Genetic factors in focal segmental glomerulosclerosis

The association between angiotensin-converting enzyme insertion/deletion gene variant and risk of focal segmental glomerulosclerosis: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

The association of the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) gene polymorphism with the risk of focal segmental glomerulosclerosis (FSGS) is still controversial. A meta-analysis was performed to evaluate the association between ACE I/D gene polymorphism and FSGS susceptibility.

METHOD

We performed a predefined literature search and selection of eligible relevant studies to collect data from electronic databases.

RESULTS

In total, 12 articles were identified for the analysis of the association between ACE I/D gene polymorphism and FSGS risk. One report included an investigation in Arab and Jewish populations separately. Thus, there were seven reports in Asians, two in Caucasians, one in Africans, two in Arabs and one in Jews. In Asians, there was a markedly positive association between the D allele or DD genotype and FSGS susceptibility (p = 0.008; p = 0.002), and the II genotype may play a protective role against FSGS onset (p = 0.002). However, a link between ACE I/D gene polymorphism and FSGS risk was not found in Caucasians, Africans, Arabs or Jews (Caucasians: D: p = 0.11, DD: p = 0.19, II: p = 0.70; Africans: D: p = 0.40, DD: p = 0.49, II: p = 0.61; Arabs: D: p = 0.34, DD: p = 0.10, II: p = 0.42; Jews: D: p = 0.90, DD: p = 0.97, II: p = 0.83).

CONCLUSION

The D allele or DD homozygosity may become a significant genetic molecular marker for the onset of FSGS in Asians, but not for Caucasians, Africans, Arabs or Jews.

Effect of interleukin-6 receptor blockage on renal injury in apolipoprotein E-deficient mice

Hyperlipidemia has been demonstrated to be associated with renal disease, yet the mechanism of renal injury is still poorly understood. Inflammation that occurs with the hyperlipidemia has been considered to play an important role in development of glomerular injury. In the present study, we investigated the role of interleukin-6 (IL-6), a key inflammatory molecule, on renal injury in apolipoprotein E-deficient (ApoE(-/-)) mice with severe hypercholesterolemia. The 6-wk-old mice were fed a high-fat diet and administered weekly rat anti-IL-6 receptor monoclonal antibody (MR16-1), control rat IgG, or saline for a total of 4 wk. We examined histopathological changes in the kidney and urinary excretion of protein and albumin. Saline- and IgG-treated mice showed remarkable proteinuria at 10 wk of age, whereas MR16-1-treated mice exhibited significantly lower levels. Renal histopathology of saline- and IgG-treated mice revealed striking lipid deposits and foam cells in the glomerular tuft, juxtaglomerular area, and arteriolar wall along with range of mesangial cell proliferation and matrix expansion. Notably, the severity of lipid deposits and mesangial cell proliferation were significantly reduced in MR16-1-treated mice. Immunohistochemistry demonstrated that mesangial IL-6 expression was dramatically reduced in MR16-1-treated mice compared with IgG-treated mice. Blocking the IL-6 receptor prevented progression of proteinuria and renal lipid deposit, as well as the mesangial cell proliferation associated with severe hyperlipoproteinemia. These results clearly demonstrate that IL-6 plays an essential role in the pathogenesis of hyperlipidemia-induced glomerular injury in ApoE(-/-) mice and suggests the usefulness of anti-IL-6 receptor antibody in treatments for hyperlipidemia-induced organ damage.

Effects of glutamine supplementation on kidney of diabetic rat

Glutamine is the most important donor of NH(3) in kidney playing an important role in acid-base buffering system. Besides this effect, glutamine presents many other relevant functions in the whole body, such as a precursor of arginine in adult and neonates. In addition to these effects, some studies have shown that glutamine can potentiate renal disease. In the present study, the effect of short-term treatment (15 days) with glutamine on control and diabetic rats was investigated. Using biochemical, histological and molecular biology analysis from control and diabetic rats we verified that glutamine supplementation increase in pro-inflammatory interleukins (IL)-1beta and IL-6 content in renal cortex and induce alteration in glomerular characteristics. This study showed that short-term treatment with glutamine in association with increased glucose levels could cause important alterations in glomerular morphology that may result in fast progression of kidney failure.

Strain differences in morphometrical characteristics of rat kidneys

To clarify the strain differences in the morphology of the rat kidneys, we investigated the morphometrical characteristics of the kidneys of Slc:Wistar, Slc:SD, and F344/NSlc rats. The diameter of the renal corpuscles in female F344/N rats is smaller than that in female Wistar rats. Although sex differences (males>females) were shown in SD and F344/N rats, no effects of castration were detected in any of the groups. Strain-dependent differences in the percentage of renal corpuscles with a cuboidal parietal layer were found in both male and female groups. The highest percentage of them was noted in male Wistar rats. Effects of castration were observed in female Wistar and male F344/N rats, and the values after castration were significantly higher than those in the intact animals. As for the number of proximal convoluted tubular nuclei, no strain differences were detected in either the male or female groups. Although a sex difference was found in SD rats (female>male), no effects of castration were detected in any of the groups. In female F344/N rats, numerous numbers of PAS-positive granules, which were observed in the proximal convoluted and straight tubular epithelia, were noted. Orchiectomy induced an increase of these granules in male SD and F344/N rats, but ovariectomy showed no effects on them in any strains. This is the first study to clarify the strain differences in the morphological characteristics of the kidneys in ordinary rat strains.

Genes expressed by the kidney, but not by bone marrow-derived cells, underlie the genetic predisposition to progressive glomerulosclerosis after mesangial injury

Progressive renal failure is accompanied by uncontrolled accumulation of extracellular matrix in glomeruli and tubulointerstitium, eventually resulting in glomerulosclerosis. Although glomerulosclerosis occurs secondary to various renal diseases, the fact that not all patients develop progressive glomerulosclerosis suggests that genetic factors may underlie the tendency to progress, or not to progress. Identified were two Lewis rat substrains with small genetic differences but with considerable difference in resolution of glomerulonephritis after anti-Thy-1 administration. In the Lewis/Møllegard rat strain, anti-Thy-1 glomerulonephritis spontaneously resolves within 4 wk. In contrast, Lewis/Maastricht rats develop progressive glomerulosclerosis after induction of this disease. The involvement of bone marrow-derived cells and kidney cells in the development of glomerulosclerosis was determined. In the first study, exchange of bone marrow between these substrains did not affect the course of anti-Thy-1 nephritis. Lewis/Møllegard rats recovered rapidly, but Lewis/Maastricht rats showed progressive disease regardless of the genotype of the bone marrow they received. In the second study, kidneys were exchanged between the substrains. After transplantation, anti-Thy-1 nephritis was induced and glomerular damage assessed at day 21. Severe damage was observed in Lewis/Maastricht glomeruli independent of whether the kidney had been transplanted or not. Similarly, Lewis/Møllegard glomeruli, whether transplanted or not, revealed no residual histopathologic abnormalities. The inherited differences between the two substrains with regard to their insusceptibility to develop progressive glomerulosclerosis after mesangial injury are governed by genes expressed by the kidney, but not by bone marrow-derived cells.

X-linked locus associated with hypertensive renal disease susceptibility in Dahl rats

OBJECTIVE

There is increasing evidence that genetic factors contribute to renal disease susceptibility associated with essential hypertension. To what extent these genetic factors act independently of hypertension susceptibility remains undetermined. The present study was undertaken to assess the potential chromosome X influence on target organ renal disease in the Dahl rat model of salt-sensitive hypertension.

