Postglomerular vascular protein concentration: evidence for a causal role in governing fluid reabsorption and glomerulotublar balance by the renal proximal tubule.

We tested the relationship between postglomerular microvascular protein concentration and rates of sodium and water transfer by rat proximal tubules. Using recently described microperfusion techniques, efferent arterioles and branch peritubular capillaries of normal hydropenic rats were perfused with colloid-free Ringer's solution, and isoncotic (9.0-10.0 g/100 ml) and hyperoncotic (15 g/100 ml) albumin-Ringer's solutions. Reabsorption in adjacent proximal tubules was studied using free-flow techniques, with initial collections obtained during normal blood perfusion, recollections during experimental microperfusion, and in some tubules, repeat recollections after microperfusion and spontaneous resumption of blood perfusion. Colloid-free perfusion resulted in a uniform inhibition of proximal reabsorption (absolute and fractional). Despite identical techniques, substitution of isoncotic and hyperoncotic perfusates resulted, on average, in unchanged and increased rates of reabsorption, respectively. These findings of direct linear changes in reabsorption in response to changes in postglomerular protein concentrations usually occurred in the absence of significant changes in filtered load, and were nearly always found to be reversible within minutes of cessation of experimental perfusion. Given this evidence of a causal relationship between postglomerular oncotic pressure and proximal reabsorption, we undertook to determine whether this relationship is responsible for the parallel adjustments in proximal reabsorption that follow changes in GFR (glomerulotubular balance). Using a separate group of hydropenic rats, proximal reabsorption was studied, initially during partial aortic constriction (during which renal perfusion pressure, single nephron GFR, absolute proximal reabsorption, and calculated filtration fraction all were reduced below levels prior to constriction), and again while adjacent efferent arteriolar and peritubular capillary protein concentrations, but not GFR, were restored to normal (preconstriction) levels by microperfusion with 9-10 g/100 ml albumin-Ringer's solution. During this dissociation of GFR and postglomerular protein concentration, absolute and fractional proximal reabsorption nearly always increased in parallel with the changes in the latter, thereby demonstrating that glomerulotubular balance is mediated, at least in part, by changes in postglomerular oncotic pressure brought about by changes in filtration fraction.

The dynamics of glomerular ultrafiltration in the rat.

Using a unique strain of Wistar rats endowed with glomeruli situated directly on the renal cortical surface, we measured glomerular capillary pressures using servo-nulling micropipette transducer techniques. Pressures in 12 glomerular capillaries from 7 rats averaged 60 cm H(2)O, or approximately 50% of mean systemic arterial values. Wave form characteristics for these glomerular capillaries were found to be remarkably similar to those of the central aorta. From similarly direct estimates of hydrostatic pressures in proximal tubules, and colloid osmotic pressures in systemic and efferent arteriolar plasmas, the net driving force for ultrafiltration was calculated. The average value of 14 cm H(2)O is lower by some two-thirds than the majority of estimates reported previously based on indirect techniques. Single nephron GFR (glomerular filtration rate) was also measured in these rats, thereby permitting calculation of the glomerular capillary ultrafiltration coefficient. The average value of 0.044 nl sec(-1) cm H(2)O(-1) glomerulus(-1) is at least fourfold greater than previous estimates derived from indirect observations.

On the mechanism of inhibition in fluid reabsorption by the renal proximal tubule of the volume-expanded rat.

We undertook to determine the extent to which the inhibition in absolute proximal fluid reabsorption in response to expansion of extracellular volume with noncolloid-containing solutions is the result of concomitant reductions in postglomerular (efferent arteriolar) protein concentration. Selective elevation of efferent arteriolar oncotic pressure in volume-expanded rats (Ringer's 10% body weight) to levels slightly in excess of normal by microperfusion with 9-10% albumin-Ringer's solution nearly completely reversed the inhibition in absolute and fractional reabsorption in adjacent proximal tubules. In contrast, during similar microperfusion with a 6-7% albumin solution, no increase in proximal reabsorption was measured. We interpret these findings to indicate that the bulk of the inhibition in absolute proximal reabsorption in response to volume expansion with colloid-free solutions is causally mediated by the accompanying parallel decline in postglomerular vascular protein concentration.

