Altered glomerular permselectivity and progressive sclerosis following extreme ablation of renal mass

Relation of glomerular injury to preglomerular resistance in experimental hypertension

A semiquantitative glomerular damage index (GDI) was determined for overall (O), superficial (S), and juxtamedullary (JM) glomeruli in four models of experimental hypertension in the rat to assess the severity and distribution of injury in light of present day knowledge of glomerular hemodynamics. After a four week period of similar hypertension, comparison of Group 1 (renal ablation) with Group 2 (aortic ligature) revealed OGDIs of 0.420 +/- 0.064 (SEM) vs. 0.062 +/- 0.019, P less than 0.0001, SGDIs of 0.250 +/- 0.071 vs. 0.035 +/- 0.007, P less than 0.0089, and JGDIs of 0.455 +/- 0.071 vs. 0.155 +/- 0.036, P less than 0.002. Within Group 1 the SGDI and JMGDI were not significantly different but within Group 2 the SGDI was less (P less than 0.005) than the JMGDI. Arterial/arteriolar damage was comparable in both groups. After an eight week period of similar hypertension, comparison of Group 3 (deoxycorticosterone-saline) with Group 4 (stroke-prone spontaneously hypertensive rats) showed OGDIs of 0.301 +/- 0.065 vs. 0.128 +/- 0.023, P less than 0.025, SGDIs of 0.289 +/- 0.096 vs. 0.072 +/- 0.015, P less than 0.044, and JMGDIs of 0.394 +/- 0.083 vs. 0.307 +/- 0.062, NS. Within Group 3 the SGDI and JMGDI were not significantly different, but within Group 4 the SGDI was less (P less than 0.002) than the JMGDI. Vascular damage in the two groups was comparable. Taking into account known physiologic data, the findings are consistent with the idea that increased preglomerular resistance is protective of glomeruli, whereas decreased resistance with increased pressure and/or flow is injurious.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathogenesis of diabetic microangiopathy. The hemodynamic view

Multiple factors, including altered levels of vasoactive substances, altered vasomotor responsiveness, chronic plasma volume expansion, and tissue hypoxia, contribute to a state of generalized microvascular vasodilatation in early insulin-dependent diabetes mellitus. This vasodilatation, with the consequent elevation in capillary pressures and flows, may be the initiating mechanism leading to both renal and extrarenal diabetic microangiopathy. Sustained hemodynamic actions on the microvasculature, besides directly injuring the capillary wall, promote increased permeability to macromolecules and increased capillary wall proliferation, with consequent thickening of basement membranes and luminal narrowing. These changes eventuate in complete microvascular obstruction and further vasodilatation of less damaged capillaries, thereby ensuring their eventual destruction. The ensuing complications depend on the nature of the surrounding tissue, ranging from reduction of functional reserve, as seen in skeletal muscle, to the devastating functional consequences observed in organs with endarterial circulation such as the kidney and retina.

Glomerular injury in uninephrectomized spontaneously hypertensive rats. A consequence of glomerular capillary hypertension

Micropuncture and/or morphologic studies were performed in intact Wistar-Kyoto rats (WKY) (group 0), intact spontaneously hypertensive rats (SHR) (groups 1 and 5), uninephrectomized (UNX) WKY (groups 2 and 6), and UNX SHR (groups 3 and 4, 7 and 8). UNX was performed when rats were 5 wk of age. Groups 0-4 were observed for 34 wk after which whole kidney clearance and morphologic studies were performed. Groups 5-8 underwent micropuncture study at 10 wk of age. Groups 4 and 8 were fed a diet containing 6% protein. All other rats ingested standard laboratory diet. 5 wk after UNX, normotensive group 6 had higher single nephron glomerular filtration rate (SNGFR) and initial glomerular plasma flow rate (QA) than intact, hypertensive group 5. Glomerular transcapillary hydraulic pressure difference (delta P) was similar in these two groups. Hypertensive group 7 exhibited less elevation in SNGFR and QA than group 6, but delta P was significantly increased. The presence of glomerular capillary hypertension in UNX SHR at 10 wk was associated with the development of significant proteinuria and an increased incidence of mesangial expansion and glomerular sclerosis at 7 mo (group 3) as compared with groups 0, 1, and 2. Protein restriction prevented the development of increased delta P in UNX SHR (group 8) and also conferred long-term protection from increased urinary protein excretion and glomerular injury (group 4). These studies suggest that glomerular capillary hypertension predisposes to glomerular injury in this model of hypertension with reduced renal mass.

Adriamycin-induced nephropathy as a model of chronic progressive glomerular disease

Serial changes in urine protein, blood chemistry, and histology of the kidney were investigated in rats for 28 weeks after injections of adriamycin (ADR). Massive proteinuria, hypoalbuminemia, and hyperlipidemia were observed at week 4 and throughout the experiment. Both BUN and serum creatinine began to increase at week 16 and reached the uremic level at week 28. Light microscopic study of the kidney demonstrated a normal appearance at week 4, vacuole formation in glomerular tuft at weeks 8 and 12, focal and segmental glomerular sclerosis at weeks 16 and 20, and extensive glomerular sclerosis with tubulointerstitial degenerations at weeks 24 and 28. Immunohistologically, IgM with a small amount of IgG and C3 appeared in the sclerosing glomeruli from week 16. Aggregated human IgG, injected intravenously at week 24, had accumulated mainly in the glomeruli. Electron microscopy revealed degenerative changes of glomerular epithelial cells with small vacuoles in the cytoplasm at week 4. Size of vacuoles increased at the later stage. In conclusion, ADR produced chronic, progressive glomerular changes in rats, which led to terminal renal failure. The segmental glomerular sclerosis and IgM-dominant glomerular deposition in these animals are similar to pathological characteristics of focal and segmental glomerular sclerosis seen clinically.

