RESUMEN
Periostin, a recently found matricellular protein, has been implicated in neointima formation after balloon injury. However, the relationship between periostin and hyperplastic intima formation after PTFE graft implantation is unclear. Under mixed anesthesia, PTFE grafts were implanted between the canine carotid artery and jugular vein, and PTFE graft samples were harvested 1, 2, and 4 months after implantation. Intima formation started on the luminal surface of PTFE grafts at the venous anastomotic region 1 month after implantation. Thereafter, the increase in intimal volume was not only observed in the venous and arterial anastomotic regions, but also in the middle region of the PTFE grafts. In accordance with the increased intimal formation, time-dependent increases in mRNA expressions of periostin and transforming growth factor beta 1 (TGF-ß1), as well as a strong positive correlation between periostin and TGF-ß1, were observed. These findings suggest that periostin may play a very important role in the pathogenesis of hemodialysis vascular access stenosis through the acceleration of intimal formation. Thus, periostin may be a very important therapeutic target for the treatment of vascular access graft dysfunction in hemodialysis patients.
Asunto(s)
Prótesis Vascular , Moléculas de Adhesión Celular/metabolismo , Constricción Patológica/etiología , Diálisis Renal/efectos adversos , Animales , Biomarcadores , Prótesis Vascular/efectos adversos , Moléculas de Adhesión Celular/genética , Perros , Inmunohistoquímica , Politetrafluoroetileno , Diálisis Renal/métodos , Factor de Crecimiento Transformador beta/genética , Factor de Crecimiento Transformador beta/metabolismoRESUMEN
Cell adhesion molecule 1 (CADM1) is an immunoglobulin superfamily member strongly expressed on renal tubular epithelia in the urinary tract. Enzymatic cleavage of its ectodomain increases in chronic kidney disease (CKD), and is assumed to contribute to tubulointerstitial lesion formation. Because the cleaved ectodomain fragments are likely to be released into the urine, a sandwich enzyme-linked immunosorbent assay (ELISA) system for urinary CADM1 was developed using two anti-ectodomain antibodies. Urinary CADM1 concentrations in patients with CKD based on various forms of glomerulonephritis and nephropathy (n = 127) were measured. A total of 44 patients (35%) had elevated CADM1 concentrations over the normal upper limit (362 pg/mL), with a mean of 1,727 pg/mL. Renal biopsy specimens of all patients were pathologically scored for tubulointerstitial lesions using epithelial degeneration, interstitial inflammation, and fibrosis. There were no correlations between urinary CADM1 concentrations and pathological scores or any widely used renal markers, including glomerular filtration rate (GFR), but there was a weak inverse correlation between pathological scores and GFR (R2 = 0.292). Notably, this correlation gradually increased in patients with increasing CADM1 concentrations, and reached a maximum R 2 (0.899) at a cutoff of 1,569 pg/mL. The results of this study suggest that urinary CADM1 is a useful marker indicating tubulointerstitial damage from elevated GFR levels in CKD.
RESUMEN
We examined the potential contributions of oxidative stress and thromboxane A2 (TXA2) to the development of regional heterogeneity in hypertensive glomerular injury using stroke-prone spontaneously hypertensive rats (SHRSP), an animal model of human essential hypertension. We also examined the effect of antioxidant treatment on the regional expression of thromboxane synthase (TXAS) mRNA using a microdissection method. Increases in the glomerular expression of TXAS mRNA were observed in the SHRSP at 15 weeks of age compared with those in the age-matched normotensive control Wistar-Kyoto (WKY) rats: 2.4-fold and 3.1-fold in the superficial and juxtamedullary glomeruli, respectively (P < 0.05). The heme oxygenase-1 mRNA expression was markedly increased (greater than eightfold, P < 0.05) in both the superficial and juxtamedullary glomeruli in the SHRSP compared with the expression in the WKY rats. In contrast to our expectations, the treatment of SHRSP with tempol (a superoxide dismutase mimetic) significantly (P < 0.05) increased the TXAS mRNA expression in the superficial glomeruli and did not improve the histological injury or albuminuria, which were both aggravated. Moreover, ozagrel (a TXAS inhibitor) had a suppressive effect on the TXAS mRNA expression and significantly (P < 0.05) improved the histological injury. These results indicated that although TXA2 and oxidative stress are linked to each other, TXA2 rather than oxidative stress may be a better therapeutic target to improve hypertensive glomerular injury.
