Vascular endothelin-1 gene expression and synthesis and effect on renal type I collagen synthesis and nephroangiosclerosis during nitric oxide synthase inhibition in rats.
BACKGROUND: The progression of hypertension during NO deficiency is associated with renal vascular fibrosis due to increased extracellular matrix (mainly collagen I) formation. The purpose of the present study was to investigate whether endothelin-1 (ET-1) is involved in this pathophysiological process. METHODS AND RESULTS: Treatment of rats for 4 weeks with the NO synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME) 50 mg. kg-1. d-1 increased systolic blood pressure to 159+/-12 mm Hg. In animals treated with L-NAME, histological evaluation of renal sections revealed an increased formation of extracellular matrix (Masson's trichrome), and specifically of collagens (Sirius red). A part of this fibrosis was attributed to abnormal collagen I presence, because mRNA expression of the collagen I alpha1 chain (reverse transcription-polymerase chain reaction) and procollagen I formation (radioimmunoassay) were increased 3- and 2.5-fold, respectively, in the renal resistance vessels of hypertensive animals. In subsequent experiments, we examined whether ET-1 was involved in activation of collagen I formation. mRNA expression (RNase protection assay) of preproET-1 and ET-1 content (radioimmunoassay) were 10-fold and 3-fold increased, respectively, in renal microvessels of rats treated with L-NAME. Interestingly, in these vessels, ET-1 (immunostaining) was colocalized with sudanophilic lesions. Bosentan, an ET receptor antagonist (20 mg. kg-1. d-1), coadministered with L-NAME canceled the increased mRNA expression and synthesis of collagen I and attenuated the severity of renal vascular lesions without affecting L-NAME-induced high blood pressure. CONCLUSIONS: These data demonstrate that ET-1 synthesis is increased in renal microvessels when NO production is suppressed. In this model of hypertension, ET-1 is a major activator of collagen I formation in renal resistance vessels and participates in the development of renal fibrosis without affecting systolic blood pressure. (+info)
Heavy metal nephropathy of rodents.
Heavy metal nephropathy is a pathologic entity of the renal tubular epithelium of rats, evoked by lead, gold, and other heavy metals. It is characterized acutely by coagulative necrosis, subacutely by cortical fibrosis, and chronically by cytomegaly and karyomegaly. Finally, adenomas develop, some of which become malignant. (+info)
Strain differences of hypertension induced by dietary NG-nitro-L-arginine in normotensive rats.
When the potent inhibitor of nitric oxide (NO) synthesis NG-nitro-L-arginine (L-NNA) was incorporated into the diet, hypertension was induced and sustained due to the effects of the long-term inhibition of endothelium-dependent relaxing factor (EDRF)/NO. The effects of L-NNA on normotensive rats of four strains (Donryu, Sprague-Dawley (SD), Wistar, and Wistar-Kyoto (WKY)) were compared relative to control rats. L-NNA administration caused a sharp initial increase in systolic blood pressure (SBP) at 2 weeks in all animals, and this was followed by a gradual and steady increase until 4 weeks. At the end of the experiments (5 weeks), the mean SBP of Donryu and SD rats was decreased. The maximum blood pressure of Donryu and Wistar rats during the experiments exceeded 200 mmHg, but that of SD and WKY rats was below 200 mmHg. Body weight loss and death were observed only in L-NNA-fed Donryu rats. Pathological changes in the kidneys and the morbidity rates for the lesions were determined, and indicated that the Donryu L-NNA group was 100% positive. These results suggest that the Donryu strain is more sensitive to L-NNA than the other strains. That dietary L-NNA-induced hypertension in normotensive rats of the four strains provides a new artificially-induced hypertensive model in which vasoconstriction occurs mainly due to EDRF deficiency. (+info)
Disposition of [G-(3)H]paclitaxel and cremophor EL in a patient with severely impaired renal function.