Eicosanoids in experimental and human renal disease

The renal prostaglandins and thromboxanes are powerful autacoids with potential effects on renal hemodynamics, salt and water metabolism, and the immune system. The possibility of adverse effects on renal function in certain patients with renal disease due to cyclooxygenase inhibition with nonsteroidal anti-inflammatory drugs has long been appreciated. Experimental evidence indicates that renal prostaglandin and thromboxane production is increased in several models of renal disease and that similar decrements in renal function occur with cyclooxygenase inhibition and may be due to inhibition of vasodilator prostaglandins. Additionally, several investigators have shown that administration of prostaglandins may be therapeutic in some forms of renal disease, particularly immunologically mediated diseases. Dietary modification to affect prostaglandin production has also been promising in certain experimental models. In contrast to vasodilator prostaglandins, thromboxane is a potent vasoconstrictor and would be expected to have adverse effects on renal function. Despite demonstration of elevated glomerular thromboxane, studies using inhibitors of thromboxane synthesis in immunologically mediated glomerular disease have been disappointing. There is some evidence, however, that these drugs may be of benefit in ureteric obstruction and renal transplant rejection.

Progressive glomerular sclerosis in experimental antiglomerular basement membrane glomerulonephritis

A model of chronic progressive glomerular sclerosis in experimental antiglomerular basement membrane (anti-GBM) glomerulonephritis was developed in Wistar rats. Wistar rats given the accelerated form of anti-GBM anti-body glomerulonephritis initially developed significant proteinuria and renal insufficiency associated primarily with a decrease in glomerular filtration rate (GFR) with normal renal clearance of para-aminohippuric acid and with markedly reduced filtration fraction. The glomerular functional abnormalities were associated with marked glomerular hypercellularity due to leukocytic infiltration as well as proliferation of intrinsic glomerular cells with crescent formation. Late in the course of the disease, by day 21, GFR had fallen further, associated with a parallel decrease in the clearance of para-aminohippuric acid and a normal filtration fraction. At this stage, glomerular hypercellularity had diminished and was replaced by glomerular sclerosis. The model appears to be a reproducible form of chronic glomerulosclerosis and demonstrates that the chronic phase of glomerular basement membrane (GBM) glomerulonephritis is distinctly different from that of the acute phase. It provides a controllable setting to study the glomerular sclerotic process independent of the initial inflammatory changes.

Adriamycin-induced glomerulosclerosis in the rat

To evaluate long-term effect of sustained proteinuria induced by a single injection of adriamycin (ADR) on occurrence of focal segmental glomerulosclerosis (FSG), we treated 50 Sprague-Dawley (SD) rats, weighing 250 g with 5 mg/kg body weight of ADR. After six months of heavy proteinuria, 40% of ADR-treated rats did not develop FSG. In the remaining 60% of animals, a mild FSG was observed associated with the presence of large tubular casts and interstitial inflammation. Glomerulosclerosis was never observed in absence of tubulointerstitial lesions. Nine months after ADR, all rats exhibited FSG with renal insufficiency but the severest changes were restricted to the tubulointerstitial level. Our results indicate that chronic proteinuria induced by ADR is a relatively good model of glomerular sclerosis, however, the cause of glomerular sclerosis is probably different from that operating in other experimental models of FSG. Both sclerotic changes and progression of disease seem to be dependent on formation of tubular casts with consequent interstitial changes. This study raises the question of the relative role of tubulointerstitial changes in the subsequent development of FSG.

The progression of adriamycin-induced nephrotic syndrome in rats and the effect of captopril

The progression of adriamycin-induced nephrotic syndrome in rats was studied over a 3-month period. The effect of an angiotensin-converting enzyme inhibitor, captopril, on this model of renal disease, was also studied. Two weeks following a single iv injection of adriamycin, rats were divided into two treatment groups: one received a daily po dose of captopril and the other received a placebo. Measurements of renal function were performed at 4, 8, and 11 weeks following the initiation of therapy. Necropsies and light microscopic evaluation of the kidneys were performed at the end of the treatment period. Functional and morphologic alterations in both groups of rats were compared to each other and to normal age/weight-matched control rats studied over the same time period. At 13 weeks following the administration of adriamycin, both treatment groups had significant renal dysfunction when compared to normal controls. In addition to severe proteinuria, rats receiving adriamycin exhibited polyuria, polydipsia, increased plasma urea nitrogen and plasma creatinine, and decreased endogenous creatinine clearance. They had severe generalized kidney lesions characterized by tubular dilation and atrophy, cast formation, interstitial fibrosis and lymphocytic infiltration, and focal, global glomerulosclerosis. The histopathologic ranking of the kidneys was correlated with some antemortem laboratory parameters but not with the degree of proteinuria. Captopril had no ameliorating effects on the progression of renal disease. Certain findings indicate that captopril may actually have promoted the deterioration of renal function. We conclude that adriamycin-induced nephrotic syndrome in the rat is a progressive disease resulting in generalized renal dysfunction, and that captopril, at the dose given in this experiment, is unable to slow the progression of the disease.

