RESUMEN
BACKGROUND: The long-term outcome of renal allografts is characterized by a progressive deterioration of renal function and graft loss. Our aim was to determine early glomerular functional abnormalities, before they become clinically apparent. METHODS: Glomerular hemodynamics and dextran sieving were characterized in 21 well-functioning cadaveric renal allograft recipients [normal glomerular filtration rate (GFR) and albumin excretion rate (AER), who also had a kidney biopsy with normal or minimal histological changes] and in 15 uninephrectomized kidney donors. Both groups were one to three years after transplantation or uninephrectomy. RESULTS: The GFR and renal plasma flow (RPF) were similar in both groups (62 +/- 3 vs. 63 +/- 4, and 343 +/- 26 vs. 334 +/- 21 mL/min/1.73 m2 for GFR and RPF, in cadaveric recipients vs. donors, respectively), the AER was normal in both groups, but the mean arterial pressure was higher in renal recipients (103 +/- 3 vs. 94 +/- 3 mm Hg in uninephrectomy controls, P < 0.05). Despite similar levels of overall glomerular function in the two groups, the dextran sieving curve was uniformly elevated in the renal allograft recipients versus uninephrectomy controls (P < 0.05 for dextrans 38 to 66 A). Using a log-normal glomerular pore-size distribution model to analyze potential mechanisms, the elevation in the dextran sieving curve resulted from a shift in the distribution of glomerular filtering pores to a larger size (mean glomerular pore size 46 +/- 2 vs. 43 +/- 2 A for uninephrectomy controls, P < 0.05), resulting in a larger fraction of filtrate volume permeating very large pores. By morphometric analysis, the thickness of the glomerular basement membrane was increased in kidney allograft as compared to 2-kidney biopsy controls (614 +/- 33 vs. 427 +/- 22 nm, respectively, P < 0.05). CONCLUSIONS: Even in "well functioning" renal allografts there is a glomerular dysfunction characterized by increased permeability to macromolecules resulting from a shift of the glomerular pores to a larger size. These changes could be mediated by ultrastructural alterations at the glomerular capillary or by alterations in intraglomerular hemodynamics. Early allograft dysfunction may contribute to the progressive renal insufficiency of renal allografts.
Asunto(s)
Glomérulos Renales/fisiopatología , Trasplante de Riñón , Adolescente , Adulto , Anciano , Femenino , Tasa de Filtración Glomerular , Humanos , Masculino , Persona de Mediana Edad , Trasplante HomólogoRESUMEN
BACKGROUND: Leukotrienes are 5-lipoxygenated (5-LO) metabolites of arachidonic acid that mediate some of the glomerular hemodynamic and structural changes in experimental and human glomerulonephritis. METHODS: We conducted an open-label, pilot study of the short-term effects of leukotriene biosynthesis inhibition using an orally active 5-LO activating protein (FLAP) antagonist (MK-591) on glomerular function in patients with glomerulonephritis. Eleven adult patients (seven women, median age 38 years) with glomerulonephritis (5 lupus nephritis, 2 IgA nephropathy, 1 membranoproliferative, 1 membranous, 1 C1q-deficiency, and 1 idiopathic crescentic) and moderate renal insufficiency [glomerular filtration rate (GFR) 62 +/- 9 ml/min/1.73 m2] were given MK-591 at a dose of 100 mg orally twice a day for four days. RESULTS: MK-591 reduced proteinuria (albumin and IgG excretion rates) from 3233 +/- 1074 to 1702 +/- 555 microg/min and from 196 +/- 78 to 148 +/- 55 microg/min for albumin and IgG, respectively (P < 0.05 for both). This was not accompanied by a reduction in systemic arterial pressure, GFR, or renal plasma flow. By analysis of the fractional clearance of polydisperse dextrans, baseline proteinuria resulted from a loss of size selectivity with enhanced passage of large (>52 A) dextrans as compared with healthy controls. Treatment with MK-591 caused a selective improvement in the enhanced passage of large (>58 A) dextrans without affecting the handling of smaller dextrans, indicating an improvement in glomerular size selectivity. MK-591 was well tolerated, and no adverse effects were observed. CONCLUSIONS: Short-term therapy with MK-591 reduces proteinuria by restoring glomerular size selectivity and thus reduces transglomerular protein trafficking. These benefits may result from glomerular leukotriene biosynthesis inhibition, but other MK-591-specific actions cannot be excluded.