Evidence for a parathyroid hormone-dependent influence of calcium on the glomerular ultrafiltration coefficient.

Experiments were performed on 36 plasma-expanded Munich-Wistar rats to examine the effects of acute hypercalcemia on the determinants of glomerular ultrafiltration. Elevation of total plasma calcium concentration to an average value of 13.2 +/- 0.5 mg/dl, by acute infusion of calcium chloride into nonthyroparathyroidectomized (non-TPTX) rats, resulted in significant declines in single nephron and whole kidney glomerular filtration rate. These declines were due primarily to a fall in the glomerular capillary ultrafiltration coefficient (Kf), to a mean value approximately 60% below that determined in the pre-infusion period. These changes were not seen in a separate group of sham-treated non-TPTX rats. It is of interest that these effects of acute hypercalcemia were largely abolished in rats that underwent acute TPTX before hypercalcemia. Infusion of a submaximally phosphaturic dose of parathyroid hormone, together with calcium chloride, into a second group of acute TPTX rats, however, had the effect of reproducing the striking declines in filtration rate and Kf noted in non-TPTX rats given calcium chloride alone. These findings suggest that the decline in filtration rate associated with hypercalcemia is due largely to the reduction in Kf, the latter dependent upon the presence of parathyroid hormone.

Dynamics of glomerular ultrafiltration in the rat. IV. Determination of the ultrafiltration coefficient.

Pressures and flow rates were measured in accessible surface glomeruli of mutant Wistar rats under conditions deliberately designed to prevent achievement of filtration pressure equilibrium, that is, the equalization of transcapillary hydrostatic and oncotic pressures by the efferent end of the glomerulus as typically observed in the normal hydropenic rat. Disequilibrium was obtained at elevated levels of glomerular plasma flow (GPF) brought about by acute expansion of plasma volume with a volume of rat plasma equal to 5% of body weight. Glomerular hydrostatic and oncotic pressures measured at high GPF were used to calculate the ultrafiltration coefficient, K(f), the product of effective hydraulic permeability and surface area. GPF was then either lowered (by aortic constriction) or raised (by carotid occlusion) in order to examine the dependence of K(f) on GPF. The value of K(f) per glomerulus, 0.08 nl/(s.mm Hg), was found not to vary over an approximately twofold range of GPF. This finding, taken together with data from previous studies from this laboratory, leads us to conclude that plasma-flow dependence of glomerular filtration rate (GFR) results primarily from flow-induced changes in mean ultrafiltration pressure, rather than large changes in K(f).

Quantitative importance of changes in postglomerular colloid osmotic pressure in mediating glomerulotubular balance in the rat.

In recent studies in this laboratory employing normal hydropenic rats we have demonstrated that the reduction in absolute proximal reabsorption that attends the experimental reduction of single nephron glomerular filtration rate (SNGFR) (glomerulotubular balance) is mediated, at least in part, by the accompanying decline in postglomerular vascular protein concentration, and therefore, postglomerular colloid osmotic pressure (piEA). The present study was undertaken to define the quantitative contribution of these changes in piEA to the changes in absolute proximal reabsorption measured under these conditions. A protocol was employed which enabled us to examine the effects on absolute proximal reabsorption of reductions in filtered load brought about under conditions in which piEA remained essentially unchanged. Thus, after partial aortic constriction in 16 plasma-loaded rats, near constancy of piEA was observed in 10 (a change in efferent arteriolar protein concentration of 0.4 g/100 ml or less) and in these, uniform reductions in SNGFR averaging 16.7 nl/min were attended by reductions in absolute proximal reabsorption averaging only 1.7 nl/min, or 7% of preconstriction values. These findings, taken together with previous observations from this laboratory, suggest that the proximal reabsorptive adjustment that characterizes glomerulotubular balance in the rat is markedly blunted when changes in piEA are prevented. In the remaining six rats, a mean reduction in filtered load comparable to that observed in the above group was attended by slightly to moderately greater reductions in efferent arteriolar protein concentration, thereby fulfilling less well the stated aim of this study. Nevertheless, in accord with the above conclusion, these relatively greater reductions in piEA were accompanied by correspondingly greater reductions in absolute proximal reabsorption.

Mechanism of reduced glomerular filtration rate in chronic malnutrition.