Captopril slows the progression of chronic renal disease in partially nephrectomized rats

The effect of captopril, an angiotensin-converting enzyme inhibitor, on the progression of chronic renal disease was studied in rats subjected to partial nephrectomy. Following ablation of approximately 70% of their renal mass, rats were divided into three treatment groups: group I received a placebo treatment; group II received daily po administrations of captopril; group III received captopril at the same dosage schedule as group II, but the drug was not given for 4 weeks in the middle of the treatment period. Measurements of renal function were performed at 4-week intervals, and light microscopic evaluation of the remnant kidneys was performed following 19 weeks of treatment. Deterioration of renal function, as measured by endogenous creatinine clearance, plasma creatinine, and plasma urea nitrogen, progressed more rapidly in group I than the other two groups. Twenty-four-hour urinary protein excretion was higher in group I than the others, except in group III following the 4-week period when captopril was not administered. Morphologic damage in the remnant kidney was significantly greater in group I than group II (p = 0.007). The renal lesions in the rats of group III were intermediate in severity. Histopathologic ranking of the remnant kidneys was correlated with antemortem laboratory parameters (r greater than or equal to 0.50; p less than 0.05). In a second experiment, similarly nephrectomized rats receiving po captopril daily had significantly longer survival, at 260 days, postnephrectomy than rats receiving a placebo (p = 0.0045). We conclude that captopril retards the progression of renal damage and increases survival time in this model of chronic renal disease. The mechanism may involve the alteration of potentially harmful intraglomerular hemodynamic changes which occur in the remnant kidney model.

Glomerular mesangium: its function and relationship to angiotensin II

The glomerular mesangium is composed of mesangial cells and an intercellular material, the mesangial matrix. Partly because of its unique anatomic location, the mesangium appears to be susceptible to immune- and non-immune-mediated injury. Mesangial cells have characteristics similar to smooth muscle cells, and their surface is covered with receptors that bind a variety of vasoactive substances. The glomerular mesangium seems to play an important role in the physiologic regulation of the glomerular microcirculation. There is evidence that a plasmic flow carrying macromolecules circulates through the mesangium. Changes in glomerular hemodynamic determinants and in the release and/or production of vasoactive substances, particularly angiotensin II, can greatly influence the mesangial movement of macromolecules. Quantitative and/or qualitative alterations in the mesangial movement of macromolecules may lead to mesangial injury.

Therapeutic implications of hypertension-induced glomerular injury. Comparison of enalapril and a combination of hydralazine, reserpine, and hydrochlorothiazide in an experimental model

Systemic hypertension does not always reflect concomitant glomerular hypertension. At similar levels of systemic hypertension, glomerular injury occurs only in kidneys that lack protective preglomerular vasoconstriction, which results in glomerular hypertension. indeed, glomerular hypertension and glomerular injury do not develop in rats with spontaneous hypertension that have effective preglomerular vasoconstriction. In the experiments reported herein, the normal adaptive response (afferent arteriolar dilation) to a reduction of one and five-sixths of the renal mass in rats with spontaneous hypertension was examined to ascertain whether that response would expose the remaining nephrons to the injurious effects of high perfusion pressure. In addition, the efficacies of two different antihypertensive regimens were compared. Rats with spontaneous hypertension received either no therapy, or a combination of hydralazine, reserpine, and hydrochlorothiazide, or the angiotensin converting enzyme inhibitor enalapril. Three weeks after ablation of one and five-sixths of the renal mass, blood pressure, glomerular filtration rate, urinary protein excretion, and histologic injury scores for mesangial expansion and glomerulosclerosis were determined. Untreated rats with hypertension had severe glomerulosclerosis and mesangial expansion. Both antihypertensive regimens normalized systemic blood pressure and reduced glomerulosclerosis. However, enalapril was more effective than the combination of hydralazine, reserpine, and hydrochlorothiazide in reducing the exaggerated glomerular filtration rate (0.52 +/- 0.40 versus 0.82 +/- 0.10 ml per minute; p less than 0.05), the injury score for mesangial expansion (79 versus 103; p less than 0.05), and the degree of proteinuria (32 +/- 4 versus 42 +/- 3 mg per 24 hours; p less than 0.05). Persistence of hyperfiltration accompanied by increased mesangial expansion, may lead to progression of glomerular damage despite "adequate" control of systemic hypertension, as observed in rats treated with a combination of hydralazine, reserpine, and hydrochlorothiazide.

