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Unilateral renal disease was produced in rats by left renal perfusion in situ with the aminonucleoside of puromycin or with nephrotoxic serum. The uptake of colloidal carbon by the glomerular mesangium was increased in kidneys perfused with aminonucleoside or nephrotoxic serum compared to contralateral kidneys. The quantities of carbon within the glomerular mesangium remained increased in aminonucleoside perfused kidneys 14 days later. These studies demonstrate that alterations in glomerular mesangial function in aminonucleoside nephrosis and nephrotoxic serum nephritis are related to renal factors rather than differences in host milieu and may be involved in the pathogenesis of the morphologic lesions seen in chronic proteinuria.

In heterologous immune complex glomerulonephritis glomerular deposition of immune complexes occurs immediately after an injection with heterologous antibody directed against antigen, derived from the brush border of the tubules. The injected antibody is thought to combine with circulating Fx1A antigen to form immune complexes which subsequently are deposited in the glomeruli. However, perfusion of rat kidneys in absence of this antigen likewise resulted in prompt localization of immune complexes along the glomerular basement membrane. Further, Fx1A antigen was shown to be present in the capillary wall, especially in the filtration slits and on the cell membrane of epithelial cells. From these findings it was concluded that in this model of glomerulonephritis the deposited immune complexes are formed locally instead of being deposited from the circulation. This concept of "fixed antigen" may also be relevant to the pathogenesis of other forms of experimental glomerulonephritis and probably also for human glomerulonephritis.

The effects of prostacyclin infusion on endotoxin-induced generalized Shwartzman reaction were studied in pregnant rats. Four hours after administration of Escherichia coli endotoxin (0.4 mg) to pregnant rats on the 20th day of gestation, fibrin and platelet thrombi were observed in 72% of the animals. These findings were associated with a decrease in renal blood flow and glomerular filtration rate from 7.0 to 0.7 and 0.8 +/- 0.1 to 2.6 +/- 0.4 and 0.2 +/- 0.8 ml/minute, respectively (p less than 0.0001 and less than 0.05) and a decrease in platelet count (p less than 0.05). The infusion of prostacyclin, at a mean dose of 57 ng/kg/minute prior to and after administration of endotoxin strikingly inhibited the development of fibrin and platelet thrombi in glomerular capillaries (p less than 0.001). Despite hemodynamic changes which were similar to those in control animals, renal blood flow and glomerular filtration rate decreased from 7.2 +/- 0.2 and 0.9 to 2.9 +/- 0.03 and 0.3 +/- 0.1 ml/minute, respectively (p less than 0.001 and less than 0.025). In addition, the mean blood pressure decreased from 118 +/- 3.8 to 86 +/- 3.7 mm Hg (p less than 0.025), whereas the platelet count remained normal. We conclude that prostacyclin infusion prior to endotoxin administration significantly inhibits endotoxin-induced generalized Shwartzman reaction in pregnant rats.

Interstitial deposits of periodic acid-Schiff positive fibrillar material have been detected in a variety of diseases associated with tubulointerstitial pathology. This material has been shown to be Tamm-Horsfall protein by immunofluorescent, immunochemical, and electron microscopic studies. Prospective evaluation of 133 kidneys revealed deposits in 11 per cent. These deposits included medullary cystic disease (50 per cent), obstructive uropathy and vesicoureteral reflux (21 per cent), and tubulointerstitial disease (29 per cent). Tamm-Horsfall protein was also detected in Bowman's space in four cases of obstructive uropathy. It is proposed that these deposits result from severe tubular damage with release of Tamm-Horsfall protein from its normal intracellular and intralumenal locations into the renal interstitium. We speculate that the intersitial deposition of this sequestered protein may result in a continued inflammatory response and progressive renal damage.

Cells from human glomeruli explanted in tissue culture were grown and subcultivated up to 12 to 13 times. Light and electron microscopic studies revealed these cells to be morphologically distinct from fibroblasts. By electron microscopy, an extracellular material resembling basal lamina was seen and prominent intracellular microfilaments were evident. Immunofluorescent microscopy demonstrated reactivity of heterologous antiglomerular basement membrane antibody with aggregates of extracellular material. Absorption experiments using antiglomerular basement membrane antibody showed that the extracellular materiial shared some antigenic components with glomerular basement membrane. Antibody to cultured glomerular cells stained the mesangium and glomerular basement membrane of normal human kidney. This antibody was nephrotoxic in monkeys, induced proteinuria with proliferative glomerulonephritis, and localized to the mesangium and glomerular basement membrane of monkey glomeruli. These findings and the presence of prominent intracellular microfilaments (contractile elements) suggest that the glomerular cells may be of mesangial origin.

Intact and uninephrectomized genetically diabetic (db/db) mice (C57BL/KsJ) and their nondiabetic littermates (dm/m) had renal biopsies performed at 6 months of age. Renal tissues were studied by regular light microscopy and by a variety of immunohistochemical techniques. Intact db/db mice had peripheral mesangial thickening as compared to db/m mice. This thickening, predominantly due to increased mesangial matrix material, extended to the glomerular hilum and the extraglomerular mesangium of the juxtaglomerular apparatus. This abnormality was markedly increased an uninephrectomized db/db mice (db/db-UN) compared to intact db/db mice. Db/m-UN animals had slightly greater mesangial thickness than intact db/mice but less than that of db/db mice. Intact db/db mice had increased mesangial IgM staining compared to db/m mice and these differences were magnified by uninephrectomy. The IgM staining, especially in the diabetic mice, involved the peripheral mesangium and the glomerular hilum extending into extraglomerular mesangium and the distal tubule at the level of the macula densa. The tubular staining in the region of the juxtaglomerular apparatus was between the tubular basement membrane and the epithelial cells and between epithelial cells. The distal tubular epithelial cell cytoplasm also showed increased staining for IgM as the tubule coursed away from the glomerulus. These studies amplify the argument that alterations in glomerular hemodynamics influence the rate of development of diabetic glomerular lesions. Further, these diabetic mice appear to represent an important model for the study of mesangial macromolecular processing mechanisms.