To determine the physiological basis for the low glomerular filtration rate in chronic malnutrition, micropuncture studies were performed in Munich-Wistar rats chronically pair-fed isocaloric diets of either low (group 1, nine rats) or high protein content (group 2, nine rats). Despite the absence of hypoalbuminemia, average values for single nephron and total kidney glomerular filtration rate were nearly 35% lower in group 1 than in group 2. Mean values for glomerular capillary and Bowman's space hydraulic pressures were essentially identical in the two groups, thereby excluding glomerular transcapillary hydraulic pressure difference as the cause for the low filtration rates in group 1 animals. On the other hand, average glomerular capillary plasma flow rate and glomerular capillary ultrafiltration coefficient were significantly lower (by approximately 25 and approximately 50%, respectively) in group 1 than in group 2. The fall in glomerular capillary plasma flow rate was the consequence of increased afferent and efferent arteriolar resistances. Plasma and erythrocyte volumes were found to be equal in five additional pairs of group 1 and group 2 rats. Thus, the substantial alterations in the ultrafiltration coefficient, glomerular capillary plasma flow rate, and renal arteriolar resistances responsible for the low filtration rate in group 1 animals were not merely a consequence of decreased circulating blood or plasma volumes. Mean values for glomerular cross sectional area were significantly lower in group 1 than in group 2 despite similar values for kidney weight in the two groups. This reduction in glomerular cross sectional area in group 1 rats is presumed to reflect a decrease in effective filtration surface area and therefore likely accounts, at least in part, for the decline in ultrafiltration coefficient observed in this group.Finally, since the daily caloric intake of group 2 animals was restricted because of pair feeding requirements tied to the group 1 rats, we studied a third group of seven rats (group 3) allowed an ad lib. intake of the same high protein diet as given to group 2 rats. Average values for single nephron glomerular filtration rate and its determinants were found to be indistinguishable between groups 2 and 3. These results suggest that low protein intake, rather than calorie deficiency per se, is primarily responsible for the reduction in filtration rate seen in this experimental model of chronic malnutrition.

Mechanisms of the puromycin-induced defects in the transglomerular passage of water and macromolecules.

To investigate the mechanism(s) of increased filtration of serum proteins after glomerular injury, polydisperse samples of uncharged [(3)H]dextran (D) or anionic [(3)H]dextran sulfate (DS) were infused into 14 control and 16 puromycin aminonucleoside- (PAN) treated Munich-Wistar rats. Fractional clearances of D or DS ranging in radius from 18 to 42A were determined in these rats, together with direct measurements of the forces governing the glomerular filtration rate of water. Whole kidney and single nephron glomerular filtration rates were approximately 40% lower in PAN-treated rats, relative to controls, due mainly to a marked reduction in the glomerular capillary ultrafiltration coefficient and, to a lesser extent, to a small reduction in glomerular plasma flow rate as well. In PAN-treated rats, as in normal controls, inulin was found to permeate the glomerular capillary wall without measurable restriction, and both D and DS were shown to be neither secreted nor reabsorbed. Fractional clearances of uncharged D were reduced after PAN administration, falling significantly for effective D radii from 22 to 38A. Utilizing a theory based on macromolecular transport through pores, these results indicate that in PAN-treated rats, effective pore radius is the same as in controls, approximately 44A. In PAN nephrosis, however, the ratio of total pore surface area/pore length, a measure of pore density, is reduced to approximately one-third that of control, due very likely to a reduction in filtration surface area. In contrast to the results with uncharged D, fractional clearances of DS were found to increase after PAN administration for all DS radii studied. These results with D and DS suggest that proteinuria in PAN nephrosis is due, not to an increase in effective pore radius or number of pores, but rather to a diminution of the electrostatic barrier function of the glomerular capillary wall, thereby allowing increased passage of polyanions such as DS and albumin.

The role of complement in experimental bullous pemphigoid.