In the present work, we studied the pharmacokinetics and metabolic disposition of [G-(3)H]paclitaxel in a female patient with recurrent ovarian cancer and severe renal impairment (creatinine clearance: approximately 20 ml/min) due to chronic hypertension and prior cisplatin treatment. During six 3-weekly courses of paclitaxel at a dose level of 157.5 mg/m(2) (viz. a 10% dose reduction), the renal function remained stable. Pharmacokinetic evaluation revealed a reproducible and surprisingly high paclitaxel area under the plasma concentration-time curve of 26.0 +/- 1.11 microM.h (mean +/- S.D.; n = 6; c.v. = 4.29%), and a terminal disposition half-life of approximately 29 h. Both parameters are substantially increased ( approximately 1.5-fold) when compared with kinetic data obtained from patients with normal renal function. The cumulative urinary excretion of the parent drug was consistently low and averaged 1.58 +/- 0.417% (+/- S.D.) of the dose. Total fecal excretion (measured in one course) was 52.9% of the delivered radioactivity, and mainly comprised known mono- and dihydroxylated metabolites, with unchanged paclitaxel accounting for only 6.18%. The plasma area under the plasma concentration-time curve of the paclitaxel vehicle Cremophor EL, which can profoundly alter the kinetics of paclitaxel, was 114.9 +/- 5.39 microl.h/ml, and not different from historic data in patients with normal or mild renal dysfunction. Urinary excretion of Cremophor EL was less than 0.1% of the total amount administered. These data indicate that the substantial increase in systemic exposure of the patient to paclitaxel relates to decreased renal metabolism and/or urinary elimination of polar radioactive species, most likely lacking an intact taxane ring fragment. (+info)
Effects of angiotensin inhibitors on renal injury and angiotensin receptor expression in early hypertensive nephrosclerosis.
Angiotensin converting enzyme inhibitors (ACEI) are known to inhibit the progression of established renal failure. The aim of this study was to compare the efficacy of an ACEI and an AT1 receptor antagonist (AT1R-Ant) in preventing the development of renal disease, at an early stage of hypertensive nephrosclerosis. SHRSP/Izm rats (n = 61) were treated from 10 wk until 22 wk with the ACEI delapril (40 mg/kg/d) or the AT1R-Ant candesartan cilexetil (1 mg/kg/d). Proteinuria, and structural/ultrastructural changes were assessed at 14 and 22 wk. Treatment with either agent resulted in reductions in blood pressure and cardiovascular hypertrophy. Neither proteinuria nor major renal histological changes were evident at 14 wk. At 22 wk, however, proteinuria accompanied by nephrosclerotic changes was seen in the untreated SHRSP/Izm. Treatment with either ACEI or AT1R-Ant resulted in similar reductions in proteinuria (untreated, 32.2 +/- 7.4; delapril-treated, 5.5 +/- 1.2; candesartan-treated, 3.9 +/- 0.3 mg/100 g/d). Prominent sclerosis of small-to-medium sized renal arteries was seen in the untreated SHRSP/Izm at 22 wk, but was similarly attenuated by the ACEI and AT1R-Ant. The glomerular ultrastructure was comparable between the two groups. No significant changes in renal AT1a or AT1b receptor subtype mRNA expression were seen throughout the course of the study. In contrast, a decrease in AT2 receptor mRNA was seen in the drug-treated groups at 14 wk but not at 22 wk. These results suggest that both ACEI and AT1R-Ant have similar efficacy in attenuating the onset of renal injury in early hypertensive nephrosclerosis, and that treatment with either agent is associated with a transient decrease in AT2 receptor mRNA expression. (+info)
Expression of decorin, biglycan, and collagen type I in human renal fibrosing disease.