Asunto(s)
Hipertensión/metabolismo , Glomérulos Renales/metabolismo , Estrés Oxidativo/fisiología , Tromboxano A2/metabolismo , Tromboxano-A Sintasa/metabolismo , Animales , Presión Sanguínea , Hemo-Oxigenasa 1/metabolismo , Masculino , Ratas , Ratas Endogámicas SHR , Ratas Endogámicas WKYRESUMEN
We here report a case of nivolumab-induced acute granulomatous tubulointerstitial nephritis in a patient with gastric cancer. A 68-year-old woman with recurrent gastric cancer developed acute kidney injury associated with kidney enlargement and urinary leukocytes after 38 cycles of nivolumab treatment. A diagnosis of acute granulomatous tubulointerstitial nephritis was made based on kidney biopsy findings. Immunohistochemistry revealed expression of programmed cell death-ligand 1 (PD-L1) in degenerated epithelial cells of collecting tubules. Among infiltrating immune cells, aggregation of T cells was more extensive than that of B cells, with CD4+ T cells outnumbering CD8+ T cells, consistent with the relative numbers of these cells in the circulation. Treatment with methylprednisolone (1.0 mg/kg daily) led to a rapid improvement in renal function and reduction in the number of circulating CD4+ T cells. Prompt administration of high-dose corticosteroid is thus recommended after diagnosis of this adverse event of nivolumab treatment by kidney biopsy.
Asunto(s)
Antineoplásicos Inmunológicos/efectos adversos , Antineoplásicos Inmunológicos/uso terapéutico , Nefritis Intersticial/inducido químicamente , Nivolumab/efectos adversos , Nivolumab/uso terapéutico , Neoplasias Gástricas/tratamiento farmacológico , Anciano , Femenino , HumanosRESUMEN
Cryoglobulinemia can induce systemic vasculitis affecting various organs such as skin, peripheral nerves, and kidney. The disease can induce chronic organ failure and even be life-threatening. Cryofiltration has been applied for the treatment of cryoglobulinemic vasculitis. We have experienced four cases with mixed cryoglobulinemia showing severe and progressive clinical manifestations, including skin purpura, nephrotic syndrome, acute kidney injury, and peripheral neuropathy. Cryofiltration in conjunction with conventional pharmacological therapies appeared to be safe and effective. After the treatments, plasma cryoglobulins were markedly reduced and the disease was well controlled. Although its efficacy has not yet been well established, this report can be another evidence showing efficacy of cryofiltration for treatment of mixed cryoglobulinemia.
Asunto(s)
Crioglobulinemia/terapia , Crioglobulinas/metabolismo , Plasmaféresis/métodos , Vasculitis Sistémica/terapia , Adulto , Anciano , Crioglobulinemia/complicaciones , Crioglobulinemia/fisiopatología , Progresión de la Enfermedad , Filtración/métodos , Humanos , Masculino , Persona de Mediana Edad , Índice de Severidad de la Enfermedad , Vasculitis Sistémica/etiología , Resultado del TratamientoRESUMEN
Essential hypertension is a disease of unknown pathogenesis, although renal function has been implicated as an important factor in its cause. Stroke-prone spontaneously hypertensive (SHRSP) rats provide an animal model of essential hypertension. To understand the cause of hypertension, identifying proteins that are differentially expressed between hypertensive and normotensive rats may provide a key. Here, proteins in the renal cortex from SHRSP rats, malignant stroke-prone spontaneously hypertensive (M-SHRSP) rats, and Wistar Kyoto (WKY) rats as a normotensive control were subjected to two-dimensional difference gel electrophoresis (2D-DIGE). After in-gel digestion by trypsin, proteins were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). Several proteins showed differential expression patterns between hypertensive and normotensive rats. Among them, we focused on catechol-O-methyltransferase (COMT) because this enzyme inactivates catecholamines, possibly affecting blood pressure. To confirm the differential expression of COMT in each animal, we conducted Western blot analysis, which revealed that the expression of COMT is lower in M-SHRSP rats than in control and SHRSP rats, indicating that blood pressure and expression of COMT are related. In fact, the blood pressure of M-SHRSP rats was significantly higher than that of SHRSP rats at age of 10 weeks. Immunohistochemical and immunofluorescence studies showed that COMT in renal cortex is localized in tubular epithelial cells. The expression of COMT is lower in the renal cortex tubular epithelium of M-SHRSP rats than in normotensive rats. These results suggest that the decreased expression of COMT may be an important factor leading to the development of hypertension.