Treatment of severe nephrotic syndrome with meclofenamate: an uncontrolled pilot study

The effect of meclofenamate on urinary protein excretion, level of serum albumin, and renal function was studied prospectively in 30 patients with corticosteroid-resistant severe nephrotic syndrome: 16 with focal segmental glomerulosclerosis, 12 with membranous glomerulopathy, and 2 with minimal-lesion nephropathy. Seventeen patients had a 40% or more reduction in urinary protein excretion ("responders"), and the decrease continued during long-term treatment. Meclofenamate therapy was discontinued after 2 months in eight "nonresponders" and in five other patients because of side effects (progressive increase in the level of serum creatinine in two, diarrhea in two, and pruritus in one). In responders, we recorded the following findings (mean +/- SD): urinary protein excretion decreased from 13.0 +/- 5.2 g/24 h to 7.2 +/- 3.5 g/24 h in 2 to 4 weeks and continued to decrease to 4.1 +/- 1.4 g/24 h at the time of the last follow-up study (median duration, 12 months; range, 6 to 36 months; P less than 0.01, 2 to 4 weeks versus later follow-up); the level of serum albumin increased from 1.9 +/- 0.5 g/dl to 2.9 +/- 0.7 g/dl (P less than 0.001) in 2 to 4 weeks; the level of serum cholesterol decreased from 413 +/- 125 mg/dl to 346 +/- 114 mg/dl (P less than 0.005) at the time of the last follow-up examination; and renal function remained unchanged from the baseline study to the follow-up study (serum creatinine 1.5 +/- 0.5 mg/dl versus 1.6 +/- 0.4 mg/dl and glomerular filtration rate 60.5 +/- 29.2 ml/min per 1.7 m2 versus 64.1 +/- 25.5 ml/min per 1.7 m2).(ABSTRACT TRUNCATED AT 250 WORDS)

Predominance of hemodynamic rather than metabolic factors in the pathogenesis of diabetic glomerulopathy

Six groups of Munich-Wistar rats underwent micropuncture study 2-10 weeks and morphologic studies 11-13 months after induction of streptozotocin diabetes or after sham treatment. Diabetic rats received diets containing 6% (group D6), 12% (D12), or 50% protein (D50) and were maintained under similar conditions of moderate hyperglycemia by daily injections of ultralente insulin. Age- and weight-matched normal control rats were also given 6% (Group N6), 12% (N12), or 50% protein (N50). Kidney weight, whole-kidney and single-nephron glomerular filtration rate, glomerular plasma flow, and mean glomerular transcapillary hydraulic pressure difference were higher in D50 rats than in all other groups and predisposed this group to marked and progressive albuminuria. Likewise, histological examination of the kidneys disclosed areas of sclerosis in 19.6% of glomeruli in D50 rats; the frequency of such lesions was less than 2.5% in all other groups. These findings indicate that the metabolic disorder seen in stable, moderately hyperglycemic diabetic rats does not lead to glomerulopathy as long as elevations in glomerular pressures and flows are prevented.

Pathophysiology of chronic tubulo-interstitial disease in rats. Interactions of dietary acid load, ammonia, and complement component C3

The human end-stage kidney and its experimental analogue, the remnant kidney in the rat, exhibit widespread tubulo-interstitial disease. We investigated whether the pathogenesis of such tubulo-interstitial injury is dependent upon adaptive changes in tubular function and, in particular, in ammonia production when renal mass is reduced. Dietary acid load was reduced in 1 3/4-nephrectomized rats by dietary supplementation with sodium bicarbonate (NaHCO3), while control rats, paired for serum creatinine after 1 3/4 nephrectomy, were supplemented with equimolar sodium chloride. After 4-6 wk, NaHCO3-supplemented rats demonstrated less impairment of tubular function as measured by urinary excretory rates for total protein and low molecular weight protein and higher transport maximum for para-aminohippurate per unit glomerular filtration rate, less histologic evidence of tubulo-interstitial damage, less deposition of complement components C3 and C5b-9, and a lower renal vein total ammonia concentration. Such differences in tubular function could not be accounted for simply on the basis of systemic alkalinization, and differences in tubular injury could not be ascribed to differences in glomerular function. Because nitrogen nucleophiles such as ammonia react with C3 to form a convertase for the alternative complement pathway, and because increased tissue levels of ammonia are associated with increased tubulo-interstitial injury, we propose that augmented intrarenal levels of ammonia are injurious because of activation of the alternative complement pathway. Chemotactic and cytolytic complement components are thereby generated, leading to tubulo-interstitial inflammation. Thus, alkali supplementation reduces chronic tubulo-interstitial disease in the remnant kidney of the rat, and we propose that this results, at least in part, from reduction in cortical ammonia and its interaction with the alternative complement pathway.

Renal hemodynamics and glomerular morphology in repetitively pregnant aging rats

Measurements were made of renal and glomerular hemodynamics and glomerular morphology in repetitively pregnant and age-matched virgin female Munich-Wistar rats. Repetitive pregnancies and lactation provide a stimulus to chronic increases in glomerular filtration rate (GFR) and these rats were studied, by micropuncture, approximately 4 to 6 weeks after the end of the fifth gestation/lactation cycle. No differences were seen in GFR or renal plasma flow (RPF) rate nor in any of the determinants of single nephron filtration rate (SNGFR) in repetitively pregnant compared to virgin rats, although SNGFR itself was slightly but significantly elevated in repetitively pregnant rats. There was no evidence of systemic hypertension, proteinuria, or abnormal glomerular morphology in either group despite their advanced age (approximately 42 to 46 weeks). Thus, the moderate chronic increase in GFR due to the stimulus of repetitive pregnancy and lactation does not lead to eventual deterioration in renal function or structural abnormalities.