BACKGROUND: The extracellular matrix proteoglycans decorin and biglycan may have a pathogenic role in renal fibrosing disease via regulation of the activity of growth factors, such as transforming growth factor-beta, and effects on collagen type I fibrillogenesis. The expression of decorin and biglycan in human glomerular diseases characterized by mesangial sclerosis is unknown. METHODS: Decorin, biglycan, and collagen type I were localized immunohistochemically in human renal biopsy cases of amyloidosis (N = 18), diabetic nephropathy (N = 11), fibrillary glomerulonephritis (N = 5), immunotactoid glomerulopathy (N = 5), light-chain deposition disease (N = 4), idiopathic mesangial sclerosis (N = 4), and nephrosclerosis (N = 6), and in morphologically normal tissues obtained from tumor nephrectomies (N = 8). Decorin and biglycan mRNA synthesis was evaluated by in situ hybridization. RESULTS: Decorin and biglycan protein were not identified in normal glomeruli. Decorin accumulated in amyloid deposits, but not in deposits of fibrillary glomerulonephritis or immunotactoid glomerulopathy. Biglycan weakly accumulated in amyloid deposits, and both decorin and biglycan weakly stained mesangial nodules in cases of morphologically advanced light-chain deposition disease and diabetic nephropathy. In all analyzed cases, irrespective of the underlying disease, decorin and biglycan accumulated in glomeruli in areas of fibrous organization of the urinary space and in areas of tubulointerstitial fibrosis. Biglycan, but not decorin, accumulated in the neointima of arteriosclerotic blood vessels. Decorin and biglycan mRNA synthesis was detected at sites of proteoglycan accumulation in glomeruli, interstitium, and neointima. Collagen type I colocalized with decorin and biglycan deposits. CONCLUSIONS: Differences in extracellular matrix proteoglycan composition may be diagnostically useful in distinguishing morphologically similar diseases. Distinct patterns of proteoglycan expression may be related to modulation of specific growth factor activity in different glomerular diseases. (+info)
What is 'nephrosclerosis'? lessons from the US, Japan, and Mexico.
BACKGROUND: Selected features of 'nephrosclerosis' can be quantitated morphometrically in renal histology at autopsy. Specimens are available from Japan, Mexico, and the US (blacks and whites). METHODS: Autopsies of men and women aged 15-79 years provided renal samples for paraffin sectioning. These were assembled in New Orleans for objective evaluation after standardized staining with PAS-Alcian blue and interspersion with each other. Obsolescence of glomeruli, interstitial fibrosis, fibroplastic intimal thickenings of arteries, and arteriolar hyalinization, as operationally defined, were measured by objective morphometry. RESULTS: Obsolescence of glomeruli and interstitial fibrosis displayed the expected correlation with arterial intimal fibroplasia, but failed to confirm any direct association with arteriolar hyalinization. Some of the variation of 'nephrosclerosis', within and between populations, cannot be fully explained by microvascular defects. CONCLUSIONS: Arterial intimal fibroplasia appeared to promote 'nephrosclerosis', in the sense of fibrous replacement of atrophied nephrons, but arteriolar hyalinization did not. Hyaline deposits in arterioles may offer little or no threat to the integrity of the affected nephrons. 'Nephrosclerosis' appears to be multifactorial; it may be, in part, a consequence of fibroplasia in microscopic arteries causing ischaemic injury to scattered nephrons, but may also be a confluence of basically separate conditions, only some of which are known. (+info)
Induction of apoptosis during development of hypertensive nephrosclerosis.
BACKGROUND: As the biology of programmed cell death, or apoptosis, is clarified, a role for this process in the pathophysiology of organ dysfunction and fibrosis has been hypothesized. Hypertensive nephrosclerosis represents an important cause of end-stage renal disease. One model of the progressive, noninflammatory, sclerotic renal lesion of hypertension is the Dahl/Rapp salt-sensitive rat, which was examined in this study. METHODS: Male, Dahl/Rapp salt-sensitive (SS) and Sprague-Dawley rats were placed on either 0.3 or 8.0% NaCl diets for three weeks. Blood pressure was determined, and the kidneys were harvested for histochemical analysis and to obtain total RNA for RNase protection assays and total protein for Western blotting. RESULTS: An increase in apoptosis in the glomerular and tubular compartments was observed only in kidneys of SS rats on the high-salt diet. These findings occurred at a time when renal function was markedly impaired and irreversible changes in renal morphology developed. Temporally associated with this increase in apoptosis was augmented expression of pro-apoptotic molecules that included Fas, Bax, and Bcl-XS. CONCLUSIONS: The inappropriate shift in expression of proteins that facilitate apoptosis in the nephron, along with ongoing cell death that manifested at a time when renal function was deteriorating, supported an important role for this process in development of hypertensive nephrosclerosis. (+info)