SUBJECTS AND METHODS

Dahl S, Dahl R, F1(RXS), F1(SXR) and F2(RXS) rat male populations were phenotyped for hypertensive renal disease by measuring the percent of incidence of the Grade IV Raij renal pathology score. Six chromosome X markers informative for our (RXS) intercross were analyzed in our F2 rat population (n = 105) for co-segregation with hypertensive renal disease and blood pressure characterized by radiotelemetry.

RESULTS

Comparison of the incidence of renal disease (histologically determined) between F1 reciprocal intercross male progenies reveals a significant chromosome X effect on renal disease [percent incidence of Grade IV Raij renal pathology score in F1 (R female S male) male rats = 2.75 +/- 0.66, and in F1 (S female R male) male rats = 0.67 +/- 0.42; = 0.02]. QTL analysis on an F2(RXS) male population phenotyped for renal disease susceptibility (percent incidence of Grade IV Raij renal pathology score) detects significant linkage to DXRat98 (likelihood ratio statistic = 9.4, P = 0.00223) on chromosome X, corroborating X-linkage of renal disease susceptibility in Dahl rats.

CONCLUSIONS

Our results demonstrate the existence of an X-linked locus associated with hypertensive renal disease susceptibility in Dahl rats. Furthermore, the chromosome X markers tested did not co-segregate with hypertension, indicating that the gene(s) on chromosome X influence renal disease susceptibility independent of blood pressure.

Proteinuria and glomerulosclerosis in the Sabra genetic rat model of salt susceptibility

In search of an experimental model that would simulate the association between proteinuria and salt sensitivity in humans, we studied protein excretion in the Sabra rat model of salt susceptibility. Monthly measurements of urinary protein excretion in animals fed standard rat chow revealed that normotensive salt-sensitive SBH/y developed proteinuria that averaged 65 +/- 7 mg/day (n = 10) at 9 mo, whereas proteinuria in normotensive salt-resistant SBN/y was 39 +/- 4 mg/day (n = 10) (P < 0.01). Histopathological evaluation revealed focal and segmental glomerulosclerosis (FSGS) lesions grade 2 in SBH/y and normal histology in SBN/y. To amplify the differences between the strains, uninephrectomy was performed. At 9 mo, proteinuria in SBH/y with one kidney (SBH/y-1K) was 195 +/- 12 mg/day (n = 10) and in SBN/y was 128 +/- 10 mg/day (n = 10) (P < 0.001); histopathology revealed FSGS grade 3 in SBH/y-1K and grade 1-2 in SBN/y-1K. To determine the effect of salt loading, animals were provided with 8% NaCl in chow, causing hypertension in SBH/y but not in SBN/y. Proteinuria markedly increased in both SBH/y with two kidneys (SBH/y-2K) and SBH/y-1K, but not in SBN/y; histopathology revealed FSGS grade 1-2 in SBH/y-2K, grade 2 in SBH/y-1K, no lesions in SBN/y-2K, and grade 0-1 in SBN/y-1K. We concluded that the SBH/y strain is more susceptible to develop proteinuria and glomerulosclerosis than SBN/y. In search for the genetic basis of this phenomenon, we investigated the role of candidate proteinuric gene loci. Consomic strains were constructed by introgressing chromosome 1 (which harbors the rf-1 and rf-2 proteinuric loci) or chromosome 17 (which harbors rf-5) from SBH/y onto the SBN/y genomic background. The resulting consomic strains developed marked proteinuria that was severalfold higher than in SBN/y-1K; histopathological evaluation, however, revealed FSGS lesions grade 1-2, similar to those found in SBN/y-1K and less severe than in SBH/y-1K. These results suggest a functional role of gene systems located on chromosomes 1 and 17 in inducing proteinuria in the salt-susceptible Sabra rat strain. These genetic loci do not appear to harbor major genes for glomerulosclerosis.

Increased genetic susceptibility to renal damage in the stroke-prone spontaneously hypertensive rat

BACKGROUND

The spontaneously hypertensive rat (SHR) develops much less renal damage than the stroke-prone strain of SHR (SHRsp) after salt-supplementation, and it has been proposed that these strains differ in their genetic susceptibility to renal damage. However, radiotelemetric BP measurements have shown that salt-supplementation results in more severe and accelerated hypertension in the SHRsp. Therefore, it is unclear whether the differences in renal damage are due to differences in BP exposure or true differences in intrinsic (genetic) renal susceptibility to hypertensive damage.

METHODS

Kidney cross transplantation was performed between the SHR and SHRsp strains in uninephrectomized recipients to allow an investigation of the susceptibility to renal damage in SHR and SHRsp kidneys maintained in the same host and exposed to the same BP profile and metabolic environment. Following transplantation, BP was radiotelemetrically monitored before and after an 8% NaCl diet given to accelerate hypertension and renal damage. Then the kidneys were removed and renal damage was assessed histologically.

RESULTS

In the SHR recipients, the SHRsp donor kidneys exhibited more hypertensive damage than the contralateral native SHR kidneys, but histologic evidence of mild cellular immunologic rejection also was observed that could have facilitated the increased renal damage. However, even in SHRsp recipients, the native SHRsp kidneys exhibited twice the damage seen in the contralateral transplanted SHR kidneys.

CONCLUSION

These data unequivocally demonstrate that the SHRsp kidneys are intrinsically more susceptible than the SHR kidneys to renal damage when exposed to exactly the same BP and metabolic environment.

Does captopril change oxidative stress in puromycin aminonucleoside nephropathy?

Puromycin aminonucleoside (PAN) nephropathy in rats has been induced by the intraperitoneal injections of PAN. One group of animals which received PAN has been treated simultaneously with captopril (angiotensine converting enzyme-ACE-inhibitor) with the aim to test whether continuing treatment with captopril along with PAN injections would be able to modulate the toxic effects of PAN. The third group of rats was given only captopril. Morphological changes in the kidney were evaluated by scanning electron microscopy that showed the loss of podocyte foot processes in the kidney of PAN treated animals but also in the kidney of captopril treated ones as well as in the animals treated with both drugs simultaneously. Reduced glutathione content, catalase, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), xanthine oxidase activities as well as lipid peroxides were investigated in rat blood and kidney. Captopril given alone produced a significant decrease of plasma lipid peroxides, but it did not show any significant effect on investigated antioxidative factor levels neither in blood nor in the kidney. PAN given alone produced a significant depletion of plasma lipid peroxides, kidney catalase and erythrocyte GSH-Px activity as well as a significant increase of plasma catalase and erythrocyte SOD activity. Treatment of animals with both drugs simultaneously resulted in a significant increase of erythrocyte SOD activity and a significant decrease of plasma lipid peroxides, erythrocyte GSH-Px and kidney SOD activities. Kidney xanthine oxidase activity showed a significant increase in both PAN and PAN plus captopril treated animals in comparison with the values of captopril treated rats. These data suggest that PAN changes the antioxidative factor pattern in rat blood and kidney. Contrary to our expectations that captopril may protect the toxic effects of PAN it only to a certain extent modifies these effects showing protective effect only on tissue catalase activity.

Very low-density lipoprotein stimulates the expression of monocyte chemoattractant protein-1 in mesangial cells

BACKGROUND

Elevated plasma levels of very low-density lipoprotein (VLDL) are associated with an increased risk for focal glomerulosclerosis, which is analogous to atherosclerosis. One feature of focal glomerulosclerosis is the presence of foam cells derived from the infiltration of circulating monocytes. Mesangial cells are able to express monocyte chemoattractant protein-1 (MCP-1). In this study, the ability of VLDL to stimulate MCP-1 expression in mesangial cells and consequent monocyte adhesion was investigated.

