Animal studies have implicated an important role of nitric oxide (NO) in the regulation of blood pressure, renal hemodynamics, and renal excretion of sodium. NG-monomethyl-L-arginine (L-NMMA) is a specific, competitive inhibitor of NO synthesis interfering with NO synthase. The purpose of the present study was to investigate the effect of L-NMMA on renal plasma flow (RPF), glomerular filtration rate (GFR), urinary sodium excretion (UNa), fractional sodium excretion (FENa), fractional lithium excretion (FELi), mean arterial blood pressure (MAP), and heart rate (HR) in healthy humans. In a randomized placebo-controlled study, 23 healthy subjects were randomized to receive either bolus injection of L-NMMA (3 mg/kg in 10 ml saline, n = 12 subjects) or placebo (10 ml saline, n = 11). GFR and RPF were measured using the renal clearances of 51Cr-labeled EDTA and 125I-labeled hippuran by the constant infusion technique. L-NMMA treatment induced 60 min after injection a 14.6% decrease in RPF, a 5.8% decrease in GFR, a 9.8% increase in filtration fraction, a 34.7% decrease in UNa a 28.6% decrease in FENa, and a 12.1% decrease in FELi. These changes were still evident 120 min after injection. None of the effect parameters were changed after placebo, except FENa, which increased 9.9% 60 min after injection. Ten minutes after L-NMMA injection, MAP increased significantly (80 vs. 88 mmHg), and HR decreased (58 vs. 47 beats/min). The changes in HR and MAP normalized within 30 min. L-NMMA significantly reduced the plasma level of cGMP 60 min (3.0 vs. 3.7 pmol/l) and 120 min after injection (2.5 vs. 3.7 pmol/l). It is concluded that, in healthy humans, NO is a regulator of renal hemodynamics as a tonic vasodilator and a regulator of sodium excretion, due at least in part to a proximal tubular effect.

Animal studies have indicated that increased nitric oxide (NO) synthesis plays a significant role in the renal adaptation to increased sodium intake. To investigate the role of NO during increased sodium intake in humans, we studied the effect of acute, systemic injection of N G-monomethyl-l-arginine (l-NMMA) on renal hemodynamics [glomerular filtration rate and renal plasma flow (GFR and RPF, respectively)], urinary sodium excretion (FENa), systemic hemodynamics [mean arterial blood pressure and heart rate (MAP and HR)], and plasma levels of several vasoactive hormones in 12 healthy subjects during high (250 mmol/day) and low (77 mmol/day) sodium intake in a crossover design. The sodium diets were administered for 5 days before the l-NMMA treatments, in randomized order, with a washout period of 9 days between each diet and l-NMMA treatment. GFR and RPF were measured using the renal clearance of51Cr-labeled EDTA and125I-labeled hippuran by the constant infusion technique in clearance periods of 30-min duration. Two baseline periods were obtained, after whichl-NMMA was given (3 mg/kg over 10 min), and the effect of treatment was followed over the next five clearance periods. During high sodium intake,l-NMMA induced a more pronounced relative decrease in RPF ( P = 0.0417, ANOVA), a more pronounced relative decrease in FENa( P = 0.0032, ANOVA), and a more pronounced relative increase in MAP ( P= 0.0231, ANOVA). During low sodium intake, the effect ofl-NMMA on FENa was abolished. During low sodium intake, l-NMMA induced a sustained drop in plasma renin (31 ± 5 vs. 25 ± 5 μU/ml, P < 0.001), which was not seen during high sodium intake. The data indicate that increased production of NO is an important part of the adaptation to increased dietary sodium intake in healthy humans, with respect to renal hemodynamics, sodium excretion, and the secretion of renin.