Low-protein diet prevents glomerular damage in adriamycin-treated rats

Adriamycin (ADR) induces glomerular damage in rats with persistent proteinuria which develops 13 to 15 days after a single intravenous (i.v.) injection (5 mg/kg). Electron microscopy (EM) shows alterations of glomerular visceral epithelial cells with foot process fusions. The disease resembles minimal change nephropathy in humans. We studied the effect of two isocaloric diets with different protein content on urinary protein excretion, renal function, and glomerular morphology in rats treated with ADR. Six groups of rats were used. Group 1 received a single i.v. injection of ADR and was fed a standard diet containing 20% protein. Group 2 was fed a low-protein diet containing 6% protein starting 7 days before ADR. Group 3 was fed a low-protein diet starting the day after ADR. Group 4 served as control. Two additional groups of rats (5 and 6) were used to study the kidney distribution of ADR. Unlike animals fed the standard diet, animals fed the low-protein diet did not develop proteinuria. The kidney distribution of ADR measured at different intervals after drug injection was not influenced by the diet. Renal function as determined by glomerular filtration rate (GFR) and renal plasma flow (RPF) was not significantly modified in nephrotic rats receiving the standard diet compared to control animals. The low-protein regimen induced a significant elevation in RPF compared to the standard diet, but had no influence on GFR. Light and transmission EM studies showed alterations of glomerular visceral epithelial cells with fusion of foot processes in rats fed the standard diet, whereas no significant abnormalities of glomerular epithelial cells were detectable in animals receiving the low-protein diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of protein intake on renal function and structure in partially nephrectomized rats

To examine the effect of high protein intake on renal function and structure in rats with 5/6 nephrectomy chronic renal failure, we pairfed rats with chronic renal failure and sham-operated control rats diets of 14 or 37% protein content for up to 6 months. High protein intake accelerated mortality in rats with chronic renal failure and resulted in a more rapid rate of decrease in renal function as established by plotting the reciprocal of plasma creatinine versus time. High protein intake also increased urine protein excretion in experimental and control rats. High protein intake was associated with increased tubular dilatation and interstitial inflammation, both of which were striking features in rats with chronic renal failure. Glomerular sclerosis was prominent in rats with chronic renal failure. These rats had smaller glomerular tuft dimensions than control rats irrespective of their protein intake. We conclude that high protein intake accelerates the course of chronic renal failure in rats. The pathologic process involves glomerular sclerosis; however, interstitial inflammation and renal tubular changes leading to cyst formation also appear to influence the process adversely.

Role of hypertension in progressive glomerular immune injury

The relationship between hypertension, ferritin-antiferritin mesangial immune injury (FIC), and progressive glomerular damage was studied in hypertensive (8% NaCl chow) Dahl salt-sensitive rats (DS) and in spontaneously hypertensive rats (SHR). The glomeruli of SHR are protected from the increased perfusion pressure that accompanies systemic hypertension by preglomerular vasoconstriction, while the glomeruli of hypertensive DS are not. Blood pressure, serum creatinine levels, urinary protein excretion, and glomerular injury (assessed by semiquantitative morphometric analysis) were determined in 20-week-old SHR and DS with FIC. In addition, half of a group of 20-week-old SHR with FIC were uninephrectomized and progression of glomerular injury was assessed 12 weeks later. Control rats for each of the groups did not receive FIC. Our studies showed that more extensive mesangial expansion and glomerulosclerosis developed in hypertensive DS with FIC than in rats without FIC. Glomerular injury in DS with FIC affected cortical and deep glomeruli. Similarly, hypertensive SHR with FIC had minimal damage in cortical glomeruli. In deep glomeruli of SHR, mesangial expansion was similar to that of DS, but glomerulosclerosis was absent. In SHR, a 50% reduction in renal mass, a maneuver known to decrease preglomerular vasoconstriction, resulted in mesangial expansion similar to that in DS in cortical glomeruli while deep glomeruli developed mesangial expansion as well as glomerulosclerosis. Our results suggest that when hypertension and mesangial immune injury coexist with renal vasodilatation (as occurs in DS with 2 kidneys and in SHR after uninephrectomy), they act synergistically to induce progressive glomerular damage. Similar mechanisms may be operative in hypertensive humans with glomerulonephritis and may condition the rate of progression to renal insufficiency.

Effects of mesangial localization of polyvinyl alcohols on glomerular basement membrane thickness

We studied the effects of mesangial localization of polyvinyl alcohols (PVA) on glomerular basement membrane (GBM) thickness in inbred Lewis rats. To avoid possible influences of PVA redistribution after localization in liver, lung, and other organs, the kidneys of rats given PVA were transplanted into uninephrectomized normal rats. Normal kidneys transplanted into normal rats served as a control. GBM thickness at the time of transplantation was the same in PVA kidneys as in normal kidneys. However, by 18 weeks post-transplant GBM thickness was greater in PVA kidneys, and this increase was sustained at 30 weeks. Within the glomeruli of PVA kidneys, lobules with marked mesangial PVA accumulation had more marked GBM thickening than lobules with little or no PVA accumulation. It is concluded that changes within the mesangium can influence GBM thickness. Whether this represents a direct effect of mesangial architectural distortion, a consequence of local phlogistic activities such as the influx of macrophages into the mesangium of glomeruli with PVA localization, or the result of intraglomerular hemodynamic perturbations is unclear.