Asunto(s)
Glomerulonefritis/tratamiento farmacológico , Glomerulonefritis/metabolismo , Indoles/uso terapéutico , Glomérulos Renales/efectos de los fármacos , Glomérulos Renales/metabolismo , Inhibidores de la Lipooxigenasa/uso terapéutico , Proteinuria/orina , Quinolinas/uso terapéutico , Adulto , Anciano , Femenino , Glomerulonefritis/orina , Humanos , Indoles/efectos adversos , Inhibidores de la Lipooxigenasa/efectos adversos , Masculino , Persona de Mediana Edad , Permeabilidad , Proyectos Piloto , Proteinuria/etiología , Quinolinas/efectos adversos , Resultado del TratamientoRESUMEN
There is a large variability in the severity of the clinical manifestations of sickle cell anemia (SSA), including renal involvement. Haplotypes in the beta-globin gene cluster associated with the geographical origin of the sickle mutation, as well as microdeletions in the alpha-globin genes, could provide an epigenetic influence on the heterogeneous outcome in SSA. It has been determined that the cause of progressive renal insufficiency in SSA is a glomerulopathy, clinically detected by the presence of macroalbuminuria (albumin excretion rate >300 mg/g creatinine). To investigate the role of the alpha-globin gene microdeletion and beta-globin gene cluster haplotypes on the degree of glomerular involvement, 76 adult SSA patients (hemoglobin SS) were studied to determine the relationship between these genetic markers and the development of sickle cell glomerulopathy. Macroalbuminuria was present in 22 (29%) of 76 adult SSA patients. The coinheritance of microdeletions in one or two of the four alpha-globin genes (alpha-thalassemia) was associated with a lower prevalence of macroalbuminuria (13%) versus patients with intact alpha-globin genes (40%, P = 0.01). By contrast, there was no association between albuminuria and beta-globin gene haplotypes (Central African Republic [CAR] versus non-CAR haplotypes). Patients with alpha-globin gene microdeletions had lower mean corpuscular volumes and mean corpuscular hemoglobin concentration than patients with all four alpha genes (86+/-2 versus 99+/-3 fl, and 33.9+/-0.2 versus 34.9+/-0.2%, respectively, P<0.05). There were no such hematologic differences between CAR and non-CAR beta-globin haplotypes. There were no differences in duration of disease (age), hemoglobin levels, reticulocyte index, and lactate dehydrogenase levels between those with and without glomerulopathy, but the mean arterial pressure was higher (87+/-1 mm Hg) in patients with intact alpha gene locus versus those with microdeletions (80+/-2 mm Hg, P<0.05). It is concluded that the coinheritance of microdeletions in the alpha-globin gene locus in SSA patients confers "renoprotection" by mechanisms not related to the degree of anemia or the severity of hemolysis, but could be related to a reduced mean corpuscular volume or to a lower erythrocyte hemoglobin concentration.
Asunto(s)
Anemia de Células Falciformes/complicaciones , Eliminación de Gen , Globinas/genética , Enfermedades Renales/genética , Enfermedades Renales/prevención & control , Glomérulos Renales , Adulto , Albuminuria/epidemiología , Albuminuria/etiología , Anemia de Células Falciformes/sangre , Índices de Eritrocitos , Femenino , Marcadores Genéticos , Haplotipos/fisiología , Humanos , Masculino , Persona de Mediana Edad , Familia de Multigenes/genética , PrevalenciaRESUMEN
Hypertension is a common finding in non-insulin-dependent diabetes mellitus (NIDDM) nephropathy. African Americans have a high prevalence of NIDDM and hypertension, and are relatively resistant to the antihypertensive effects of converting enzyme inhibitors (CEI) but respond well to calcium channel blockers (CCB). In the long-term study presented here, the effects of isradipine, a dihydropyridine calcium antagonist, on the course of the nephropathy were investigated and compared with the effects of captopril in 31 African Americans with NIDDM and proteinuria (> or = 500 mg/day). The patients were stratified by levels of GFR and proteinuria, and they were randomized to receive isradipine (N = 16) or captopril (N = 15); doses were adjusted to maintain similar BP levels (< 140/90). At 6 months, mean arterial pressure was similar (102 +/- 3 and 104 +/- 3 mm Hg in the isradipine and captopril groups, respectively) and GFR was unchanged (delta = -4 +/- 3 and +1 +/- 3 ml/min/1.73 in the isradipine and captopril groups, respectively; P = NS). However, proteinuria in the isradipine group increased by approximately 50% (2.01 +/- 0.40 versus 3.04 +/- 0.70 mg/mg creatinine at baseline versus 6 months, respectively, P < 0.05), whereas captopril reduced proteinuria by 30% after 6 months (2.85 +/- 0.70 at baseline versus 2.30 +/- 0.70 mg/mg creatinine, P < 0.05). Dietary protein, sodium intake, and HbA1C levels were similar in both groups and did not differ from baseline. It was concluded that over 6 months, captopril reduces and isradipine increases proteinuria in African Americans with NIDDM and nephropathy. Whether this contrasting effect on proteinuria will result in different rates of progression is not known, but dihydropyridine CCB should be used cautiously in African Americans with diabetic nephropathy.