Bullous pemphigoid (BP) is a blistering skin disease associated with an IgG autoimmune response directed against the ectodomain of the hemidesmosomal protein, BP180. An animal model of BP has recently been developed by our laboratory based on the passive transfer of rabbit antimurine BP180 antibodies into neonatal BALB/c mice. The experimental animals develop a blistering disease that reproduces all of the key immunopathological features of BP. In the present study we have investigated the role of complement in the pathogenesis of subepidermal blistering in the mouse model of BP. We demonstrate the following. (a) Rabbit anti-murine-BP180 IgG was effective in inducing cutaneous blisters in a C5-sufficient mouse strain, but failed to induce disease in the syngeneic C5-deficient strain; (b) neonatal BALB/c mice, pretreated with cobra venom factor to deplete complement, became resistant to the pathogenic effects of the anti-BP180 IgG; (c) F(ab')2 fragments generated from the anti-BP180 IgG exhibited no pathogenic activity in the mouse model; and (d) histologic evaluation of the skin of mice described in points b and c above showed minimal or no neutrophilic cell infiltration in the upper dermis. Thus, anti-BP180 antibodies trigger subepidermal blistering in this BP model via complement activation. This experimental model of BP should greatly facilitate future studies on the pathophysiology of autoantibody-mediated diseases of the dermal-epidermal junction.

A passive transfer model of the organ-specific autoimmune disease, bullous pemphigoid, using antibodies generated against the hemidesmosomal antigen, BP180.

Subepidermal blistering associated with the human skin diseases bullous pemphigoid and herpes gestationis has been thought to be an IgG autoantibody-mediated process; however, previous attempts to demonstrate the pathogenicity of patient autoantibodies have been unsuccessful. An immunodominant and potentially pathogenic epitope associated with these blistering diseases has recently been mapped to the extracellular domain of a human epidermal antigen, BP180. Patient autoantibodies that react with this well-defined antigenic site failed to crossreact with the murine form of this autoantigen and thus could not be assayed for pathogenicity in a conventional passive transfer mouse model. As an alternative, rabbit polyclonal antibodies were generated against a segment of the murine BP180 protein homologous with the human BP180 autoantibody-reactive site and were passively transferred into neonatal BALB/c mice. The injected animals developed a subepidermal blistering disease that closely mimicked bullous pemphigoid and herpes gestationis at the clinical, histological, and immunological levels. Autoantibodies that recognize the human BP180 ectodomain are therefore likely to play an initiatory role in the pathogenesis of bullous pemphigoid and herpes gestationis.

Role for intrarenal mechanisms in the impaired salt excretion of experimental nephrotic syndrome.

A unilateral model of puromycin aminonucleoside (PAN)-induced albuminuria was produced in Munich-Wistar rats to examine the mechanisms responsible for renal salt retention. 2 wk after selective perfusion of left kidneys with PAN (n = 8 rats) or isotonic saline (control, n = 7 rats), increases in albumin excretion and decreases in sodium excretion were demonstrated in PAN-perfused but not in nonperfused kidneys of PAN-treated rats although systemic plasma protein concentration remained at control level. Total kidney glomerular filtration rate (GFR) and superficial single nephron (SN) GFR were also reduced selectively in PAN-perfused kidneys, on average by approximately 30%, due primarily to a marked decline in the glomerular capillary ultrafiltration coefficient (Kf), which was also confined to PAN-perfused kidneys. Values for absolute proximal reabsorption (APR) were also selectively depressed in PAN-perfused kidneys, in keeping with a similarly selective decline in peritubular capillary oncotic pressure measured in these kidneys, the latter also a consequence of the fall in Kf. In a separate group of seven PAN-treated rats, however, no differences were detected between PAN-perfused and nonperfused kidneys in the absolute amount of sodium reaching the early (0.77 +/- 0.09 neq/min vs. 0.74 +/- 0.08, P greater than 0.40) and late portions of superficial distal tubules (0.31 +/- 0.02) neq/min vs. 0.32 +/- 0.05, P greater than 0.50), despite the lesser filtered load of sodium in PAN-perfused kidneys. Suppressed sodium reabsorption in both proximal convoluted tubules and short loops of Henle of PAN-perfused kidneys contributed to this equalization of sodium delivery rates to the late distal tubule, as did comparable reabsorption along distal convolutions. In two additional groups of PAN-treated rats, infusion of saralasin (0.3 mg/kg per h, i.v.) led to substantial increases in total kidney GFR and SNGFR in PAN-perfused but not in nonperfused kidneys. Despite these increases in total and SNGFR, urinary sodium excretion by PAN-perfused kidneys remained at a level far below that for nonperfused kidneys, again indicating that the antinatriuresis characterizing the PAN-perfused kidney is due to alterations in sodium handling by the tubules rather than changes in GFR. These results therefore indicate (a) that reductions in Kf and depressed sodium reabsorption by proximal tubules and Henle's loop segments in this model are brought about by intrarenal rather than circulating or systemic factors, and (b) assuming that superficial nephrons are representative of the entire nephron population, renal salt retention in this model is due primarily to intrarenal factor(s) acting beyond the distal convolution.

