Effect of cyclosporin A on renal function and kidney growth in the uninephrectomized rat

This study was designed to characterize the effect of cyclosporin A (CsA) on renal function and compensatory kidney growth in a rat model of uninephrectomy (Ux). The infusion of CsA (12.5 mg/k body wt) after acute Ux resulted in a fall in glomerular filtration rate (GFR) and renal plasma flow (RPF) and a marked increase in renal vascular resistance (RVR). Three weeks following Ux, GFR was also reduced in CsA treated animals as compared to pair-fed controls (0.39 +/- 0.03 vs. 0.67 +/- 0.06 ml/min/100 g, P less than 0.001), but RPF was not (1.97 +/- 0.14 vs 2.19 +/- 0.34 ml/min/100 g). The reduction in GFR seen in rats treated with CsA was fully reversible two weeks after discontinuation of the drug. Three weeks after Ux, kidney weight in CsA-treated animals increased to the level of pair-fed controls (1.50 +/- 0.05 vs. 1.57 +/- 0.06 g) but renal cortical RNA (39.4 +/- 4.3 vs. 49.3 +/- 1.3 micrograms/ml, P less than 0.05), DNA (26.4 +/- 1.7 vs. 34.7 +/- 2.1 micrograms/ml, P less than 0.01), and protein content (6.4 +/- 0.3 vs. 7.8 +/- 0.2 mg/dl, P less than 0.001) were all markedly reduced. Unilateral renal denervation in CsA-treated rats resulted in an increase in GFR and RPF as compared to that of pair-fed sham-denervated animals also treated with CsA (0.57 +/- 0.06 vs. 0.39 +/- 0.03 ml/min/100 g, P less than 0.025 and 2.14 +/- 0.14 vs. 1.63 +/- 0.20 ml/min/100 g, P less than 0.025, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Absence of acute nephrotoxicity with low doses of cyclosporin: experimental study in the rat

No study has, to our knowledge, evaluated the acute effects of low immunosuppressive doses of cyclosporin (CsA) on renal function. To establish whether a relationship exists between the dosage of CsA and the onset of nephrotoxicity, 28 rats were studied by renal clearances before (control) and after i.v. administration of different doses of CsA: 3 mg/kg b.w. (group 1); 7 mg/kg b.w. (group 2); 11 mg/kg b.w. (group 3); 15 mg/kg b.w. (group 4). No change in renal function was observed between control and the post-CsA period in groups 1 and 2. GFR (inulin clearance) was decreased vs the control period in group 3 and group 4 (-22% and -37%, respectively, P less than 0.001); the difference between these two groups was statistically significant (P less than 0.01). Effective renal plasma flow (PAH clearance) was similarly decreased in groups 3 and 4 vs their control periods (-21% and -28%, respectively, P less than 0.001) due to the increase of total renal vascular resistance (+41% and +42%, respectively, P less than 0.001). Filtration fraction was significantly decreased by CsA in group 4 (P less than 0.01 vs the control period). PAH renal extraction, urinary volume, and sodium and potassium excretion were similar in all groups before and after CsA. PRA and ADH were significantly increased only in group 4 (P less than 0.01) vs the baseline values. A high and significant relationship was detected between CsA dosage and the decrease of GFR (r = 0.81, P less than 0.001) and RPF (r = 0.612, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of high-dose nifedipine on renal hemodynamics of cyclosporine-treated renal allograft recipients.

Cyclosporine has been shown to reduce renal perfusion and to decrease glomerular filtration rate. Experimental studies suggest that nifedipine might reverse this renal vasoconstrictive effect of cyclosporine. We studied renal hemodynamics of 5 cyclosporine-treated renal transplant recipients before and after 2 weeks of therapy with high-dose nifedipine (up to 120 mg/day). Pretreatment GFR and renal plasma flow (RPF) were decreased. Following administration of nifedipine, RPF increased by 18% (P less than 0.01), while GFR did not change. Filtration fraction decreased by 10.5% (P less than 0.01). Mean arterial pressure declined from 111 +/- 5 to 96 +/- 3 mmHg (P less than 0.01). Renal vascular resistance dropped by 25% (P less than 0.01). Calculated postglomerular plasma flow increased by 20.5% (P less than 0.01). Urinary albumin excretion rate was unaffected. Cyclosporine whole blood levels were unchanged. The increase in RPF and in postglomerular plasma flow suggests that high-dose nifedipine might lessen cyclosporine-induced glomerular and interstitial ischemia in renal allograft recipients.     

Co-participation of thromboxane A2 and leukotriene C4 and D4 in mediating cyclosporine-induced acute renal failure.