METHODS

For adhesion studies, mesangial cells isolated from Sprague-Dawley rats were treated with VLDL for six hours, followed by a one-hour incubation with Tamm-Horsfall protein-1 (THP-1) cells. Mesangial MCP-1 mRNA levels were determined by reverse transcription-polymerase chain reaction. MCP-1 protein was determined by solid-phase immunoassay.

RESULTS

VLDL (100 to 300 microg/mL) significantly enhanced the expression and secretion of MCP-1 (54 to 285 ng/well) in mesangial cells. Such an effect was accompanied by the increased adhesion of monocytes to mesangial cells and later the formation of foam cells from monocytes after ingesting excessive amounts of VLDL lipids. VLDL-induced MCP-1 expression and monocyte adhesion were blocked by a protein kinase C inhibitor (staurosporine), as well as a calcium channel blocker (diltiazem).

CONCLUSIONS

Our results demonstrate that elevated levels of VLDL, through the action of MCP-1, may contribute to the infiltration of monocytes into the mesangium and subsequent foam cell formation. Hence, VLDLs may play a role in the pathogenesis of focal glomerulosclerosis. One of the mechanisms of such effect may be mediated through the calcium-dependent protein kinase C pathway.

Overexpression of Frat1 in transgenic mice leads to glomerulosclerosis and nephrotic syndrome, and provides direct evidence for the involvement of Frat1 in lymphoma progression

The proto-oncogene Frat1 was originally identified as a common site of proviral insertion in transplanted tumors of Moloney murine leukemia virus (M-MuLV)-infected Emu-Pim1 transgenic mice. Contrary to most common insertion sites implicated in mouse T cell lymphomagenesis, retroviral insertional mutagenesis of Frat1 constitutes a relatively late event in M-MuLV-induced tumor development, suggesting that proviral activation of Frat1 contributes to progression of T cell lymphomas rather than their genesis. To substantiate this notion we have generated transgenic mice that overexpress Frat1 in various organs, including lymphoid tissues. Frat1 transgenic mice develop focal glomerulosclerosis and a nephrotic syndrome, but they do not exhibit an increased incidence of spontaneous lymphomas. Conversely, these mice are highly susceptible to M-MuLV-induced lymphomagenesis, and Frat1/Pim1 bitransgenic animals develop lymphomas with increased frequency compared to Pim1 transgenic littermates. These data support a role for Frat1 in tumor progression.

Genetic isolation of a chromosome 1 region affecting susceptibility to hypertension-induced renal damage in the spontaneously hypertensive rat

Linkage studies in the fawn-hooded hypertensive rat have suggested that genes influencing susceptibility to hypertension-associated renal failure may exist on rat chromosome 1q. To investigate this possibility in a widely used model of hypertension, the spontaneously hypertensive rat (SHR), we compared susceptibility to hypertension-induced renal damage between an SHR progenitor strain and an SHR congenic strain that is genetically identical except for a defined region of chromosome 1q. Backcross breeding with selection for the markers D1Mit3 and Igf2 on chromosome 1 was used to create the congenic strain (designated SHR.BN-D1Mit3/Igf2) that carries a 22 cM segment of chromosome 1 transferred from the normotensive Brown Norway rat onto the SHR background. Systolic blood pressure (by radiotelemetry) and urine protein excretion were measured in the SHR progenitor and congenic strains before and after the induction of accelerated hypertension by administration of DOCA-salt. At the same level of DOCA-salt hypertension, the SHR.BN-D1Mit3/Igf2 congenic strain showed significantly greater proteinuria and histologically assessed renal vascular and glomerular injury than the SHR progenitor strain. These findings demonstrate that a gene or genes that influence susceptibility to hypertension-induced renal damage have been trapped in the differential chromosome segment of the SHR.BN-D1Mit3/Igf2 congenic strain. This congenic strain represents an important new model for the fine mapping of gene(s) on chromosome 1 that affect susceptibility to hypertension-induced renal injury in the rat.

The diuretic indapamide increases bone mass and decreases bone resorption in spontaneously hypertensive rats supplemented with sodium

Clinical and epidemiological studies suggest that thiazide diuretics can prevent bone loss and decrease the incidence of hip fractures. However, the mechanism of the effect of diuretics on bone is not clearly established. Indapamide (IDP), a sulfonamide diuretic related to thiazides, is used to treat hypertension. Sixty spontaneously hypertensive rats (SHRs) were divided into four groups and treated with or without IDP (1.5 mg/kg/day) during 8 weeks in the presence or absence of a high sodium load (8% NaCl supplementation in the diet). Sodium and calcium excretions were increased in the rats receiving the high sodium load (SHR + 8% NaCl) comparatively with control rats (SHR). IDP decreased and increased, respectively, calcium and sodium excretions. Serum parathyroid hormone (PTH) was unchanged in any group. Bone density was measured at the femur, tibia, and vertebrae, and bone morphometry was performed at the metaphysis of the femur to evaluate bone architecture. Rats fed a high sodium diet had an average 5.5% decreased bone density at every site except the femoral diaphysis. The trabecular bone volume was also decreased (SHR + 8% NaCl vs. SHR, 11.99+/-0.78 vs. 17.51+/-1.5%, p < 0.05). An increase in trabecular separation suggested that these changes were due to increased bone resorption. In the SHR + 8% NaCl + IDP group, IDP increased bone density and trabecular bone volume (SHR + 8% NaCl + IDP vs. SHR + 8% NaCl, 16.52+/-1.04 vs. 11.99+/-0.78%, p < 0.05). Trabecular separation and pyridinoline/creatinine excretion (SHR + 8% NaCl + IDP vs. SHR + 8% NaCl, 136.39+/-9.62 vs. 195.18+/-22.34 nmol/mmol, p < 0.05) were also decreased by IDP. These results show that in rats receiving a high sodium diet, IDP can reverse sodium-induced bone loss and increased bone resorption independently of changes in serum PTH.

A locus for inherited focal segmental glomerulosclerosis maps to chromosome 19q13

We performed a genome-wide linkage analysis search for a genetic locus responsible for kidney dysfunction in a large family. This inherited condition, characterized by proteinuria, progressive renal insufficiency, and focal segmental glomerulosclerosis, follows autosomal dominant inheritance. We show with a high degree of certainty (maximum 2-point lod score 12.28) that the gene responsible for this condition is located on chromosome 19q13.

Genetic susceptibility to hypertension-induced renal damage in the rat. Evidence based on kidney-specific genome transfer

To test the hypothesis that genetic factors can determine susceptibility to hypertension-induced renal damage, we derived an experimental animal model in which two genetically different yet histocompatible kidneys are chronically and simultaneously exposed to the same blood pressure profile and metabolic environment within the same host. Kidneys from normotensive Brown Norway rats were transplanted into unilaterally nephrectomized spontaneously hypertensive rats (SHR-RT1.N strain) that harbor the major histocompatibility complex of the Brown Norway strain. 25 d after the induction of severe hypertension with deoxycorticosterone acetate and salt, proteinuria, impaired glomerular filtration rate, and extensive vascular and glomerular injury were observed in the Brown Norway donor kidneys, but not in the SHR-RT1.N kidneys. Control experiments demonstrated that the strain differences in kidney damage could not be attributed to effects of transplantation-induced renal injury, immunologic rejection phenomena, or preexisting strain differences in blood pressure. These studies (a) demonstrate that the kidney of the normotensive Brown Norway rat is inherently much more susceptible to hypertension-induced damage than is the kidney of the spontaneously hypertensive rat, and (b) establish the feasibility of using organ-specific genome transplants to map genes expressed in the kidney that determine susceptibility to hypertension-induced renal injury in the rat.