Asunto(s)
Catecol O-Metiltransferasa/metabolismo , Corteza Renal/enzimología , Corteza Renal/patología , Animales , Presión Sanguínea , Western Blotting , Electroforesis en Gel Bidimensional , Fluorescencia , Inmunohistoquímica , Corteza Renal/fisiopatología , Masculino , Ratas , Ratas Endogámicas SHR , Ratas Endogámicas WKY , Fracciones Subcelulares/enzimologíaRESUMEN
The plasma level of adiponectin, which is known as an anti-atherogenic adipocytokine, correlates inversely with the progression of atherosclerosis. An increase in the serum adiponectin level has been reported after the administration of hydrophilic pravastatin, but not after the administration of lipophilic statins thus far. We investigated whether hydrophilic pravastatin acts distinctly from simvastatin, which has the highest lipophilicity, on the favorable effect on adiponectin in dyslipidemic patients. A total of 27 dyslipidemic patients with mild hypertension were enrolled in this study. The patients were initially treated with simvastatin 10 mg/day for six months or more (mean 7.1 months), and then were switched to pravastatin 20 mg/day. The serum adiponectin, cholesterol fractionated components, and C-reactive protein (CRP) were evaluated after six-month intervals. Switching from simvastatin to pravastatin caused little change in the low-density lipoprotein cholesterol levels (103 mg/dl to 104 mg/dl, p = 0.782) and blood pressure (133/70 mmHg to 132/69 mmHg), while the serum adiponectin level significantly increased (11.9 mug/ml to 13.1 mug/ml, p = 0.009, respectively), and the serum CRP significantly decreased (0.078 mg/dl to 0.062 mg/dl, p = 0.040, respectively). Hydrophilic pravastatin increased the serum adiponectin level and decreased the CRP after switching from lipophilic simvastatin in the absence of any difference in the low-density lipoprotein cholesterol level and blood pressure. It remains possible, however, that this difference was due not only to pharmacologic lipophilicity, but also to some other specific characteristics such as the formula of statins, the subject characteristics, race, body size, high-density lipoprotein cholesterol, etc.
Asunto(s)
Dislipidemias/sangre , Dislipidemias/tratamiento farmacológico , Inhibidores de Hidroximetilglutaril-CoA Reductasas/farmacología , Hipertensión/sangre , Hipertensión/tratamiento farmacológico , Adiponectina/sangre , Tejido Adiposo/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Proteína C-Reactiva/metabolismo , Colesterol/sangre , Dislipidemias/complicaciones , Femenino , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Inhibidores de Hidroximetilglutaril-CoA Reductasas/química , Inhibidores de Hidroximetilglutaril-CoA Reductasas/farmacocinética , Hipertensión/complicaciones , Masculino , Persona de Mediana Edad , Pravastatina/química , Pravastatina/farmacocinética , Pravastatina/farmacología , Estudios Prospectivos , Simvastatina/química , Simvastatina/farmacocinética , Simvastatina/farmacologíaRESUMEN
There is increasing evidence for the pathophysiological importance of aldosterone in renal diseases. Studies have so far demonstrated that aldosterone exerts deleterious renal effects by inducing oxidative stress, endothelial dysfunction, inflammation and fibrosis through a mineralocorticoid receptor (MR)-dependent genomic mechanisms. On the other hand, a number of recent studies provided evidence that aldosterone can act through a rapid non-genomic mechanism in cardiovascular tissues including the kidney, though the relative importance of such actions in renal diseases remains to be determined. We have recently found that physiological concentrations of aldosterone cause rapid vasoconstriction in the renal microcirculation. The vasoconstrictor actions were compatible with non-genomic; the major characteristics was its relatively early onset (apparent within 5min), which was not affected by either actinomycin D or cycloheximide (inhibitors of transcription or protein synthesis). Thus, in addition to genomic actions, such non-genomic vasoconstrictor actions in the renal microcirculation may contribute to the deleterious renal effects of aldosterone in renal diseases.
