstrates that the bacterial contamination of the dialysate induces a systemic inflammatory response in hemodialysis patients.

[Cyclophosphamide bolus therapy in lupus nephritis]

A pilot study of 21 patients (17 women; 4 men; mean age 35 [18-59] years), randomized into two groups, was undertaken to test how many cycles of intravenous pulse cyclophosphamide administration were required in lupus nephritis to achieve remission. It was planned that patients randomized to group A should be treated for 3 months, those in group B for over 12 months. In the first cycle the cyclophosphamide dosage was 500 mg/m2, in the subsequent cycles, 4 weeks apart, it was raised by 250 mg/m2 to a maximum of 1,000 mg/m2, if the WBC count was over 2,000/microliters. Three women in group B gave up treatment prematurely after 5-8 cycles, because a remission had occurred. In group A only one patient went into remission after only three cycles. Of the total of 18 patients in both groups whose data could be evaluated, 15 achieved remission after an average of 7.3 cycles and a cumulative total cyclophosphamide dosage of 9.3 g. The disease progressed in two patients, one died. No recurrence has so far been observed after a follow-up period of 1-41 months. Three patients had infections and two had developed leukopenia as side effects. Pulse cyclophosphamide has thus been shown to be an effective treatment in lupus nephritis, but it must be continued for more than 3 months.

Effect of sodium acid pyrophosphate on ranitidine bioavailability and gastrointestinal transit time

During development of a ranitidine effervescent oral solution dosage form, a marked decrease was observed in the extent of ranitidine absorption relative to the conventional oral tablet. Two studies were conducted in healthy volunteers to confirm the involvement of an excipient, SAPP (sodium acid pyrophosphate), and the mechanism of interaction, altered gastrointestinal transit. The first study (n = 12) involved single-dose crossover comparisons of (A) 150 mg ranitidine with 1132 mg SAPP versus (B) 150 mg ranitidine and (C) 150 mg ranitidine with all the effervescent tablet excipients except SAPP versus (D) a 150-mg ranitidine effervescent tablet, all administered as oral solutions. Serum ranitidine AUC, Cmax, and tmax were compared using two one-sided t test 90% confidence intervals (CI). Comparing treatments A to B and D to C, all 90% CI were below the 80-120% range, indicating significantly less extensive ranitidine absorption (54% based on AUC) from the oral solutions containing SAPP. The second study (n = 12) was a single-dose crossover comparing 50 microCi 111 InCl solutions with and without 1132 mg SAPP. Gastrointestinal transit times, determined by scintigraphic imaging, were compared between treatments. Gastric emptying time was unchanged, but small intestinal transit time was decreased to 56% in the presence of SAPP. More rapid small intestinal transit associated with an excipient of a solution dosage form apparently resulted in a decreased extent of ranitidine absorption. This observation contradicts the conventional wisdom that oral solutions are unlikely to fall short of bioequivalence relative to solid oral formulations.

[Cyclophosphamide bolus therapy in lupus nephritis--status of the clinical study]

In order to establish a low-dose cumulative cyclophosphamide therapy for lupus nephritis, 21 patients were either randomized for at least 3 i.v. cyclophosphamide pulses until remission occurred or for 12 pulses. 18/21 patients developed a remission after an average of 7.3 pulses and a cumulative cyclophosphamide dose of 9.3 g. Side effects were only mild.

Gene expression of interleukin-1 beta during hemodialysis

It is still controversial whether the hemodialysis (HD) procedure is an inflammatory process in vivo. Therefore, we studied the gene expression of interleukin-1 beta (IL-1 beta) as a marker of inflammation in peripheral blood mononuclear cells (PBMC) of patients during HD by Northern blotting and polymerase chain reaction. Compared to PBMC separated pre-HD (1.0 densitometric units), the amount of IL-1 beta mRNA was increased in PBMC leaving the dialyzer (12.2 +/- 2 densitometric units, P < 0.01), but was not increased in PBMC re-entering the dialyzer from the systemic circulation (0.6 +/- 0.1 densitometric units) in all 12 patients studied. The maximal amount of IL-1 beta mRNA in PBMC was seen at five minutes after start of HD. There was a significant correlation between the increase in IL-1 beta mRNA and the increase in activated complement C5a (r = 0.71, P < 0.01). HD using less complement-activating membranes (hemophan, polysulfone, polyamide or polyacrylonitrile) resulted in no detectable IL-1 beta mRNA. Furthermore, a monoclonal antibody against human C5a reduced the increase in IL-1 beta mRNA by 83% (P < 0.05), indicating that C5a plays a major role for induction of IL-1 beta mRNA during HD. This study demonstrates that during HD with regenerated cellulose, gene expression for IL-1 beta takes place in PBMC.