Familial focal segmental glomerulosclerosis: nine cases in four families and review of the literature

Idiopathic focal segmental glomerulosclerosis (FSGS) is a common cause of glomerular disease. Although previous case reports suggesting a familial form of the disease exist in the literature, its significance has not been emphasized. We report on our experience with nine cases in four families, as well as a review of the literature, and provide evidence that a familial form of FSGS might represent a distinct genotypic and phenotypic subset of idiopathic FSGS.

The pattern of glomerular disease in New Caledonia: preliminary findings

Two hundred and two renal biopsies from 181 patients in New Caledonia were classified into either primary glomerulonephritis or glomerulopathy associated with systemic disease. These were then compared with 670 similar biopsies from 634 in-patients at Sydney's Royal Prince Alfred Hospital (RPAH). The most prevalent primary glomerular disease among the New Caledonian cases was focal segmental glomerulosclerosis, compared with IgA disease among the RPAH cases. Mesangiocapillary glomerulonephritis, post-infectious glomerulonephritis and minimal lesion nephropathy were all relatively commoner among the New Caledonian biopsies, but the numbers were small. The most prevalent systemic glomerulopathy in the New Caledonian cases were amyloidosis. This was the least common among our RPAH group. Diabetes mellitus and lupus nephritis were also slightly more common in the New Caledonian group. Focal necrotizing/crescentic glomerulonephritis was unusual in the New Caledonian samples, while it was the most common systemic glomerulopathy among the RPAH group.

Status of patients who underwent uninephrectomy in adulthood more than 20 years ago

We investigated the status of patients without systemic diseases who had undergone uninephrectomy for unilateral renal diseases in adulthood more than 20 years ago at Tokyo Denryoku Hospital. There were 21 participants (mean age +/- SD, 58.6 +/- 8.0 years) who fulfilled these criteria. The average interval since nephrectomy was 27.9 +/- 6.2 years. The mean current creatinine clearance was 88.5 +/- 21.2 mL/min/1.73 m2, which is 92.9% of that in healthy age- and sex-matched controls with two kidneys. The 24-hour urine protein excretion in these patients was only slightly higher than in the controls (214 +/- 190 mg v 119 +/- 62 mg, P = NS). Age at nephrectomy, length of time with a single kidney, or sex had little effect on the remnant renal functions. There was a positive correlation between current mean arterial pressure and serum creatinine (r = 0.44, P < 0.05). Patients who developed hypertension after uninephrectomy had a family history of hypertension more frequently than those with normotension (86% v 29%, P < 0.05). We conclude that (1) renal function after compensatory hyperfiltration of more than 20 years due to uninephrectomy for unilateral renal diseases in adulthood is well maintained, although hypertension has a considerable effect on the renal functions, and that (2) family history of hypertension plays a key role in determining the incidence of hypertension even in the uninephrectomized patients.

Growth abnormalities in cultured mesangial cells from rats with spontaneous glomerulosclerosis

Age-related glomerulosclerosis (GS) occurs in normotensive rats of the Milan strain (MNS), but not in genetically-matched hypertensive animals (MHS). Altered mesangial cell (MC) proliferation and matrix expansion are common features of the glomerular scarring process. We evaluated proliferation and matrix protein synthesis of cultured MC from MNS and MHS animals aged 1 and 8 months, that is, before and after the occurrence of GS. [3H]-thymidine (TdR) incorporation into DNA of MC from MNS rats stimulated by 10% FBS serum increased with donor aging from 115 +/- 6.0 to 176 +/- 15, P < 0.01 (% cpm/well over quiescent controls +/- SEM). Under the same experimental conditions, cell counts changed from 101 +/- 4.0 to 146 +/- 5.0, P < 0.01 (% cells/well over quiescent controls). Additionally, cytosolic Ca2+ concentration ([Ca2+]i) rised from 115 +/- 19 to 220 +/- 32 nM and from 112 +/- 24 to 734 +/- 136 nM when fura-2-loaded cells from young and old MNS rats, respectively, were stimulated with 1% FBS. The rate of collagen production also increased with donor age, as well as collagen IV and laminin B1 mRNA expression. In contrast, in MC from MHS rats both DNA synthesis and cell replication rate declined as function of donor age. No differences in the [Ca2+]i responses to FBS were observed, nor collagen production changed with MHS rat senescence. We conclude that the age-associated decline of proliferative activity in MC from MHS animals could actually reflect a normal process of cell aging, possibly protecting from the occurrence of GS.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of hyperfiltration on long-term follow-up of glomerular filtration rate in male Wistar rats

It has been suggested that a prolonged course of hyperfiltration could lead to progressive deterioration of renal function. In order to test this hypothesis, the following protocol was applied to 60 male Wistar rats. At 12 weeks of life, the rats were submitted to a surgical procedure: sham operation (25 rats), unilateral nephrectomy (25 rats) or 3/4 nephrectomy (10 rats). The three groups were again divided into two subgroups: one with high-protein intake (36%) and one with a low-protein intake (12%). In order to avoid any additional traumatic procedure which could shorten the animal's life, the glomerular filtration rate (GFR) was measured without blood sampling, using a previously validated technique based on an image recorded by a gamma camera between the 9th and the 10th min after intravenous injection of 99m technetium diethylenetriaminepentaacetate (DPTA). The sum of both kidneys and bladder activity was expressed as a percentage of the injected dose. The test was performed before surgery and every month thereafter. Six weeks after surgery, the highest filtration rate was found in the rats with "two kidneys/high-protein diet", followed by the "two kidneys/low-protein diet", the "one kidney/high-protein diet", the "one kidney/low-protein diet" and the "1/2 kidney". The overall GFR in the one kidney/high-protein diet rat and in the 1/2 kidney rat was respectively 80% and 55% of the pre-operative values. Until 109 weeks of age, the survival rate was comparable in the five groups of rats.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of lipids in nephrosclerosis and glomerulosclerosis

Hyperlipidemia and lipoprotein abnormalities are often encountered in patients with nephrotic syndrome or chronic renal disease and also in those undergoing haemodialysis and with renal transplant. Even though the significance of lipid deposition in renal tissue and the role of lipoproteins in the pathogenesis of renal disease in man is unclear, experimental and clinical data indicate a possible damaging effect of a disturbed lipid metabolism on the kidney. In humans, glomerular lipid deposition is observed in genetic diseases such as Fabry's disease, lecithin:cholesterol acyltransferase activity (LCAT) deficiency and arteriohepatic dysplasia, and in diseases with acquired disturbance of lipid metabolism such as nephrotic syndrome and cholestatic liver disease. Studies on animals with lupus nephritis, aminonucleoside nephrosis, reduced renal mass, diabetes mellitus or systemic hypertension have shown that cholesterol can increase the incidence of glomerulosclerosis. As most of these studies have been performed in the rat, which has a different lipoprotein profile to that of man, these results should be carefully interpreted with regard to their relevance for humans. In vitro cell culture studies on human glomerular cells have given some preliminary insights into the cellular mechanisms of lipid induced glomerular damage. Apo E-containing lipoproteins, which are pathologically elevated in many renal diseases, are avidly taken up by human mesangial cells. These cells seem to play a central role in the initiation of glomerulosclerosis by inducing proliferation and production of excess extracellular matrix. Lipoproteins are able to stimulate DNA synthesis in these cells, and increase the synthesis of mitogens and extracellular matrix protein. The pathogenic role of oxidized lipoproteins has not yet been defined. Human mesangial cells do not seem to take up these modified lipoproteins. However, macrophages infiltrate glomeruli and may constitute the stimulus for the generation of minimally modified lipoproteins and their cellular uptake. The data from animal experiments suggest that treatment that corrects hyperlipidemia may have an ameliorative effect on renal function. Thus, there are strong indications that lipoproteins may play a critical role in mediating the development of glomerulosclerosis.