The relative role of thromboxane (TxA2) and sulfidopeptide leukotrienes C4 (LTC4) and D4 (LTD4) in the acute renal failure induced by cyclosporine was studied in the rats. Bolus i.v. administration of 20 mg/kg of CsA but not vehicle to adult male Sprague-Dawley rats resulted in a significant fall in glomerular filtration rate from 0.85 +/- 0.10 and renal plasma flow (RPF) 2.45 +/- 0.14 ml/min/100 g body wt to values at 20 min of 0.47 +/- 0.03 and 1.01 +/- 0.12 ml/min/100 g body wt (P less than 0.01), respectively, without a fall in mean arterial pressure. This hemodynamic effect was maintained for the following 40-min period. Pretreatment of rats with the TxA2 receptor antagonist GR32191 (3 mg/kg i.v.) allowed a partial but significant preservation of GFR (0.60 +/- 0.05 ml/min/100 g body wt) and RPF (1.55 +/- 0.12 ml/min/100 g body wt). In addition, the antagonism of endogenously produced LTC4 and LTD4 with the putative receptor antagonist L-649,923 (1 mg/kg i.v.) partially prevented the fall in GFR (0.65 +/- 0.07 ml/min/100 g body wt) and RPF (1.80 +/- 0.18 ml/min/100 g body wt) at 20 min after CsA injection. The combined administration of GR32191 and L-649,923 completely abolished the CsA-induced decline in GFR (0.80 +/- 0.09 ml/min/100 g body wt) and RPF (2.40 +/- 0.12 ml/min/100 g body wt). These findings suggest that TxA2 and LTC4/LTD4 participate in mediating renal function deterioration induced by acute CsA administration in the rat.     

Effects of a two-month treatment with low oral doses of cyclosporin on renal function

To test the effects of short-term therapy with low doses (LD) of cyclosporin A (CsA) in subjects with normal renal function, seven patients receiving CsA to treat psoriasis were studied. Clearances in maximal H2O diuresis were performed to evaluate changes in GFR (CIn), RPF (CPAH) and tubular function before starting CsA (BAS), after 2 days (S1) and 1 month (S2) of oral therapy with 5 mg/kg per day CsA. The study was repeated at the withdrawal of CsA after tapering (S3) and 2 months after the withdrawal (S4). The studies were performed 12 h after the evening dose of CsA. RPF was significantly less than in BAS throughout the therapy and returned almost to basal values in S4. GFR was significantly less than in BAS both in S2 and in S3. In S4, in spite of an increase, GFR was still significantly less than in BAS. Both in S2 and in S3 proximal tubular fractional sodium reabsorption was significantly less than in BAS and, consequently, both sodium delivery to diluting segments and sodium reabsorption in diluting segments increased. Moreover, both in S2 and in S3 fractional sodium reabsorption in diluting segments and free-water generation were greater than in BAS. In S4 tubular function returned almost to basal values. Our data suggest that short-term therapy with low dose CsA impairs renal function; this impairment is not completely reversed after drug withdrawal.     

Renal kallikrein responses to dietary protein: a possible mediator of hyperfiltration

We studied GFR, RPF and renal kallikrein in rats fed 9%, 25%, or 50% protein (casein) diets for 8 to 13 days. CFR and RPF increased progressively with increasing dietary protein. Renal excretion of active kallikrein (microgram/day) was 128 +/- 9, 174 +/- 11 and 228 +/- 14 in 9%, 25%, and 50% protein-fed rats, respectively (P less than 0.02 or less between groups). Prokallikrein excretion in these groups was 23 +/- 7, 77 +/- 11 and 118 +/- 15 micrograms/day, respectively (P less than 0.005 or less between groups). The in vivo renal kallikrein synthesis rate, relative to total protein synthesis, was reduced in 9% protein-fed rats (2.74 +/- 0.24) compared to rats fed 25% (3.93 +/- 0.34, P less than 0.02) or 50% protein (4.41 +/- 0.30, P less than 0.001). These changes in synthesis and excretion rates were not accompanied by changes in renal tissue levels of active or prokallikrein. In all groups, GFR and RPF correlated directly with the renal excretion of active kallikrein, prokallikrein or total kallikrein (r = 0.41 to 0.66, P less than 0.01). Treatment of 50% protein-fed rats with aprotinin, a kallikrein inhibitor, markedly lowered renal and urinary kallikrein-like esterase activity. Left kidney GFR and RPF were significantly reduced in aprotinin-treated rats compared to vehicle-treated rats (1.54 +/- 0.15 and 4.86 +/- 0.38 ml/min vs. 1.89 +/- 0.10 and 5.93 +/- 0.22 ml/min, GFR and RPF, respectively, P less than 0.05 or less).(ABSTRACT TRUNCATED AT 250 WORDS)     