Asunto(s)
Aldosterona/farmacología , Riñón/irrigación sanguínea , Resistencia Vascular/efectos de los fármacos , Vasoconstricción/efectos de los fármacos , Vasoconstrictores/farmacología , Aldosterona/fisiología , Animales , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/fisiopatología , Genoma , Humanos , Riñón/fisiopatología , Microcirculación , Antagonistas de Receptores de Mineralocorticoides/farmacología , Resistencia Vascular/fisiología , Vasoconstricción/fisiologíaRESUMEN
Recent studies provide evidence that aldosterone (Aldo) accelerates hypertension, proteinuria and glomerulosclerosis in animal models of chronic renal failure. Although the underlying mechanisms are not well defined, Aldo may exert these deleterious renal effects by elevating renal vascular resistance (RVR) and glomerular capillary pressure (P(GC)). To test this possibility, we studied the action of Aldo on rabbit afferent (Af-) and efferent arterioles (Ef-Arts), crucial vascular segments to the control of glomerular hemodynamics. Aldo caused rapid (within 5 min) constriction in both arterioles. The constriction was not affected by spironolactone but was reproduced by membrane-impermeable albumin-conjugated Aldo, suggesting that vasoconstrictor actions are non-genomic. This notion was further supported by the finding that neither actinomycin D nor cycloheximide had effect. The vasoconstrictor action of Aldo on Af-Arts was inhibited by nifedipine (L-type calcium channel blocker), whereas that on Ef-Arts was inhibited by efonidipine (both L- and T-type calcium channel blocker) but not nifedipine. Disrupting the endothelium or nitric oxide (NO) synthesis inhibition augmented the vasoconstriction in Af-Arts, demonstrating that endothelium-derived NO modulates the vasoconstrictor actions of Aldo. Thus, Aldo causes non-genomic vasoconstriction via calcium mobilization thorough L- or T-type calcium channels in Af- or Ef-Arts, respectively. These vasoconstrictor actions on the glomerular microcirculation may play an important role in the pathophysiology and progression of renal diseases by elevating RVR and P(GC), especially when endothelium functions are impaired. In addition to our study, this review describes recent findings on the rapid cardiovascular actions of Aldo, with a particular attention to the renal hemodynamics.
Asunto(s)
Aldosterona/fisiología , Riñón/irrigación sanguínea , Riñón/metabolismo , Animales , Humanos , Microcirculación/fisiología , Circulación Renal/fisiologíaRESUMEN
We have recently demonstrated that aldosterone causes nongenomic vasoconstriction by activating phospholipase C (PLC) in the preglomerular afferent arteriole (Af-Art). In the present study, we tested the hypothesis that endothelium modulates this vasoconstrictor action by releasing nitric oxide (NO). In addition, to study the post-PLC mechanism, we examined possible contributions of phosphoinositol hydrolysis products. Rabbit Af-Arts were microperfused at 60 mm Hg in vitro, and increasing doses of aldosterone (10(-10) to 10(-8) mol/L) were added to the bath and lumen. Aldosterone caused dose-dependent vasoconstriction (within 10 minutes); significant (P<0.01) constriction was observed from 5x10(-9) mol/L, and at 10(-8) mol/L, intraluminal diameter decreased by 29%+/-3% (n=9). Disrupting the endothelium augmented vasoconstriction; significant constriction was observed from 10(-10) mol/L, and at 10(-8) mol/L, the diameter decreased by 38%+/-2% (n=6). NO synthesis inhibition reproduced this augmentation (n=7). Pretreatment with chelerythrine (10(-6) mol/L), a protein kinase C (PKC) inhibitor, slightly attenuated the constriction; aldosterone at 10(-8) mol/L now decreased the diameter by 18%+/-3% (n=7). However, in Af-Arts treated with thapsigargin (10(-6) mol/L) or dantrolene (3x10(-5) mol/L), which blocks inositol 1,4,5-triphosphate (IP3)-induced intracellular calcium release, aldosterone at 10(-8) mol/L decreased the diameter by only 9%+/-1% (n=6) or 9%+/-2% (n=5), respectively. These results demonstrate that in the Af-Art endothelium-derived NO modulates vasoconstrictor actions of aldosterone that are mediated by the activation of both IP3 and PKC pathways. Such vasoconstrictor actions of aldosterone may contribute to the development or aggravation of hypertension by elevating renal vascular resistance in cardiovascular diseases associated with endothelium dysfunction.