Cell-mediated immune injury in the kidney: acute nephritis induced in the rat by azobenzenearsonate

Cell-mediated immune mechanisms have long been suspected of playing an important role in the pathogenesis of various renal diseases. An animal model of active nephritis secondary to an exogenous antigen that requires antigen presentation to immune-competent T cells has not been developed. Consequently, the potential of kidney cells to serve as effective antigen presenting cells after an exposure to a therapeutic, biological, or environmental agent in the intact animal has not been documented. The present experiments were designed to demonstrate the capacity of the kidney to become the target for cell-mediated immune injury. A model system has been developed whereby a chemically reactive form of the hapten azobenzenearsonate is introduced directly into the left kidney of pre-immunized Brown Norway rats. Previous studies have shown that this form of the hapten requires active antigen presentation but no intracellular processing, since the reactive form of the hapten modifies directly surface expressed proteins. Delayed hypersensitivity was demonstrated in the actively immunized animals by standard lymphocyte stimulation index and by in vivo skin testing. Peak foot pad swelling of 220 +/- 13 x 10(-2) mm in response to the hapten was observed between days 11 and 14 as compared to < 10 x 10(-2) mm in the contralateral foot injected with vehicle alone and < 20 x 10(-2) mm in response to azobenzenearsonate injection in animals immunized with adjuvant alone. The exposure of the kidney to the hapten in the primed animal results in an active unilateral granulomatous nephritis with marked destruction of tubules and glomeruli. On average, 71.5 +/- 5.2% of the renal cortex is affected by the inflammatory process in the actively immunized animals, compared to only 8.1 +/- 3.8% in controls. The disease can be reproduced qualitatively by adoptive transfer of T cells but not by passive antibody administration to naive recipients. These studies demonstrate that intrinsic kidney cells can act as effective antigen presenting cells in the intact animal and that the kidney can become the target of a cell-mediated immune injury.

Impact of tuberculosis in children with idiopathic nephrotic syndrome

Forty black South African children (mean age 4.7 +/- 2.6 years) with idiopathic nephrotic syndrome due to focal glomerulosclerosis (FSGS) were evaluated. Tuberculosis (TB) was found in 37.5% of children with FSGS (FSGS-TB) compared with 6% of a comparable group with minimal lesion nephrotic syndrome. No significant differences were found in the initial mean serum albumin, cholesterol, triglyceride and creatinine levels in FSGS-TB compared with children with glomerulosclerosis but without TB (FSGS-nonTB). The mean serum levels of C4, IgA and IgM were increased by 30%, 25% and 23%, respectively in children with FSGS-TB compared with FSGS-nonTB. Initial estimated creatinine clearance was similar in the two groups, but after a mean follow-up of 2.4 years, the mean estimated creatinine clearance of children with FSGS-TB was significantly reduced by 46% from the initial value, but remained stable in the FSGS-nonTB group. FSGS-TB children also had significantly increased requirements for renal replacement therapy compared with children with FSGS-nonTB. We conclude that TB infection is commonly associated with FSGS in black South African children; this may have deleterious effects on renal function.

Oxidized low-density lipoprotein in experimental focal glomerulosclerosis

Oxidized low-density lipoproteins (Ox-LDL) have been shown to be involved in the pathogenesis of atherosclerosis. Because of the similarities between atherosclerosis and focal glomerulosclerosis, a study was performed to demonstrate whether Ox-LDL could be detected in the glomeruli in experimental FGS. FGS was induced in 12 rats on a 4% cholesterol-1% choline diet by seven injections of puromycin aminonucleoside over a 10 week period. Eight rats on a normal diet served as controls. Fourteen weeks after the start of the experiment all rats were sacrificed. The test animals showed marked hypercholesterolemia and proteinuria. About 20% of glomeruli in test animals showed FGS and variable amounts of glomerular lipid were demonstrated. Immunohistochemical staining using five specific monoclonal antibodies against various forms of Ox-LDL showed positive staining of a variable number of glomeruli in the test rats. The staining pattern appeared to be intracellular. Staining with ED1 showed significantly increased numbers of intraglomerular monocytes in the test rats (test vs. control 2.4 +/- 1.1 vs. 0.4 +/- 0.1 monocytes per glomerulus, P < 0.0001). Control animals showed no segmental sclerosis, no glomerular lipid, and no staining for Ox-LDL. Lipid analysis of isolated glomeruli showed increased cholesterol, increased arachidonic acid and decreased eicosapentaenoic acid in test animals compared to controls. The findings suggest a role for Ox-LDL in the pathogenesis of experimental FGS and support the hypothesis that FGS is analogous to atherosclerosis.

Functional and structural determinants of glomerulosclerosis in the fawn-hooded rat

The effect of uninephrectomy (UN) at 4 months of age was studied on several parameters involved in the development of glomerulosclerosis (GS) in male spontaneously hypertensive Fawn-Hooded rats. Protein excretion per animal was significantly more increased in UN rats at 2 months after operation compared to sham operated controls (202 +/- 104 vs. 88 +/- 37 mg 24 h-1, P = 0.005) and remained significantly higher throughout the rest of the observation period. At 11 months of age UN rats had a marked increase in the incidence of GS, 37 +/- 16% compared to 5 +/- 3% (P less than 0.001) in controls. No differences were observed in mean arterial blood pressure. Functional studies in separate groups of rats at 5 months of age showed an increase in single kidney glomerular filtration rate in UN rats (0.40 +/- 0.07 vs. 0.28 +/- 0.09 ml min-1 100 g, P = 0.006). Single kidney renal plasma flow and filtration fraction were not altered. Mean glomerular volume was increased 1 month after UN (1.86 +/- 0.25 vs. 1.39 +/- 0.25 x 10(6) microns 3, P = 0.003). Urinary noradrenaline excretion per animal (24-h) showed a high sympathic nervous tone in both sham and UN rats. Total urinary dopamine and kallikrein excretion per animal were not influenced by UN. These data indicate that after UN the development of GS in this rat strain is accelerated in association with compensatory hyperfiltration and glomerular volume expansion, which may play a role in the pathogenesis of GS.