A major role for neutrophils in experimental bullous pemphigoid.

Bullous pemphigoid (BP) is an inflammatory subepidermal blistering disease associated with an IgG autoimmune response to the hemidesmosomal protein, BP180. Using a passive transfer mouse model, our group has shown previously that antibodies to the murine BP180 (mBP180) ectodomain are capable of triggering a blistering skin disease that closely mimics human BP. In this study, we investigated the role of neutrophils in the immunopathogenesis of this disease model. BALB/c mice depleted of circulating neutrophils by treatment with neutrophil-specific antibodies were no longer susceptible to the pathogenic effects of anti-mBP180 IgG. IgG and complement were deposited at the dermal-epidermal junction of these animals, but there was no evidence of inflammatory infiltration or blistering. C5-deficient mice, which are resistant to the pathogenic activity of anti-mBP180 IgG, could be made susceptible to this IgG-mediated blistering disease by intradermal administration of a neutrophil chemoattractant, IL-8 or C5a. Intraperitoneal injection of IL-8, which sequesters neutrophils in the peritoneal cavity, interferes with anti-mBP180-induced neutrophilic infiltration of the skin and prevented the development of BP disease in BALB/c mice. These findings provide the first direct evidence that neutrophils recruited to the skin via a C5-dependent pathway play an essential role in subepidermal blister formation in experimental BP, and suggest new directions for disease intervention.

Permselectivity of of the glomerular capillary wall. Studies of experimental glomerulonephritis in the rat using neutral dextran.

Polydisperse [3h] dextran was infused into eight Munich-Wistar rats in the early autologous phase of nephrotoxic serum nephritis (NSN), thereby permitting direct measurements of pressures and flows in surface glomeruli and fractional clearances for dextrans [(U/P) dextran/(U/P) inulin] ranging in radius from 18 to 42 A. Despite glomerular injury, evidenced morphologically and by a marked reduction in the glomerular capillary ultrafiltration coefficient, the glomerular filtration rate remained normal because of a compensating increase in the mean net ultrafiltration pressure. In NSN rats, as in normal controls, inulin was found to permeate the glomerular capillary wall without measurable restriction, and dextrans were shown to be neither secreted nor reabsorbed. For dextran radii of 18, 22, 26, 30, 34, 38, and 42 A, (U/P) dextran/(U/P) inulin in NSN and control rats, respectively, averaged 0.90 vs. 0.99, 0.81 vs. 0.97, 0.63 vs. 0.83, 0.38 vs 0.55, 0.20 vs. 0.30, 0.08 vs. 0.11, and 0.02 vs. 0.03. Using a theory based on macromolecular transport through pores, the results indicate that in NSN rats, effective pore radius is the same as in controls, approximately 50 A. In NSN, however, the ratio of total pore surface area to pore length, a measure of the number of pores, is reduced to approximately 1/3 that of control, probably due to a reduction in capillary surface area. These results suggest that proteinuria in glomerular disease is not due simply to increases in effective pore radius or number of pores, as previously believed. Using a second theoretical approach, based on the Kedem-Katchalsky flux equations, dextran permeability across glomerular capillaries was found to be slightly lower, and reflection coefficient slightly higher in NSN than in control rats.

Permselectivity of the glomerular capillary wall. Studies of experimental glomerulonephritis in the rat using dextran sulfate.

