Abstract. In renal failure, parathyroid hormone (PTH) is not only involved in the genesis of disturbed calcium/phosphate metabolism and ostitis fibrosa; it is also a permissive factor in the genesis of hypertension, cardiovascular damage, and dyslipidemia. The allosteric activator of the calcium sensing receptor NPSR-568 (R-568) has been shown to reduce the serum intact PTH (iPTH) concentration in uremic rats. It was the purpose of this study in subtotally nephrectomized (SNX) rats to compare pharmacologic abrogation of secondary hyperparathyroidism by R-568 with parathyroidectomy (PTX). The effects on progression of renal failure, BP, and lipid and structural parameters of kidney and heart were studied. Four groups of male SD-rats were studied: (1) sham-operated ϩ vehicletreated rats (controls); (2) SNX ϩ vehicle-treated rats (SNX); (3) parathyroidectomized SNX ϩ vehicle-treated rats (SNXϩPTX); and (4) SNX ϩ calcimimetic R-568 -treated rats (SNXϩR-568). R-568 (50 mol/kg per d) was administered by gavage. Eight weeks after SNX, serum creatinine concentration, urinary albumin excretion, BP, and serum LDL-cholesterol concentration were significantly lower in both R-568 -treated and parathyroidectomized SNX compared with vehicletreated SNX. In addition, structural abnormalities of the kidney (glomerulosclerosis, tubulointerstitial changes) and the heart (interstitial fibrosis, capillary length density, arteriolar wall thickness) were significantly less pronounced than in vehicletreated SNX. It is concluded that in experimental renal failure abrogation of hyperparathyroidism by administration of a calcimimetic or PTX similarly attenuates progression of renal failure. Furthermore, it interferes with the development of cardiovascular risk factors and cardiac remodeling.Secondary hyperparathyroidism (sHPT) is a known complication of chronic renal failure. Elevated concentrations of parathyroid hormone (PTH) play a role not only in the pathogenesis of renal bone disease (1,2), but also in the development of cardiovascular risk factors such as disturbed lipid metabolism (3,4), glucose intolerance (5), and hypertension (6 -8). Parathyroidectomy (PTX) attenuates progression of renal failure in subtotally nephrectomized rats (SNX) on a high protein (9) or high phosphate (10,11) diet. sHPT is also known to play an important role in the development of structural abnormalities of the heart in renal failure, including left ventricular hypertrophy, interstitial fibrosis, and arteriolar wall thickening of the heart (7,(12)(13)(14).Allosteric activators of the calcium sensing receptor, e.g., NPSR-568 (R-568), reduce PTH secretion in rats or patients with primary and secondary hyperparathyroidism (15-20).There is no information on whether calcimimetics also affect abnormalities of uremia other than calcemia, phosphatemia (21), PTH concentrations (22), and skeletal abnormalities (17).Therefore, it was the purpose of this study to compare the effects of the calcimimetic R-568 and of parathyroidectomy on progression of renal failure, ...
These findings document that acetone soluble components in cigarette smoke aggravate glomerulosclerosis and tubulointerstitial damage in the renal ablation model. Renal injury induced by cigarette smoke condensate in this model is reversed by renal denervation. We conclude that cigarette smoke-induced renal damage is due, at least in part, to activation of the sympathetic nerve system.
Uremic cardiomyopathy of men and rodents is characterized by lower myocardial capillary supply that in rats could be prevented by central and peripheral blockade of the sympathetic nervous system. The underlying pathomechanisms remain largely unknown. We investigated whether alterations of cardiac vascular endothelial growth factor (VEGF) gene and protein expression were involved. In our long-term experiment, we analyzed whether VEGF gene and protein expression was altered in the heart of male Sprague-Dawley rats with either sham operation (sham, n=10) or subtotal nephrectomy (SNX, n=10). In our short-term experiment (17 sham, 24 SNX), the effect of a putative downregulation of sympathetic nervous activity by surgical renal denervation (interruption of renal afferent pathways) on cardiac gene expression of VEGF, flt-1, and flk-1 and on myocardial capillary supply was analyzed. In the long-term study, cardiac capillary supply and vascular endothelial growth factor gene and protein expression were significantly lower in SNX than in sham. In the short-term experiment, cardiac VEGF mRNA expression was significantly lower in untreated SNX (4,258±2,078 units) than in both sham groups (11,709±4,169 and 8,998±4,823 units); this decrease was significantly prevented by renal denervation (8,190±3,889, P<0.05). We conclude that cardiac VEGF gene and protein expression is reduced in experimental renal failure, and this may be considered as one potential reason for impaired myocardial adaptation under the situation of cardiac hypertrophy. The beneficial effect of sympathetic downregulation on cardiac structure and function in renal failure may be at least in part explained by increased cardiac VEGF gene expression.
Abstract. The effect of the orally highly bioavailable and specific endothelin A (ETA) receptor antagonist LU 135252 was assessed in a model of chronic renal allograft nephropathy. Kidneys of Fisher rats were orthotopically grafted to Lewis rats. Fisher autografts and kidneys after uninephrectomy served as controls. All animals received low-dose cyclosporin A (CsA; 1.5 mg/kg body wt) for 10 d after surgery. Allotransplanted animals were then randomized to receive standard diet or a diet designed to deliver 30 mg of LU 135252/kg body wt per d for 35 wk. BP was monitored telemetrically. Treatment with LU 135252 did not affect systolic or diastolic pressure. Indices of glomerulosclerosis (GSI), and tubulointerstitial and vascular damage were measured. Chronic transplant nephropathy was almost completely prevented by LU 135252 compared with untreated allografts or kidneys of uninephrectomized controls, i.e., GSI 0.7 ± 0.12 versus 1.6 ± 0.25 (P < 0.001) versus 0.7 ± 0.06 (P < 0.001). Allograft weight and serum creatinine were significantly lower in treated versus untreated animals. The results are consistent with the notion that ETA receptor-mediated events play a role in the genesis of chronic transplant nephropathy.
Background: Early glomerular hypertrophy and late glomerulosclerosis have been observed in rats fed high fructose diet (HFD), comparable with those of diabetic rats. Several studies suggest a role for nitric oxide (NO) in the pathogenesis of renal damage in diabetes. This study investigated the possible role of NO in the pathogenesis of HFD-induced glomerular changes. Methods: Three study protocols were adopted. In the first, 20 rats were divided into two groups to evaluate the effect of HFD on glomerular size and on the urinary excretion of NO. In the second, the glomerular size was evaluated in 40 rats divided into four groups receiving: (1) standard diet (SD); (2) HFD; (3) HFD + L-NAME, and (4) SD + L-NAME for 1 month. In the third, the renal expression of inducible enzyme (iNOS) was compared in 10 rats on HFD and in 10 controls after a 1-month diet. Results: The results showed: (1) increased urinary excretion of NO and glomerular size, both induced by HFD; (2) prevention by L-NAME of the HFD-increased glomerular size, and (3) increased iNOS expression in the kidneys of rats fed HFD. Conclusion: These results suggest a role for NO in the pathogenesis of the early renal changes induced by HFD.
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