[Clinical experiences with nocturnal intermittent peritoneal dialysis]

Nocturnal intermittent peritoneal dialysis (NIPD) was performed in 56 patients (37 men, 19 women; mean age 44 [18-77] years, 18 of them diabetics). The NIPD protocol laid down 6-10 automatic changes of 1.5-2.3 1 dialysate (mean glucose concentration: 1.9%) each night. Clinical and biochemical tests were performed three times, at least 4 weeks apart (the first one after 2 months of stable NIPD). 36 of the 52 patients under the age of 60 were working. Mean hospital stay (excluding catheter implantation and training) was 5 days yearly. Mean peritonitis rate was one episode every 54 months. Because of technical problems a change from peritoneal to haemodialysis became necessary in four patients. Clinical and biochemical findings were: creatinine 877 +/- 269 mumol/l, urea 20 +/- 5.2 mmol/l, potassium 4.5 +/- 0.6 mmol/l, calcium 2.3 +/- 0.2 mmol/l, phosphate 1.7 +/- 0.5 mmol/l, total protein 69 +/- 7 g/l, cholesterol 6.8 +/- 1.7 mmol/l, and triglycerides 2.6 +/- 1.4 mmol/l. These data show that NIPD is an effective method of dialysis which--in comparison with other techniques--has several advantages. Peritonitis and technical failure are rare.

Renal effects of atrial natriuretic peptide in cirrhotic rats with and without captopril pretreatment

Compared to healthy humans in most patients with cirrhosis and renal sodium and water retention, effects of atrial natriuretic peptide (ANP) on sodium and water excretion are reduced. It has been postulated that this impaired response to ANP is caused by renal vasoconstriction, induced by high levels of angiotensin II. To further investigate this issue, we studied renal hemodynamics (glomerular filtration rate, GFR, single nephron GFR, SNGFR, renal blood flow, RBF) and urinary sodium excretion (UNaV) in rats with CCl4-induced cirrhosis of the liver, before and during ANP infusion. The same parameters were determined in cirrhotic rats after a 4-day pretreatment with the angiotensin-converting enzyme (ACE) inhibitor captopril before and during ANP. Results were compared to those obtained in 2 control groups of healthy rats, one of them pretreated with captopril. Rats with cirrhosis had a significantly reduced GFR, SNGFR, RBF, UNaV and an elevated plasma renin activity compared to healthy controls. ANP caused a significant rise in UNaV (+198%) but no significant change of GFR, SNGFR and RBF in cirrhotic rats. Captopril-pretreated rats with cirrhosis had a significantly higher RBF (+26%) and 24-hour urinary sodium excretion (+52%) but no significant differences in GFR and SNGFR compared to cirrhotic rats without captopril pretreatment. Administration of ANP to cirrhotic rats pretreated with captopril resulted in a significant rise in GFR (+56%), SNGFR (+42%), RBF (+29%) and UNaV (+159%) compared to cirrhotic rats with ANP alone. In healthy rats, there was no additional effect of a combined therapy with captopril and ANP.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of low-molecular-weight dextran on proteolytic and nonproteolytic lysosomal enzymes in isolated segments of rat proximal tubule

Dextrans undergo glomerular filtration and are taken up by endocytosis into lysosomes of proximal tubule cells. We measured the activities of the intralysosomal proteolytic enzymes cathepsin B and L and the nonproteolytic acid phosphatase in microdissected segments of rat proximal tubules by means of fluorescent ultramicroassays. Cathepsin activities were increased following dextran injection in a dose-dependent manner. Cathepsin stimulation was not dextran-specific since enhanced proximal albumin uptake also increased cathepsin activities. Acid phosphatase remained almost unchanged. We conclude that increased proximal tubule uptake of macromolecules is accompanied by a rather specific stimulation of proteolytic enzymes in the lysosomes. For proteins this constitutes an adequate response to increased protein uptake to maintain the steady state between uptake and catabolism of proteins in lysosomes. For the nondigestible dextran the cathepsin induction is an inadequate response. Since lysosomal cathepsins are involved in breakdown of intracellular proteins, it is conceivable that the increased activities reflect increased cellular autophagy leading to proximal tubule damage.