To determine whether the increased filtration of serum proteins after glomerular injury is the consequence of altered electrostatic properties of the glomerular capillary wall, we measured fractional clearances of the anionic polymer, dextran sulfate, in nine Munich-Wistar rats in the early autologous phase of nephrotoxic serum nephritis (NSN). In agreement with previous studied from this laboratory, whole kidney and single nephron glomerular filtration rates were normal in NSN rats despite histological evidence of glomerular injury, and despite a marked reduction in the glomerular capillary ultrafiltration coefficient to approximately one-third of normal. In the companion study (9), it was shown that in NSN rats the mean fractional clearances of neutral dextrans over the range of effective molecular radii from 18 to 42 A were reduced, compared to normla. In contrast, in the present study the mean fractional clearances for dextran sulfate over the same range of molecular radii were significantly greater than those found previously for normal Munich-Wistar rats. The fractional clearance of dextran sulfate molecules of the same molecular radius as serum albumin (approximately 36 A) was increased markedly, from 0.015 +/- 0.005 (SEM) in nonnephritic controls to 0.24 +/- 0.03 in NSN (P less than 0.001). The sialoprotein content of glomeruli, estimated by the colloidal iron reaction, was reduced in NSN rats as compared to normal controls. It is concluded that the abnormal filtration of anionic serum proteins, such as albumin, seen in glomerulopathies is, at least in part, the consequence of loss of fixed negative charges from the glomerular capillary wall.

Influence of molecular configuration on the passage of macromolecules across the glomerular capillary wall.

The influence of molecular configuration on the filtration of macromolecules across glomerular capillary walls was examined by comparing fractional clearances of two uncharged polysaccharides of distinctly different molecular configuration in the Munich-Wistar rat. The macromolecules employed were dextran, a slightly branched polymer of glucopyranose, and ficoll, a highly cross-linked copolymer of sucrose and epichlorohydrin. Differences in effective shape between these two polymers were determined from measurements of several physical properties of aqueous solutions containing either dextran or ficoll. It was found that dextran is best represented as a prolate ellipsoid with axial ratios of 4, 9, and 16 for molecules with Stokes-Einstein radii of 22, 32, and 40 A, respectively. On the other hand, ficoll is more closely approximated as spherical since the axial ratio was found to be between 1 and 2 for all molecular sizes. Fractional clearances of dextran and ficoll ranging in effective radius from 18 to 44 A were determined in each of seven Munich-Wistar rats. Fractional clearances of dextran were found to be greater than those of ficoll, the difference being significant for molecular radii ranging from 24 to 44 A. In addition, as shown previously for dextran, ficoll was found to be neither secreted nor reabsorbed by the renal tubules. These results, therefore, suggest that in addition to molecular size and charge, molecular configuration is also a determinant of the filtration of macromolecules across the glomerular capillary wall.

The angiotensin receptor antagonist, irbesartan, reduces renal injury in experimental chronic renal failure.

The effects of chronic treatment with the specific AT1 angiotensin receptor antagonist, irbesartan, or the angiotensin converting enzyme inhibitor, enalapril, were assessed in uninephrectomized fawn-hooded hypertensive rats (FHH) and compared with vehicle treatment. Three days after uninephrectomy, irbesartan (240 mg/liter), enalapril (80 mg/liter) or vehicle were administered via the drinking water. Systolic blood pressure (SBP) and protein excretion rates (UprotV) were determined monthly. In rats receiving irbesartan (N = 7) and enalapril (N = 6) SBP (132 +/- 3 mm Hg and 133 +/- 6, respectively) was essentially normalized at 12 weeks when compared with vehicle (169 +/- 6 mm Hg (N = 6); all comparisons were P < 0.05 by ANOVA). Similarly, proteinuria was lower in irbesartan (44 +/- 12 mg/day) and enalapril (19 +/- 2) groups versus vehicle (123 +/- 10 mg/day). Treatment with both drugs was associated with marked reduction in glomerulosclerosis at 12 weeks (both < 5% vs. vehicle, 43 +/- 9%) without effect on glomerular volume. In identically prepared rats, glomerular capillary hydraulic pressure (PGC, estimated from stop-flow pressure, Psf) was lower in FHH receiving irbesartan (58 +/- 1 mm Hg, N = 6) or enalapril (54 +/- 2, N = 6) than in vehicle-treated rats, in whom PGC was greatly elevated (68 +/- 2 mm Hg; N = 7). Despite this, GFR and single nephron GFR were well maintained. These data support a critical role for AT1 receptor-mediated, angiotensin-dependent processes in the pathogenesis of hypertension in FHH, and further implicate elevated PGC as a major determinant of glomerular injury in this model.