Our purpose was to elucidate the hypothesis that paracrine-produced transforming growth factor (TGF)-beta1 regulates the accumulation of extracellular matrix (ECM) in renal glomeruli, a hallmark of diabetic nephropathy. To produce TGF-beta1 from the juxtaglomerular apparatus in mouse kidneys, we cloned a mouse Ren-1c promoter fragment (-4.100 to +6 base pairs) upstream of porcine TGF-beta1 (pTGF-beta1) cDNA, mutated to ensure secretion of biologically active TGF-beta beta1. The resulting transgenic mice had significantly more TGF-beta1 in their kidneys than was in those of nontransgenic controls, as confirmed by immunohistochemistry, and the production of TGF-beta1 was enhanced in vivo by captopril-induced stimulation of the Ren-1c promoter. Overproduction of pTGF-beta1 close to the glomerulus resulted in a local accumulation of ECM, composed partly of collagen type IV and laminin, and thickening of the basement membrane, characteristic features of diabetic nephropathy. Interstitial accumulation of ECM and signs of tubular atrophy were present only in older mice (>5 months of age). Results from in situ hybridization and immunohistochemistry suggest that pTGF-beta1 stimulated the production of endogenous TGF-beta1 along collecting ducts and connecting tubules. The increased amount of biologically active TGF-beta1, transgenic as well as endogenous, was corroborated by heightened proteoglycan synthesis from incubated kidney slices. This transgenic model demonstrates that sustained local expression of TGF-beta1 leads to glomerulopathy. We conclude that autocrine- or paracrine-produced TGF-beta1 may play a role in the development of glomerular diseases, such as diabetic nephropathy.

SUMMARY:Transforming growth factor-␤1 (TGF-␤1) may play a major role in the pathogenesis of glomerulopathy and end-stage renal disease (ESRD). The aim of this study was to explore the functional consequences of localized overproduction of TGF-␤1 in relation to glomerular ultrastructure and the composition of the extracellular matrix (ECM) in the inner medulla. We used a transgenic mouse with overexpression of TGF-␤1 targeted to the juxtaglomerular apparatus (JGA) by the Ren-1 c promoter. The kidney function was evaluated using urine production and metabolite excretion over a 24-hour period, glomerular filtration rate (GFR), and concentrating ability. The glomerular structure was analyzed in terms of volume, ie, the volume of the mesangium per glomerulus (Vv[mes/glom]) and the volume of the matrix per glomerulus (Vv[matrix/glom]), ECM per glomerulus, the area of the filtration surface, and the thickness of the peripheral basement membrane (PBM). Immunohistochemistry or in situ hybridization was used to examine the expression of aquaporin 2 (AQP2), plasminogen activator inhibitor-1 (PAI-1), and the composition of the ECM in the inner medulla. The mice exhibited polyuria, reduced concentrating ability, decreased GFR, and albuminuria paralleled by increased glomerular volume, with increased volume of ECM, decreased filtration surface, and thickening of the PBM being detectable between 1 and 2 months of age. The deposition of glomerular ECM was accompanied by increased levels of PAI-1. As estimated by excretion of Clara cell protein-1 (CC16) and lysozyme, tubular damage occurred only in older mice. Collagen Type I was deposited in the inner medulla in the presence of normal AQP2-expression in the collecting ducts. This study reached the following conclusions: (a) TGF-␤1 reduces the GFR and the glomerular filtration surface, (b) TGF-␤1 induces albuminuria in association with widening of the PBM, (c) expansion of the mesangial volume seems to precede the widening of the PBM, (d) TGF-␤1-induced accumulation of glomerular ECM is partly explained by increased PAI-1 expression, (e) Decreased concentrating ability and polyuria caused by accumulation of ECM in the inner medulla may be an early marker of glomerular diseases associated with increased expression of

in a group of patients with chronic glomerulonephritis and mildly to moderately impaired renal function, it was found by means of echocardiography that there was a higher LV mass index and decreased systolic function, when compared with healthy controls. In addition, the patients had diastolic dysfunction of primarily the left ventricle. The echocardiographic findings were not correlated to BP level or renal function. This suggests that factors other than GFR or BP per se might be involved in the pathogenesis of cardiac dysfunction, at an early stage.