Interactions of hypercholesterolemia and hypertension in initiation of glomerular injury

In the Dahl S rat (DS), salt induces systemic and glomerular capillary hypertension associated with progressive glomerulosclerosis, while Dahl R rats (DR) remain normotensive, without glomerular abnormalities. Studies in experimental models have suggested that hypercholesterolemia may play a role in the development of glomerulosclerosis; however, it is unclear whether hypercholesterolemia alone, in the absence of hypertension, can initiate injury. To answer this question we induced hypercholesterolemia in salt-supplemented DS (DSC) and DR (DRC) by feeding a high cholesterol (4%) chow. Control rats (DS, DR) received high-salt, normal cholesterol chow. After eight weeks, DS and DSC developed equivalent hypertension (161 +/- 3 vs. 153 +/- 3 mm Hg, respectively, P = NS), while DR and DRC remained normotensive (138 +/- 5 vs. 131 +/- 5 mm Hg, P = NS; P less than 0.05 vs. DS and DSC). Cholesterol fed rats developed marked and equivalent hypercholesterolemia compared to controls (DS vs. DSC, 71 +/- 3 vs. 289 +/- 91 mg/dl, P less than 0.05; DR vs. DRC, 52 +/- 2 vs. 327 +/- 54 mg/dl, P less than 0.05). Hypertensive rats (DS, DSC) developed worse proteinuria and glomerular injury than normotensive rats (DR, DRC), but hypercholesterolemia exacerbated proteinuria and glomerulosclerosis only in DSC and not in DRC. Proteinuria significantly correlated with serum cholesterol in hypertensive rats (DS, DSC, P less than 0.05), but not normotensive rats (DR, DRC, P = NS). Furthermore, DSC had increased renal vascular resistance compared to DS, while no differences were found between DRC and DR. Thus, in the Dahl rat, hypercholesterolemia alone does not initiate glomerular injury. In this model, hypercholesterolemia is a pathogenetic factor in glomerular injury only when it coexists with systemic hypertension.

Mesangial expression of intercellular adhesion molecule-1 in primary glomerulosclerosis

Frozen sections of renal biopsy specimens from eight patients with primary focal segmental glomerulosclerosis (FSGS) and 10 patients with membranous nephropathy (MN) were stained in immuno-peroxidase with the intercellular adhesion molecule-1 (ICAM-1) monoclonal antibody (MoAb), CL203.4. ICAM-1 was expressed by mesangial cells in six patients with FSGS. On the other hand, ICAM-1 was not detected in mesangial cells in patients with MN or in the non-affected portion of tumoral kidneys used to control normal renal expression of ICAM-1. De novo mesangial expression of ICAM-1 in FSGS suggests that sclerosis results from an inflammatory process, possibly associated with local release of cytokines.

Focal glomerulosclerosis in idiopathic membranous glomerulonephritis

The significance of the finding of focal glomerulosclerosis (FGS) in idiopathic membranous glomerulonephritis (MGN) is uncertain. Twenty-seven patients with mixed FGS and MGN (MGN-FGS) were compared to 25 patients with MGN alone (generally matched for age, sex and stage of glomerular lesion) with respect to pathology, presenting clinical and laboratory features, and course of disease. Biopsies from the MGN-FGS patients showed significantly more extensive tubulointerstitial disease (P less than 0.001) than did those with MGN alone. At the time of biopsy, the MGN-FGS group had a significantly higher proportion of patients with hypertension (P = 0.006) and microhematuria (P = 0.006), a marginally higher percentage of patients with the nephrotic syndrome (P = 0.051), and a greater mean 24-hour urinary protein excretion (P = 0.004). A similar proportion of patients in each group were treated with either prednisone alone or prednisone with an immunosuppressive. Forty-eight percent of MGN-FGS patients and 13% of the MGN patients developed established renal failure in the follow-up period (P = 0.008). The renal survival rate for the MGN-FGS group was significantly lower at 24 months (0.61 vs. 0.93, P less than 0.05), 60 months (0.48 vs. 0.88, P less than 0.025), and over the entire follow-up period (P less than 0.05). The results indicate that FGS in MGN is associated with a significantly poorer prognosis than MGN without this lesion.

Nephrotic proteinuria without hypoalbuminemia: clinical characteristics and response to angiotensin-converting enzyme inhibition

Although hypoalbuminemia is a fundamental characteristic of nephrotic syndrome (NS), there are many patients with massive proteinuria that do not develop hypoalbuminemia. We have studied the clinical and biochemical characteristics of 19 patients with persistent massive proteinuria (greater than 5 g/d) and normal serum albumin (group I) in comparison with 16 patients with similar proteinuria excretion, but persistent hypoalbuminemia (group II). Most of group I patients had diagnoses suggesting glomerular hyperfiltration (focal glomerulosclerosis [FGS] associated with vesicoureteral reflux [VUR], reduction of renal mass, proteinuria associated with obesity, sclerotic phase of idiopathic crescentic glomerulonephritis [GN] in contrast with those of group II, in which membranous GN was the most frequent diagnosis. We prospectively investigated differences in the antiproteinuric effect of captopril, an antiotensin-converting enzyme inhibitor (ACEI); after 6 months of treatment, proteinuria decreased clearly in group I (7.1 +/- 1.7 to 3.7 +/- 1.7 g/d; P less than 0.001), whereas no significant changes were observed in group II (8.1 +/- 2.4 to 8.8 +/- 4 g/d). Serum creatinine (Scr) remained stable during captopril treatment in group I, whereas three patients in group II showed a worsening of renal function.(ABSTRACT TRUNCATED AT 250 WORDS)

Do glomerular hemodynamic adaptations influence the progression of human renal disease?

Although experiments in the rat suggest that glomerular hemodynamic alterations following a reduction of renal mass may be implicated in the progression of chronic renal failure, we argue that the deleterious effects of similar adaptations in human renal disease are unproven. In the otherwise normal solitary kidney the supranormal glomerular filtration rate (GFR) remains stable over the longterm, and in early diabetic nephropathy which is also accompanied by hyperfiltration, renal deterioration cannot be dissociated from a rise in systemic blood pressure. In patients with miscellaneous renal diseases and a depressed basal GFR there is indirect evidence that hyperfiltration might occur in some of the remnant glomeruli. However, at present there is little conclusive evidence to indicate that therapies which might normalize glomerular hemodynamics, e.g., dietary protein restriction, have any effect on progression of renal disease, or that angiotensin converting-enzyme inhibitors, which lower glomerular capillary pressure, have any advantage over other antihypertensive agents which are equally efficacious in lowering systemic blood pressure.

Comparison of converting enzyme inhibitor and calcium channel blocker in hypertensive glomerular injury

The protective effect of converting enzyme inhibitors in experimental hypertensive glomerular injury is associated with decreased systemic arterial and glomerular capillary pressure. Although calcium channel blockers effectively lower systemic blood pressure, their effect on glomerular capillary pressure and on hypertensive glomerular injury is uncertain. We compared equihypotensive treatment with the calcium antagonist TA 3090 or the converting enzyme inhibitor captopril in post-salt hypertensive Dahl salt-sensitive (DS) rats for up to 5 weeks after five sixths nephrectomy. Before the nephrectomy, all rats demonstrated hypertension (mean 177 mm Hg), proteinuria (mean 175 mg/day), and mild glomerulosclerosis (mean injury score 35). Rats treated with captopril or TA 3090 demonstrated a significant and equivalent decrease in systolic blood pressure compared with untreated rats at 2, 3, and 5 weeks after five sixths nephrectomy; however, only captopril reduced proteinuria. Final proteinuria was actually increased in rats treated with TA 3090 compared with untreated rats. Glomerular injury score was significantly decreased in captopril-treated compared with untreated rats at 2 weeks (33 +/- 9 versus 117 +/- 10, p less than 0.05) and 5 weeks (46 +/- 9 versus 94 +/- 24, p less than 0.05), whereas treatment with TA 3090 delayed but did not prevent progressive glomerular injury (2-week score 35 +/- 7, p less than 0.05 versus untreated; 5-week score 109 +/- 19, p = NS versus untreated). Thus, in hypertensive DS rats after subtotal nephrectomy, treatment with a converting enzyme inhibitor reduced systemic blood pressure, proteinuria, and glomerulosclerosis. However, equihypotensive treatment with a calcium channel blocker did not reduce proteinuria and delayed but did not prevent glomerulosclerosis. Thus, in the rat similar reductions in systemic blood pressure with these two classes of agents have disparate effects on the progression of chronic renal failure.