Asunto(s)
Aldosterona/farmacología , Endotelio Vascular/fisiología , Riñón/irrigación sanguínea , Óxido Nítrico/fisiología , Vasoconstrictores/farmacología , Animales , Arteriolas/anatomía & histología , Arteriolas/efectos de los fármacos , Arteriolas/fisiología , Calcio/metabolismo , Endotelio Vascular/metabolismo , Masculino , Óxido Nítrico/biosíntesis , Proteína Quinasa C/antagonistas & inhibidores , Conejos , VasodilataciónRESUMEN
Hepatocyte growth factor (HGF) has recently been the focus of attention due to its angiogenic effects, which are similar to those of vascular endothelial growth factor (VEGF); because of these effects, HGF is considered to be a novel therapeutic agent against vascular disorders, including atherosclerotic angiopathies. Although nitric oxide (NO), which is derived from vascular endothelial cells (ECs), is also involved in angiogenesis, little is known regarding the interactions between HGF and NO. We therefore examined the effects of HGF on NO production as well as endothelial NO synthase (eNOS) phosphorylation, and investigated their mechanisms. In bovine aortic ECs, HGF induced a rapid (5 min) increase of NO production measured by diaminofluorescein-2 diacetate. Moreover, HGF rapidly (2.5 min) stimulated eNOS phosphorylation (Ser-1179) as determined by Western immunoblot analyses. Both of these effects were almost completely suppressed by the phosphoinositide 3-kinase (PI3K) inhibitor LY294002, and were partially suppressed by the mitogen-activated protein kinase (MAPK) kinase 1/2 inhibitor U0126. HGF also stimulated Akt phosphorylation (Ser-473), which was completely suppressed by LY294002 and was partially suppressed by U0126. Moreover, HGF stimulated extracellular signal-regulated kinase 1/2 phosphorylation (Thr-202/Tyr-204), which was completely suppressed by U0126 and was partially suppressed by LY294002. Taken together, these results indicate that HGF not only phosphorylates eNOS through the PI3K/Akt pathway, but also partially through the MAPK pathway, and that these two pathways may interact. Compared with VEGF, HGF was more potent in both NO production and eNOS phosphorylation. Our study thus demonstrates a novel activity of HGF-the stimulation of NO production-which occurs via eNOS phosphorylation that may in turn be mediated by cross-talk between the PI3K/Akt and MAPK pathways.
Asunto(s)
Células Endoteliales/efectos de los fármacos , Células Endoteliales/enzimología , Factor de Crecimiento de Hepatocito/farmacología , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Óxido Nítrico Sintasa/metabolismo , Animales , Aorta/citología , Bovinos , Células Cultivadas , Fluoresceína , Humanos , Indicadores y Reactivos , Sistema de Señalización de MAP Quinasas/fisiología , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Óxido Nítrico/metabolismo , Óxido Nítrico Sintasa de Tipo III , Fosfatidilinositol 3-Quinasas/metabolismo , Fosforilación/efectos de los fármacos , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-akt , Serina/metabolismo , Factor A de Crecimiento Endotelial Vascular/farmacologíaRESUMEN
The balance of vascular tone between afferent (Af-) and efferent arterioles (Ef-Arts) is a crucial determinant of glomerular hemodynamics. Thus, to understand renal physiology and pathophysiology it is important to study the mechanisms that control their vascular resistance. In order to directly study these mechanisms, we have developed several in vitro microperfusion preparations of these arterioles, which have the advantage of allowing us to observe the arteriolar diameter directly in the absence of systemic hemodynamic and hormonal influences. Using these preparations, we have found that angiotensin II (Ang II) causes much stronger constriction in Ef- than in Af-Arts and that this difference is mediated by nitric oxide (NO)- and prostaglandin (PG)-induced modulation of Ang II action in the Af-Art. We have also found that the vasoconstrictor effect of Ang II on Ef-Arts is modulated by PG produced by the upstream glomerulus. Thus, this may be a mechanism whereby the glomerulus controls its own capillary pressure by releasing PG and thereby adjusting the resistance of the downstream Ef-Art. In addition, we have found that in these arterioles activation of the Ang II type 2 (AT2) receptor causes endothelium-dependent vasodilation, which modulates the vasoconstrictor action mediated by its type 1 (AT1) receptors. Such modulator mechanisms that regulate Af- and Ef-Art tone may play an important role in the precise control of glomerular hemodynamics, and their alterations may play a role in the pathophysiology of renal diseases, including hypertension. Indeed, we have demonstrated that the vasoconstrictor action of Ang II on the Af-Art is exaggerated in spontaneously hypertensive rats, an animal model of human essential hypertension, due to an impaired function of the AT2 receptor before the development of hypertension. Because such exaggerated vasoconstriction leads to the elevation of renal vascular resistance (an important pathogenic factor for essential hypertension), our findings suggest that impaired function of the AT2 receptor in Af-Arts may play a role in the pathophysiology of essential hypertension.