Self-healing dystrophic calcinosis following trauma with transepidermal elimination.

An unusual case of dystrophic calcinosis that occurred following trauma is presented. Calcinosis cutis is the deposition of calcium phosphate into the skin. It is classified as dystrophic if calcium and phosphorous levels are normal and tissue damage is present, idiopathic if calcium and phosphorous levels are normal and no tissue damage is present, or metastatic if there is hypercalcemia or hyperphosphatemia. The numerous causes of underlying tissue damage associated with dystrophic calcinosis are discussed.

TCV 116 prevents progressive renal injury in rats with extensive renal mass ablation.

OBJECTIVE: The objective of this study was to determine the renal protective effects of TCV 116, a novel, non-competitive, angiotensin II type 1 (AT1) receptor antagonist, in rats with 5/6 renal mass ablation. DESIGN: Adult male Wistar rats were subjected to 5/6 nephrectomy and treated continuously with either TCV 116 (group I, n = 8; group III, n = 9) or vehicle (group II, n = 8; group IV, n = 8). The development of elevated systolic blood pressure, 24-h urinary protein excretion, glomerular hemodynamics and glomerular morphology were compared among groups. RESULTS: Systolic blood pressure rapidly reached hypertensive levels in group II, increasing from 175 +/- 8 mmHg after 3 weeks to 221 +/- 15 mmHg after 12 weeks, whereas group I rats remained normotensive (101 +/- 8 to 112 +/- 6 mmHg). Similarly, urinary protein excretion increased from 45 +/- 11 to 104 +/- 18 mg/day in group II, but remained low (6.9 +/- 1 to 19 +/- 4 mg/day) in group I. After 12 weeks, there was an average of 42 +/- 6% glomerulosclerosis in group II, but only 1.6 +/- 0.5% in group I. After 4-6 weeks, a markedly elevated glomerular capillary pressure (62 +/- 1.2 mmHg) was observed in group IV, but the pressure was normal in group III (50 +/- 1.1 mmHg). CONCLUSIONS: These data show that TCV 116 prevents the development of systemic hypertension, glomerular capillary hypertension, proteinuria and glomerulosclerosis in rats with reduced renal mass. We therefore conclude that the renal protection associated with angiotensin I converting enzyme inhibitors and other pharmacologic blockers of the renin-angiotensin system arises chiefly from blockade of AT1 receptor-mediated hemodynamic effects.

Candesartan cilexetil reduces chronic renal allograft injury in Fisher-->Lewis rats.

OBJECTIVES: To determine the effects of the angiotensin II receptor antagonist, candesartan cilexetil, on glomerular and systemic blood pressures and the development of renal injury in Lewis rat recipients of a single Fisher kidney (F334--> LEW transplantation), an established rat model of chronic renal allograft failure. DESIGN: Recent studies have shown that chronic injury of renal allografts in F334-->LEW rats may be virtually abrogated by supplying the Lewis recipients with two Fisher kidneys or, alternatively, by retaining a native kidney. These findings imply a major contribution from processes associated with nephron loss to the pathogenesis of chronic renal allograft failure, a notion supported by the observation that transplanting two kidneys also normalizes glomerular capillary pressure (PGC) in F344-->LEW rats. Thus, a pharmacological reduction in PGC, by blocking the effects of angiotensin II, should also lessen renal injury in F344-->LEW rats. MATERIALS AND METHODS: Bilaterally nephrectomized F344--> LEW rats were treated with the angiotensin II receptor blocker candesartan cilexetil (TCV-116) at 40 mg/l or with vehicle, administered in drinking water. Proteinuria and systolic blood pressure were assessed monthly, and histological studies were carried out after 24 weeks. The glomerular filtration rate and glomerular pressures were determined after 10 weeks in additional rats by clearance and micropuncture studies. RESULTS: Treatment with candesartan cilexetil lowered systemic blood pressure, normalized PGC at 10 weeks and greatly reduced proteinuria and allograft glomerulosclerosis at 24 weeks. CONCLUSIONS: These data indicate that the development of renal injury in F344-->LEW renal allografts can be prevented by the pharmacological blockade of angiotensin II receptors using candesartan cilexetil. This suggests that angiotensin-dependent processes contribute significantly to chronic injury in this model of late renal allograft failure.