Role of enhanced glomerular synthesis of thromboxane A2 in progressive kidney disease

Normotensive rats of the Milan strain (MNS) spontaneously develop focal glomerulosclerosis. In order to explore the contribution of glomerular thromboxane (TX) A2 synthesis to the development of the disease, we have characterized the time course of renal functional and biochemical changes, and their modification by long-term treatment with a TX-synthase inhibitor. Oral administration (150 mg.kg-1 from 1 to 14 months of age) of FCE 22178 suppressed enhanced glomerular TXB2 production at all experimental times (mean inhibition 80%) and proteinuria (varying between 27.1 and 73.0%) while preserving renal blood flow and glomerular filtration rate. These effects of TX-synthase inhibition were seen in the absence of any statistically significant changes in systemic blood pressure. Moreover, FCE 22178 had no antihypertensive effects in hypertensive rats of the Milan strain (MHS) nor in spontaneously hypertensive rats (SHR). Treatment also prevented the age-related hypoalbuminemia and hyperlipidemia observed in control MNS and significantly (P less than 0.01) reduced glomerular histologic damage, as demonstrated by light microscopy studies and measurement of sclerotic area. We conclude that: 1) MNS rats provide an animal model of long-lasting proteinuria characterized by an age-related increase in glomerular TXB2 production paralleled by progressive loss of renal structural integrity and function and by a secondary dyslipidemia; 2) pharmacological inhibition of glomerular TX-synthase attenuates the structural as well as the functional expression of kidney disease, without a primary effect on systemic blood pressure. These data are suggestive of an important modulating role of TXA2 in the progression of MNS renal disease.

Absence of glomerular injury or nephron loss in a normotensive rat remnant kidney model

Severe reduction in renal mass (greater than 50%) in the rat uniformly results in progressive glomerular injury and loss of remnant nephrons postulated to be due to increases in glomerular function (hyperfiltration) and/or size (hypertrophy). Reduction in renal mass in the rat also leads to the development of systemic and/or glomerular hypertension. To examine the independent contributions of systemic hypertension and glomerular hyperfiltration and/or hypertrophy to progressive glomerular injury, a normotensive rat remnant kidney model was developed in the Wistar-Kyoto (WKY) strain. Of the 34 WKY rats that underwent 5/6 nephrectomy, 25 remained normotensive and without evidence of morphologic glomerular injury and/or nephron loss for up to 14 to 16 weeks, despite glomerular hyperfiltration and hypertrophy comparable to that previously observed in other rat strains. Micropuncture studies at approximately six weeks after reduction in renal mass demonstrated markedly increased SNGFR in remnant nephrons of normotensive rats as compared to controls (66 +/- 7 vs. 25 +/- 4 nl/min, P less than 0.01), but glomerular capillary pressures (PGC) estimated from stop flow pressures were only slightly increased (52.7 +/- 1 vs. 47.3 +/- 1 mm Hg, P less than 0.01). These data indicate that compensatory glomerular hyperfiltration and hypertrophy after 5/6 nephrectomy may not lead to progressive glomerular injury provided hypertension does not develop. These data further suggest that in the absence of systemic hypertension, increases in PGC required for adaptive hyperfiltration, may not be sufficient to initiate progressive glomerular injury and nephron loss.

Relationship of glomerular hypertrophy and sclerosis: studies in SV40 transgenic mice

We previously described the development of glomerulosclerosis in mice transgenic for large T-antigen, a gene whose in vitro expression markedly increases proliferation of cultured cells. In the current study we sought to determine the effect of unilateral nephrectomy on these sclerosis-prone animals which have a genetically defined potential for increased renal growth. In comparison with sham nephrectomy animals, nephrectomized transgenic female mice had significantly larger kidneys, larger glomeruli (5886 mu2 npx vs. 3796 mu2 sham), more cells per glomerulus and more severe glomerulosclerosis. Nephrectomized transgenic male animals had variable increases in kidney size, no significant increase in glomerular size (4750 mu2 npx vs. 4502 mu2 sham) or cellularity, and no worsening of glomerulosclerosis. In non-transgenic female animals nephrectomy induced an increase in kidney size but not in glomerular size (2640 mu2 npx vs. 2625 mu2 sham) and failed to induce glomerular lesions. A close correlation (r = 0.91) was found between glomerular size and severity of glomerulosclerosis in these animals. This finding supports the hypothesis that a pathophysiologic link exists between glomerular enlargement and glomerulosclerosis. We also found that increases in total kidney size and glomerular size did not consistently parallel each other, that is, renal hypertrophy may occur without an increase in glomerular size. This finding suggests that total kidney growth and glomerular growth may be independently regulated or may have different thresholds for activation following unilateral nephrectomy.

Different types of segmental sclerosing glomerular lesions in six experimental models of proteinuria

From 133 to 615 glomeruli were examined in sections of kidneys from each of 60 animals, representing six rodent models of proteinuria. Particular attention was paid to the position of segmental lesions. Lewis rats given sheep anti-rat glomerular basement membrane antibodies had lesions almost exclusively at the glomerulo-tubular junction. Wistar rats on a diet of 24 per cent casein or with subtotal nephrectomy and a diet of 24 per cent soya had lesions mainly at the hilum. Wistar rats given bovine serum albumin had global lesions but virtually no segmental lesions. Wistar rats given puromycin aminonucleoside had lesions at the glomerulo-tubular junction and global mesangial abnormalities shortly after the treatment but later developed segmental lesions at all parts of the glomerulus. Untreated BUF/Mna rats had lesions at the glomerulo-tubular junction early in life but later had lesions at all parts of the glomerulus. Untreated NZB/NZW hybrid mice had various types of glomerulonephritis and also had lesions at the glomerulo-tubular junction. These findings showed that (1) segmental lesions at the glomerulo-tubular junction, or glomerular tip, occur in experimental animals, a fact not previously reported, and these tip changes are a common feature in several different models of proteinuria; (2) hilar segmental lesions are seen in conditions with hyperfiltration of protein; and (3) segmental lesions at various parts of the glomerulus are seen in some models of proteinuria and probably indicate late effects of random toxic damage to the glomerulus. Thus, there are at least three different types of segmental glomerular lesions in experimental animals--tip, hilar, and random--with different morphology and pathogenesis. It is likely that these findings can be extended to human renal diseases with segmental glomerular lesions. This will help to clarify the controversial and unsatisfactory term focal segmental glomerulosclerosis.

Effects of dietary protein content in streptozotocin-diabetic rats

We evaluated the influence of increased dietary protein intake on glomerular structure and function in Lewis rats made diabetic with streptozotocin. We found that diabetic animals on a 20% or 50% protein diet ate approximately 50% more protein and excreted about 50% more urinary urea nitrogen than did their respective similarly-fed nondiabetic controls. The 50% protein diet was associated with higher glomerular filtration rates (GFR) and renal blood flows (RBF) at two months in both diabetic and control animals compared to their respective controls on the lower protein diet. However, GFR and RBF were not significantly higher in the diabetic animals on the 50% protein diet in the controls on the 20% diet and were slightly, albeit not significantly lower than controls on the 50% diet. Glomerular capillary pressure (PGC) tended to be lower in the diabetic compared to their respective controls, while the high protein diet was associated with higher PGC in diabetic and nondiabetic animals. The PGC in the 50% diabetic rats was not different from the PGC in the nondiabetic rats. Urinary albumin excretion (UAE) rate was greater in the diabetic than in the nondiabetic animals. UAE was greatest in the high protein diabetic animals at six months. Glomerular basement membrane thickness after six months of diabetes was increased essentially equally in both normal and high-protein fed diabetic groups and was largely uninfluenced by diet in the controls. Fractional mesangial volume was increased and relative filtration surface was decreased only in the 50%-protein diet diabetic rats at six months. Thus, high protein diet was associated with increased fractional mesangial volume in diabetic rats, but this could not be explained by increased glomerular capillary flows or pressures. The mechanism of acceleration of mesangial expansion by high protein diet in diabetic animals was not elucidated by these studies.