Focal sclerosis of hypertrophied glomeruli in solitary functioning kidneys of humans

Morphometric data on glomerular size are presented on three patients with solitary functioning kidneys and one with bilateral oligomeganephronic hypoplasia. Renal biopsy of each of two patients with a congenitally absent kidney (unilateral renal agenesis) and a patient with oligomeganephronie, all with proteinuria and renal insufficiency, reveal increases of mean glomerular diameters of at least 1.75X and mean glomerular volumes greater than 5X. These dimensions, which are in the range of maximal increases recorded for man, are associated in all three biopsies with focal sclerosis of the hypertrophied glomeruli. By contrast, the functionally fully-compensated solitary kidney of a patient who lost function of the contralateral kidney from acquired disease, is characterized by the absence of focal glomerulosclerosis and by glomerular enlargement of significantly lesser degree (increased mean diameter 1.24X and mean volume less than 2X). These observations correlate glomerular injury with glomerular size and suggest that in the setting of reduced nephron numbers, nephron destruction via focal glomerulosclerosis may be initiated when compensatory glomerular hypertrophy has reached its limits.

Urinary albumin excretion after donor nephrectomy

Surgical ablation of renal tissue in animals leads to compensatory hyperfiltration, hypertension, and focal glomerular sclerosis in remnant nephrons, in association with albuminuria; the detection of slightly elevated urinary albumin (microalbuminuria) has been shown to predict later, more severe renal disease in diabetics. To determine whether unilateral nephrectomy in humans initiates a similar pathogenetic sequence, we measured urinary albumin excretion (UalbV), total protein excretion (UprotV), creatinine clearance (Ccreat) and blood pressure in 22 transplant donors before and at intervals up to 3 years after donor nephrectomy. Urinary albumin was determined using a sensitive enzyme immunoassay (ELISA). Mean Ccreat fell on average to 68% of prenephrectomy values at all times after nephrectomy, indicating a rise of 33% in average single nephron filtration rate. Mean absolute and fractional albumin excretion rates and UprotV values were transiently elevated one week postnephrectomy, but returned thereafter to values not significantly different from prenephrectomy values. Blood pressure rose slightly, but significantly, with time after nephrectomy. Average increases of 10 mm and 5 mm in systolic and diastolic pressures, respectively, were noted by 2 years after surgery. In this study, there was no evidence of glomerular injury from hyperfiltration in the 3 years following donor nephrectomy.

Mesangial function and glomerular sclerosis in rats with aminonucleoside nephrosis

The possible relationship between mesangial dysfunction and development of glomerular sclerosis was studied in the puromycin aminonucleoside (PAN) model. Five male Wistar rats received repeated subcutaneous PAN injections; five controls received saline only. After 4 weeks the PAN rats were severely proteinuric (190 +/- 80 mg/24 hr), and all rats were given colloidal carbon (CC) intravenously. At 5 months glomerular sclerosis was found in 7.6 +/- 3.4% of the glomeruli of PAN rats; glomeruli of the controls were normal. Glomeruli of PAN rats contained significantly more CC than glomeruli of controls. Glomeruli with sclerosis contained significantly more CC than non-sclerotic glomeruli in the same kidneys. CC was preferentially localized within the sclerotic areas of the affected glomeruli. Since mesangial CC clearance from the mesangium did not change during chronic PAN treatment, we conclude that this preferential CC localization within the lesions is caused by an increased CC uptake shortly after injection in apparent vulnerable areas where sclerosis will develop subsequently. Cluster analysis showed a random distribution of lesions in the PAN glomeruli in concordance with the random localization of mesangial areas with dysfunction in this model. Similar to the remnant kidney model in PAN nephrosis the development of glomerular sclerosis may be related to "mesangial overloading."

Inhibition of thromboxane synthesis ameliorates the progressive kidney disease of rats with subtotal renal ablation

Ablation of greater than 70% of renal mass in the rat results in hypertension, proteinuria, and glomerular sclerosis of the remnant kidney. Rats with a remnant kidney have increased excretion of thromboxane in the urine when compared with normal rats. Chronic oral administration of OKY 1581, an inhibitor of thromboxane synthesis, in rats with a remnant kidney increases renal blood flow and glomerular filtration rate (GFR), decreases protein and thromboxane excretion in the urine, lowers blood pressure and cardiac index, and improves renal histology. The degree of hypertrophy of the remnant kidney was unaffected by administration of OKY 1581. Calculated values for single nephron plasma flow and GFR were significantly greater in rats with remnant kidneys given OKY 1581 than in rats given saline. Acute i.v. administration of OKY 1581 increased renal plasma flow and GFR in rats with a remnant kidney but not in normal rats or rats with a remnant kidney previously treated with acetylsalicyclic acid. OKY 1581 markedly inhibited platelet aggregation. We suggest that in this model of renal disease platelet aggregation and intraglomerular thrombosis play a key role in the development of glomerulosclerosis. Inhibition of platelet aggregation prevents development of glomerulosclerosis, hypertension, and cardiac hypertrophy. We suggest that hyperperfusion and hyperfiltration per se occurring in remnant glomeruli are not directly responsible for the development of glomerulosclerosis.

Regional variations in British alcohol morbidity rates: a myth uncovered? I: Clinical surveys

Officially recorded rates of many alcohol related problems are much higher in the north than in the south of Britain. To try to shed some light on this the pattern and threshold for use of psychiatric and medical hospital services for alcohol dependence, abuse, and psychosis were studied in three areas differing greatly in official rates of alcohol related problems--namely, the Highland and Tayside regions in Scotland and part of the South East Thames region in England. The disparity in psychiatric admissions for alcohol dependence, abuse, and psychosis were found to be largely explained by admission policies which reflected geographical factors. The results of this study did not support the conventional view that rates of treated morbidity due to alcohol are appreciably higher in the north.