Asunto(s)
Angiotensina II/fisiología , Glomérulos Renales/irrigación sanguínea , Circulación Renal/fisiología , Vasodilatación/fisiología , Animales , HumanosAsunto(s)
Factor Natriurético Atrial/metabolismo , Nefropatías Diabéticas/fisiopatología , Circulación Renal/fisiología , Resistencia Vascular/fisiología , Nefropatías Diabéticas/etiología , Femenino , Tasa de Filtración Glomerular , Humanos , Glomérulos Renales/fisiopatología , Túbulos Renales Distales/fisiología , Túbulos Renales Proximales/fisiología , Masculino , Pronóstico , Sistema Renina-Angiotensina , Factores de Riesgo , Sensibilidad y Especificidad , Índice de Severidad de la EnfermedadRESUMEN
Aldosterone (Aldo) accelerates hypertension, proteinuria, and glomerulosclerosis in animal models of malignant hypertension or chronic renal failure. Aldo may exert these deleterious renal effects by elevating renal vascular resistance and glomerular capillary pressure. To test this possibility, directly examined were the action of Aldo on the afferent (Af) and efferent (Ef) arterioles (Arts). Examined were the effect of Aldo added to both the bath and lumen on the intraluminal diameter (measured at the most responsive point) of rabbits. Aldo caused dose-dependent constriction in both arterioles with a higher sensitivity in Ef-Arts. Vasoconstrictor action of Aldo was not affected by a mineralocorticoid receptor antagonist spironolactone and was reproduced by membrane-impermeable albumin-conjugated Aldo, suggesting that the vasoconstrictor actions are nongenomic. Pretreatment with neomycin (a specific inhibitor of phospholipase C) abolished the vasoconstrictor action of Aldo in both arterioles. In addition, the vasoconstrictor action of Aldo on Af-Arts was inhibited by both nifedipine and efonidipine, whereas that on Ef-Arts was inhibited by efonidipine but not nifedipine. The results demonstrate that Aldo causes nongenomic vasoconstriction by activating phospholipase C with a subsequent calcium mobilization thorough L- or T-type voltage-dependent calcium channels in Af- or Ef-Arts, respectively. These vasoconstrictor actions on the glomerular microcirculation may play an important role in the pathophysiology and progression of renal diseases by elevating renal vascular resistance and glomerular capillary pressure.
Asunto(s)
Aldosterona/farmacología , Aldosterona/fisiología , Glomérulos Renales/irrigación sanguínea , Resistencia Vascular/efectos de los fármacos , Vasoconstricción/efectos de los fármacos , Animales , Arteriolas/efectos de los fármacos , Arteriolas/fisiopatología , Bloqueadores de los Canales de Calcio/farmacología , Capilares/efectos de los fármacos , Capilares/fisiopatología , Cicloheximida/farmacología , Dactinomicina/farmacología , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/fisiopatología , Técnicas In Vitro , Glomérulos Renales/fisiopatología , Masculino , Antagonistas de Receptores de Mineralocorticoides/farmacología , Neomicina/farmacología , Inhibidores de la Síntesis de la Proteína/farmacología , Conejos , Espironolactona/farmacología , Resistencia Vascular/fisiología , Vasoconstricción/fisiologíaRESUMEN
Recent studies have demonstrated that thiazolidinediones, novel antidiabetic compounds that improve the insulin sensitivity, lower BP and decrease urinary protein excretion. However, neither the target vasculature nor the underlying mechanism for their actions is well understood. In this study, the action of troglitazone (Tro), a thiazolidinedione compound, on the glomerular afferent (Af-Arts) and efferent (Ef-Arts) arterioles, crucial vascular segments to the control of glomerular hemodynamics, were directly examined. Rabbit Af-Arts or Ef-Arts were microdissected from the superficial cortex and perfused at constant pressure. Increasing doses of Tro (10(-8) to 10(-5) M) were added to both the bath and lumen of preconstricted arterioles. In