Mechanisms of hypertensive glomerular injury

Systemic hypertension complicates the course of most patients with chronic renal failure and accelerates the progression of experimental and clinical glomerular disease. Based on recent experimental studies, it is suggested that at similar levels of systemic hypertension, glomerular injury only develops when pre-glomerular resistances are ineffective, thus allowing the development of glomerular hypertension. The mechanisms by which the hemodynamic stress of elevated intracapillary flows and pressures leads to progressive glomerular damage, particularly to the development of focal glomerulosclerosis is currently unknown. Endothelial cell injury, increased mesangial traffic or trapping of macromolecules and epithelial cell injury, or a combination, appear to occur early, followed by in situ inflammatory and microthrombotic mechanisms. This may explain why various therapeutic approaches, whether dietary or pharmacologic, can have salutory effects despite their diverse mechanisms of action.

Possible genetic predisposition to idiopathic focal segmental glomerulosclerosis

HLA-A, B, and DR antigen frequencies were studied in a group of 57 patients to determine possible inborn susceptibility to idiopathic focal segmental glomerulosclerosis (FSGS). There were 34 white patients and 23 black patients, most of whom had nephrotic syndrome and later developed renal failure. HLA-DR4 was significantly increased in both patient groups when compared with their respective control groups. This association has not been previously reported. Of note, the association with DR4 was most striking in patients with adult onset disease (in blacks, relative risk equals 5.2; in whites, relative risk equals 5.8). No other antigen was increased in both patient groups but HLA-A28 was increased in blacks. These data support the notion of genetic predisposition to focal segmental glomerulosclerosis in two different ethnic groups.

Differences in puromycin aminonucleoside nephrosis in two rat strains

Administration of puromycin aminonucleoside (PAN) to Wistar rats induces proteinuria and enhanced mesangial deposition of circulating macromolecules. After proteinuria of longer duration focal and segmental glomerular hyalinosis and sclerosis (FSGHS) develops. The present report analyzes these aspects of PAN nephrosis in PVG/c rats, a strain previously shown to be remarkably resistant to proteinuria and FSGHS with aging or after uninephrectomy. In Wistar rats multiple injections of PAN during five months resulted in sustained severe proteinuria and FSGHS lesions in 8.1 +/- 1.0% (mean +/- 1 SEM) of their glomeruli (N = 6). In PVG/c rats a 1.3-fold higher dose of PAN was needed to induce chronic proteinuria similar to the Wistar rats. After five months 3.3 +/- 0.9% of their glomeruli showed FSGHS (N = 6, P less than 0.01) and the glomerular lesions were considerably less advanced. In acute PAN nephrosis induced by a single intravenous injection of PAN the mesangium of Wistar rats contained large amounts of lipid in contrast to a few small mesangial lipid droplets in nephrotic PVG/c rats. After injection of colloidal carbon in nephrotic PVG/c rats no enhanced carbon accumulation was found in the mesangium when compared to nonproteinuric controls. This result clearly differs from the increased mesangial sequestration of circulating material in nephrotic Wistar, and most other rat strains. The unchanged mesangial traficking of macromolecules in nephrotic PVG/c rats and the low incidence of FSGHS lesions in the presence of sustained glomerular proteinuria may reflect a relative resistance to PAN-induced glomerular damage in this particular rat strain.

Converting enzyme inhibition and progressive glomerulosclerosis in the rat

The effect of converting enzyme inhibition (CEI) by captopril (CAP, 500 mg/liter drinking water) on the development and progression of glomerulosclerosis (GS) was studied in six groups of male uninephrectomized (UN) Wistar rats. In group A, treated with CAP for four to five weeks after UN, a reduction in systolic blood pressure (SBP), filtration fraction and glomerular volumes was found as compared to control group B. Long-term treatment with CAP for eight months after UN (group C) resulted in lowering of SBP with 30 mm Hg, a low level of proteinuria and low incidence of GS (0 to 1.5%) as compared to control rats (group D), with SBP of 131 +/- 4 mm Hg, proteinuria up to 103 to 509 mg/day and 9.1 to 29.7% GS at eight months after UN. Groups E and F were followed without therapy up to seven months after UN, at which time a high level of proteinuria was present. CAP therapy then started in group E, did not reduce SBP, proteinuria and GS at 11 months after UN relative to control group F. This study shows that early CEI prevents progressive proteinuria and GS in rats after UN and is associated with a reduction in SBP, filtration fraction and glomerular volume. Once high levels of proteinuria and GS have developed in rats after UN, CEI has no effect on SBP nor on the progression of GS and proteinuria.

Glomerulosclerosis and renal cysts in mice transgenic for the early region of SV40

Considerable evidence indicates that genetic determinants play a major role in the pathogenesis of a variety of human and experimentally-induced renal diseases. There are, however, no firm data to indicate which genes or types of genes can induce or promote renal disease. The recently acquired ability to make specific alterations in the genetic background of an animal affords a unique opportunity to assess the effect(s) of a given gene on the structure and function of an organ of interest. Such modifications have been carried out in the creation of transgenic mice. We examined mice transgenic for the transforming gene encoding large T-antigen which is present in the early region of simian virus 40 (SV40). Renal lesions were present in most animals. While there was some heterogeneity in the type and severity of the renal lesions observed, a majority of the older mice displayed glomerulosclerosis and/or proliferative tubular lesions which in some were associated with multiple, large tubular cysts. The appearance of these lesions in mice transgenic for a transforming gene suggests that renal expression of a gene which controls cell proliferation may be associated with the development of glomerulosclerosis and renal cysts. These findings indicate a possible role for other transforming genes, or oncogenes, in the pathogenesis of glomerulosclerosis and cystic renal disease in humans and other animal models.

Epidemiology of idiopathic glomerular disease: a prospective study

In this study incidence rates of idiopathic glomerular disease in 1.5 X 10(6) Dutch adults between 16 and 65 years of age were determined, as well as the prevalence of these diseases in terms of indication for renal biopsy. The study was conducted between 1978 and 1985; indications for renal biopsy in decreasing hierarchical order were recently discovered uremia, nephrotic syndrome, chronic hematuria of less than two years duration with or without proteinuria or disturbed renal function, and chronic proteinuria of less than two years duration, of unknown origin. The main findings are fourfold. The incidence of IgA nephropathy and thin glomerular basal membrane lesions was high, 19 and 13 per 10(6) adults respectively, and the prevalence in patients biopsied because of non-azotemic chronic hematuria was 31% and 22%, respectively. In the normotensive non-azotemic adults biopsied because of chronic, mild proteinuria the prevalence of focal segmental glomerular sclerosis and vascular hyalinosis was both 41%. Of the patients biopsied because of nephrotic syndrome the prevalence of membranoproliferative glomerulonephritis (5%) was low, as was the incidence (less than 2 per 10(6) adults per year). Finally, the prevalence of diffuse sclerosing glomerulonephritis was 25% in patients biopsied because of uremia. This study is useful for the differential diagnosis of idiopathic glomerular disease.