Selective effect of low protein diets in chronic renal diseases

It has recently been established that the rate of progression of chronic renal failure in man can be slowed by restricting dietary protein. Consequently, the short term and long term effects of a low protein diet on the course of different chronic nephropathies were studied in an attempt to delineate the factors that determine the response to such a diet. When a low protein diet was given for six months renal function improved significantly in nine patients with chronic tubulointerstitial nephritis (p less than 0.025); the diet had a marginally beneficial effect in 12 patients with chronic glomerulonephritis (p less than 0.05) and no effect in nine with hypertensive nephrosclerosis. The heterogeneous functional response in the patients with chronic glomerulonephritis correlated closely with the effect of the diet on these patients' proteinuria (r = 0.76, p less than 0.01). In a short term study (four weeks) of 12 patients with chronic renal failure changes in renal plasma flow were proportional to dietary protein intake. Renal vascular resistance fell during a high protein diet and increased when dietary protein was restricted. The changes in renal plasma flow during the low protein diet correlated well with the patients' long term functional response to the diet (r = 0.76, p less than 0.01). It is concluded that the response to a low protein diet in chronic renal failure is determined, firstly, by the nature of the underlying nephropathy, with maximal benefit being observed in non-glomerular disorders; secondly, by the effect of the diet on the proteinuria in chronic glomerulonephritis; and, thirdly, by the haemodynamic response to the diet, with patients with a reactive renal vascular bed improving with a low protein diet.

Structural-functional relationships in diabetic nephropathy

Renal biopsies in 45 patients with insulin-dependent diabetes mellitus (IDDM) were examined by semiquantitative light microscopy and quantitative electron microscopic stereologic morphometry. In these 14 males and 31 females, aged 13-52 yr, who had had IDDM for 2.5-29 yr there was no strong relationship between either glomerular basement membrane (GBM) thickness or mesangial expansion and duration of IDDM. There was only a weak relationship between the thickness of the GBM and expansion of the mesangium. Thus, GBM thickening and mesangial expansion in IDDM occur at rates that often differ from one another and that vary greatly among patients. The clinical manifestations of diabetic nephropathy, albuminuria, hypertension, and decreased glomerular filtration rate related poorly or not at all to GBM thickening. In contrast, all light and electron microscopic measures of mesangial expansion were strongly related to the clinical manifestations of diabetic nephropathy, although in the absence of these clinical findings, it was not possible to predict the severity of any of the diabetic glomerular lesions. Mesangial expansion had strong inverse correlations with capillary filtering surface area density. It is hypothesized that mesangial expansion could lead to glomerular functional deterioration in IDDM by restricting the glomerular capillary vasculature and its filtering surface. However, capillary closure, glomerular sclerosis, and interstitial fibrosis could also contribute to the clinical manifestations of this disorder.

Cyclosporine-associated chronic nephropathy

We evaluated glomerular filtration in 17 recipients of heart transplants who were treated for 12 months or longer with cyclosporine (cyclosporin A). The control group consisted of 15 heart-transplant recipients who were treated with azathioprine and who had also survived for at least 12 months. Despite an equivalent cardiac output, the glomerular filtration rate was depressed (51 +/- 4 vs. 93 +/- 3 ml per minute, P less than 0.005) in transplant recipients treated with cyclosporine. Cyclosporine treatment was also associated with reduced renal plasma flow (320 +/- 21 vs. 480 +/- 30 ml per minute, P less than 0.001). A trend toward restricted transglomerular transport of neutral dextrans (radii, 2.4 to 5.8 nm) in cyclosporine-treated recipients suggested an intrinsic loss of ultrafiltration capacity by glomerular capillaries rather than a hemodynamic basis for the reduced glomerular filtration rate. Histopathologic examination of the kidneys of five cyclosporine-treated patients with glomerular hypofiltration revealed a variable degree of tubulointerstitial injury accompanied by focal glomerular sclerosis. Among the 32 heart-transplant recipients treated for more than 12 months with cyclosporine at our center, end-stage renal failure developed in 2. We conclude that long-term cyclosporine therapy may lead to irreversible and potentially progressive nephropathy. We recommend that cyclosporine be used with restraint and caution until ways are found to mitigate its nephrotoxicity.

Mesangial immune injury, hypertension, and progressive glomerular damage in Dahl rats

Hypertension frequently accompanies chronic glomerulonephritis. Mesangial injury and glomerulosclerosis are common in glomerulonephritis and are often harbingers of progressive glomerular destruction. Thus, in a model of mesangial immune injury we studied the relationship between hypertension, mesangial injury, and glomerulosclerosis. We induced mesangial ferritin-antiferritin immune complex disease (FIC) in Dahl salt-sensitive (S) and salt-resistant (R) rats. S and R rats with FIC were fed chow containing 0.3% NaCl until 14 weeks of age and then switched to 8.0% NaCl chow until 28 weeks of age. Groups of control S and R rats (no FIC) were either fed 0.3% NaCl for 28 weeks or switched to 8.0% NaCl chow at 14 weeks of age. Blood pressure, serum creatinine, urinary protein, and glomerular injury (assessed by semiquantitative morphometric analysis) were determined at 14 and 28 weeks of age. R rats with or without FIC did not develop hypertension; mesangial injury was minimal. At 14 weeks of age, only S FIC rats developed hypertension, proteinuria, significant mesangial expansion and early glomerulosclerosis. At 28 weeks of age, proteinuria, mesangial expansion, and glomerulosclerosis were significantly more severe in hypertensive S rats with FIC than in those without FIC. These studies show that despite a normal salt intake, mesangial injury hastened the onset of hypertension, but only in rats genetically predisposed to hypertension (S FIC at 14 weeks). High dietary salt further aggravated hypertension, which, in turn, magnified both mesangial injury and glomerulosclerosis. Clinically, the different rates of progression of human glomerulonephritis associated with hypertension may be in part dependent on similar mechanisms.