The possibility that experimental diabetes could prepare for the generalized Shwartzman reaction was investigated in female Sprague-Dawley streptozotocin-induced diabetic rats. After 48 hours, 1 week, and 9 weeks of diabetes, the rats were injected with 2 mg/kg of endotoxin, and the animals were sacrificed 2, 4, 8, and 24 hours after endotoxin. Ninety percent of the diabetic animals given endotoxin developed massive glomerular capillary fibrin deposition accompanied by marked decrease in platelet count. The age- and sex-matched nondiabetic control rats had no such changes. This marked susceptibility to endotoxin, previously only reported in pregnant rats, was present as early as 1 week of diabetes. The degree of glycemic control greatly influenced the susceptibility of diabetic rats to the generalized Shwartzman reaction. Only 28% of the diabetic animals given insulin once daily (4.6 +/- 0.3 units, mean +/- SEM) and maintaining a blood glucose level of 269 +/- 19 mg/dl developed glomerular thrombi. In contrast, the diabetic animals that did not receive insulin and had a blood glucose level of 617 +/- 21 mg/dl all developed fibrin thrombi. We conclude that the diabetic state in rats induces a unique susceptibility to the generalized Shwartzman reaction following a single injection of endotoxin, which varies with the severity of the diabetic state. Although the pathogenesis is unclear, this phenomenon may reflect abnormalities in the glomerular capillary wall and/or the coagulation system that may be important in the development of microvascular complications. Furthermore, this phenomenon may, in the animal model, mirror the increased risk of the diabetic patient to intravascular coagulation with bacterial sepsis.

The uptake and disposal of injected aggregated human albumin (AHA) by the glomerular mesangium of normal mice was evaluated by immunoelectron microscopy. The injected AHA rapidly entered the mesangial matrix channels via endothelial fenestra at the axial pole of the lobules and reached maximal concentrations at 8 hours after injection. Small quantities of AHA were endocytosed by mesangial cells. Significant filtration of the polydispersed AHA, which included molecular albumin, was observed across both the peripheral glomerular basement membrane and the mesangial glomerular basement membrane. The injected AHA was observed in the juxtaglomerular region, between lacis cells, and in the wall of arterioles at early time periods after injection. A heavy fraction of AHA (molecular weight, greater than 1 million) was also readily taken up by the region and was found in the interstitial space in the vicinity of glomeruli at 2 1/2 hours after injection. This study demonstrates a method for sequential study of the distribution in the kidney of protein macromolecules of great biologic significance. The study confirms the existence of an efferent limb of mesangial drainage to the region of the juxtaglomerular region and the renal interstitium. The fact that very large aggregates readily transited this pathway and were found in the interstitial space offers additional support for the hypothesis that the renal lymphatics may participate in the clearance of macromolecules from the glomerular mesangium.

Tamm-Horsfall urinary glycoprotein (TH) is the primary constituent of urinary casts. The intracellular distribution of TH in normal rat kidney was determined by immunoelectron microscopy using horseradish peroxidase-labeled antibodies and compared with morphologic localization of TH by immunofluorescence and light immunoperoxidase microscopy. Electron microscopy revealed an intracellular localization of TH restricted to the thick ascending limb of the loop of Henle (ALH). In this nephron segment, TH was distributed on and between adjacent intercellular membranes and infolding intracellular membranes at the base of these cells, within Golgi vacuoles, apical vesicles, and on the luminal membranes. Macula densa cells were negative, although typical ALH cells across the lumen of the same tubular segment were positive. Other renal segments were negative for intracellular TH. The unique distribution of TH is consistent with the known function of the ALH as the diluting segment of the nephron. We speculate that the aggregation and gel formation of TH on and between ALH surface membranes may restrict water movement across the ALH. This influence on permeability would be an important role for TH in the generation of concentration gradients for the countercurrent multiplier system of the kidney.

Immunopathologic analysis was carried out on renal tissue from patients with membranoproliferative glomerulonephritis, nine with type I and nine with type II (dense deposit disease). A specific finding in all patients with type II, but not type I, was the presence of C3 along the margin but not within the central portion of dense deposit material in the glomerular basement membrane giving a double linear appearance (railroad tracks); C3 was also present within the mesangium, outlining numerous circular structures (mesangial rings). By phase contrast, electron microscopy, and dual label fluorescence studies, the railroad tracks and mesangial rings were shown to outline dense deposit material. Mesangial rings contained properdin (four of nine patients); railroad tracks contained properdin (five of nine patients) and C4 (four of nine patients); no other complement components or immunoglobulins were present. Studies using rhodamine-conjugated rabbit antibody to human glomerular basement membrane demonstrated no reactivity with the dense deposit material itself. In type I and to a lesser extent in type II, granular deposits of C3, C4, properdin, IgM, and IgG were present along the glomerular basement membrane, suggesting that immune complexes play a role in both diseases. Dense deposit transformation of the glomerular basement membrane may be a consequence of a highly specific injury.