Af-Arts, Tro caused dose-dependent and biphasic dilation. Tro at 10(-5) M increased the diameter by 28 +/- 6% (n = 8, P < 0.01) until 20 min, with the diameter remaining at this level for 60 min, and then Tro began to dilate Af-Arts again. At 120 min, Tro at 10(-5) M further increased the diameter by 23 +/- 4% (n = 6). Disrupting the endothelium had no effect on either dilation (n = 7 or n = 5). Pretreatment with SKF 96365 (50 microM), which inhibits both voltage- and receptor-operated calcium channels, abolished the early-phase dilation without affecting the late-phase dilation; 20 or 120 min after adding Tro at 10(-5) M, the diameter increased by 4 +/- 2% (n = 7) or 28 +/- 3% (n = 6), respectively. In contrast to Af-Arts, Tro caused monophasic dilation in Ef-Arts; Tro at 10(-5) M did not cause significant dilation until 80 min, and at 120 min the diameter increased by 37 +/- 4% (n = 5). These results suggest that in the Af-Art Tro has biphasic endothelium-independent vasodilator action, which is partly mediated by an inhibition of calcium influx. This vasodilator action may play a role in the BP-lowering effect of Tro. In addition, by dilating the postglomerular Ef-Art, Tro may decrease the glomerular capillary pressure and hence the excretion of urinary protein.
Asunto(s)
Cromanos/farmacología , Circulación Renal/efectos de los fármacos , Tiazoles/farmacología , Tiazolidinedionas , Vasodilatadores/farmacología , Angiotensina II/farmacología , Animales , Arteriolas/efectos de los fármacos , Bloqueadores de los Canales de Calcio/farmacología , Cromanos/administración & dosificación , Relación Dosis-Respuesta a Droga , Endotelio Vascular/fisiología , Imidazoles/farmacología , Técnicas In Vitro , Masculino , Microcirculación/efectos de los fármacos , Conejos , Tiazoles/administración & dosificación , Factores de Tiempo , Troglitazona , Vasoconstrictores/farmacología , Vasodilatación/efectos de los fármacos , Vasodilatadores/administración & dosificaciónRESUMEN
BACKGROUND: The macula densa (MD), a plaque of specialized tubular epithelial cells, senses changes in tubular NaCl concentration and sends a signal(s) that controls the resistance of the glomerular afferent arteriole (Af-Art). This mechanism, called tubuloglomerular feedback (TGF), is thought to be important in the homeostasis of body fluids and electrolytes. Our aim was to determine the range of NaCl concentrations in tubular fluid at the MD that would elicit the Af-Art response. In addition, we examined the possible involvement of adenosine in transmitting the signal from the MD to the Af-Art. METHODS: Rabbit Af-Arts and attached MD were simultaneously microperfused in vitro, keeping pressure in the Af-Art at 60 mm Hg. RESULTS: Increasing the Na+/Cl- concentration of the MD perfusate from 26/7 to 41/22 mEq/L decreased the luminal diameter of the terminal Af-Art segment by 10 +/- 4% (N=9; P < 0.01). The response was maximal at 55/36 mEq/L (18 +/- 6%), so that further elevation of NaCl concentration had no additional effect (20 +/- 6% at 84/65 mEq/L). When FK838 (10(-6) mol/L), a specific adenosine A1 receptor antagonist, was added to both Af-Art perfusate and bath, Af-Art constriction was completely abolished. The maximum response was 20 +/- 3% before FK838 and 0.6 +/- 1% afterward (N=12). Adding adenosine at 10(-8) mol/L to both bath and perfusate significantly augmented Af-Art constriction induced by increased NaCl at the MD (P < 0.01); however, adding 10-8 to 10-6 mol/L adenosine to the MD perfusate had no effect regardless of the NaCl concentration at the MD. CONCLUSIONS: These results demonstrate that MD control of Af-Art resistance is induced by relatively low NaCl concentrations at the MD, and that activation of the adenosine A1 receptor in the vascular and interstitial space (but not the tubular lumen) may be essential for signal transmission from the MD to the Af-Art.