Hypertension and proteinuria: long-term sequelae of uninephrectomy in humans

Renal function and blood pressure were assessed in 52 renal allograft donors 10 years or more following uninephrectomy, and their current function compared to their pre-uninephrectomy function as well as to age- and sex-matched control subjects consisting of inpatient potential renal donors and a normal "outpatient" population. The results show no significant deterioration in renal function as determined by serum creatinine or creatinine clearance, as a function of years post-uninephrectomy or age at the time of donation. A higher incidence of proteinuria and hypertension was found in male donors as compared to their pre-uninephrectomy values and to age- and sex-matched, inpatient and outpatient control subjects. Female donors had increased proteinuria when compared to pre-uninephrectomy and to age-matched, inpatient potential donors. However, the extent of proteinuria and hypertension was not significantly different from outpatient age-matched females with two kidneys. In our population, uninephrectomy is associated with mild proteinuria and hypertension.

The hyperfiltering glomerulus

The observation has been made that after any of a variety of initial renal injuries, nephron units that have been spared undergo structural and functional compensations. The functional compensation of increased perfusion of residual nephrons may present deleterious, maladaptive stresses to those surviving nephrons and lead to their ultimate destruction. This hypothesis provides a final common pathway for the progression of many different renal diseases to renal failure and explains the tendency of renal insufficiency to progress rather than stabilize.

Role of heparin as a protective agent following reduction of renal mass

To determine the mechanism by which heparin affords protection from damage to the remnant kidney following reduction of renal mass, either whole heparin or a low molecular weight fraction of heparin was administered to Munich-Wistar rats which had had 90% ablation of renal mass. The low molecular weight fraction differed from the whole heparin in that it had greatly decreased anticoagulant activity as measured by the United States Pharmacopoeia (USP) assay, and increased antifactor Xa activity. The morphological alterations were examined and various physiological features were studied. The administration of whole heparin to rats with reduction of renal mass resulted in prolonged clotting time, reduced BP elevation, elimination of albuminuria, and lessening of renal damage. No such differences were observed in the rats receiving the fraction of heparin or the control group to which no therapy was given. The inability of the fraction of heparin to prolong clotting time suggested that it was unable to inactivate the serine proteases of the coagulation cascade. It is probable that the protective effect of whole heparin in this model is due to its ability to inhibit serine proteases such as kallikrein and components of the coagulation cascade resulting in a beneficial alteration in glomerular hemodynamics, lowering of systemic BP, and anticoagulation.

Focal glomerulosclerosis in patients with unilateral nephrectomy

To investigate whether proteinuria and focal glomerulosclerosis (FSG) might develop in humans as well as in experimental models following a reduction in renal mass, we performed a retrospective study of 24 patients previously nephrectomized for unilateral renal disease. None of the patients presented signs of systemic diseases. Alport syndrome, essential hypertension, reflux nephropathy, and other abnormalities on intravenous pyelography. At the time of the first observation seven patients had pathological proteinuria (group 1) while 17 presented a normal protein excretion (group 2). All patients in group 1 and only 4 of 17 in group 2 were male. No other significant differences were found between the two groups. The median age at nephrectomy of the proteinuric patients was 22.3 years, and proteinuria developed after a mean period of 12.2 years. A renal biopsy was performed in four patients and showed a constant pattern of FSG. After a mean follow-up period of 7.3 years from the onset, proteinuria remains unchanged and renal function is well preserved in all the patients. In conclusion our series suggests that also in humans proteinuria and FSG might appear in solitary kidneys due to nephrectomy. This glomerular damage may result from the association of glomerular overload with other unidentified factors.

Alteration of glomerular anionic sites by the development of subepithelial deposits in experimental glomerulonephritis in the rat

Using highly cationic polyethleneimine, alteration of glomerular anionic sites were evaluated ultrastructurally in two types of rat glomerulonephritis (GN); chronic serum sickness GN and heterologous (passive) or autologous (active) Heymann's GN. Daily i.v. injections of egg white lysozyme in physiologic saline into presensitized rats led to the formation of numerous mesangial and subepithelial deposits. In the non-proteinuric period in which immune deposits were localized predominantly in the mesangium, anionic sites of the laminae rarae and the epithelial cell coat were clearly observed. In the subsequent proteinuric period in which numerous subepithelial deposits were superimposed, a broad loss of anionic sites in the epithelial cell coat was seen. Splitting and focal loss of anionic sites on the lamina rara externa adjacent to the subepithelial deposits were commonly observed both in passive and active Heymann's GN and in lysozyme GN. These findings indicate that the subepithelial deposits are closely involved in the development of proteinuria by injuring the anionic sites, especially those on lamina rare externa of the glomerular basement membrane.