No involvement of antidiuretic hormone in acute antidiuresis during PEEP ventilation in humans

Decreased urinary output (Vu ml/min) after institution of PEEP is attributed to a variety of mechanisms including decreased cardiac output and renal blood flow (RBF), activation of neurohormonal reflexes, increased catecholamines, plasma renin activity (PRA), and antidiuretic hormone (ADH) release. To evaluate these factors, seven normovolemic patients (36 yr +/- 13 SD), free of preexisting lung, cardiac, or renal disease, requiring continuous mandatory ventilation for neurologic reasons were studied. The authors measured or calculated: total blood volume (TBV) (51Cr); right atrial, pulmonary arterial, pulmonary wedge, and systemic pressures, cardiac index (CI); renal plasma flow (RPF) (iodohippurate sodium 131I [131I PAH] clearance); glomerular filtration rate (GFR) (creatinine clearance), free water clearance (CH2O), osmolal clearance (Cosm), fractional excretion of sodium (FENa+) and potassium (FEK+); and plasma renin activity (PRA) (ng X ml-1 X h-1), plasma ADH (pg/ml; radioimmunoassay), epinephrine (E in pg/ml), and norepinephrine (NE in pg/ml) (double-isotope radioenzymatic assay). Two conditions were studied after 90-min steady state: 1) zero PEEP (ZEEP); and 2) 15 cmH2O PEEP. PEEP caused a significant decrease in CI (-21%; P less than 0.01) and RPF (-19%; P less than 0.05) without significant decrease in GFR. A significant decrease in Vu (-55%; P less than 0.05), FENa+ (-39%; P less than 0.05) and Cosm (-36%; P less than 0.25) occurred without modification in CH2O. Plasma ADH remained in the normal range and did not increase when PEEP was applied.(ABSTRACT TRUNCATED AT 250 WORDS)     

Renal hemodynamics and urinary excretion of 6-keto-prostaglandin F1 alpha and thromboxane B2 in newly diagnosed type I diabetic patients

We have studied the functional importance of renal eicosanoids in renal hemodynamics of seven newly diagnosed insulin-dependent diabetes mellitus (IDDM) patients by treatment with two structurally unrelated inhibitors of cyclooxygenase (i.e., piroxicam and sulindac). Glomerular filtration rate (GFR), renal plasma flow (RPF), daily urinary excretion of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha, the stable hydrolysis product of prostacyclin), and thromboxane B2 (TXB2, the stable hydrolysis product of thromboxane A2) were measured before, during, and after piroxicam (all patients) or sulindac (3 patients) treatment. Urinary excretion of 6-keto-PGF1 alpha was significantly increased (P less than .01) in diabetic patients compared with seven healthy subjects, whereas urinary excretion of TXB2 was unchanged. The baseline value of GFR was significantly (P less than .01) higher in diabetic compared with normal volunteers, whereas baseline RPF was comparable in both groups. Piroxicam (20 mg/day) reduced urinary excretion of 6-keto-PGF1 alpha and TXB2 by 65.7 +/- 26 and 64.6 +/- 33%, respectively. These biochemical changes were temporally associated with the approximately 19% decrease in GFR (P less than .01). A week after discontinuation of the drug, GFR and urinary excretion of 6-keto-PGF1 alpha were still significantly (P less than .05) reduced, whereas urinary excretion of TXB2 returned to control values. In contrast, urinary excretion of eicosanoids and renal function were not affected by sulindac (0.4 g/day) treatment. No functional changes were detected in healthy subjects despite a similar suppression of renal cyclooxygenase activity when they were treated with piroxicam.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of acute and chronic dosing of NSAIDs in patients with renal insufficiency

Administration of nonsteroidal anti-inflammatory drugs (NSAIDs) to patients with chronically impaired renal function has been reported to cause abrupt and sustained reductions in renal plasma flow (RPF), glomerular filtration rate (GFR), and solute and water excretion in association with decreased renal prostanoid production. However, the time course of these acute effects and whether they are sustained during chronic exposure to the NSAIDs are unknown. Accordingly, using standard clearance and balance techniques, we investigated the effects of acute (zero to four hours) and chronic (five days) oral administration of two different NSAIDs on renal function in patients with stable, mild to moderate chronic renal insufficiency (CRI) and in normal subjects. In patients, acute oral administration of ketoprofen (K) and indomethacin (I) resulted in significant decreases in GFR (K: from 36 +/- 3 to 20 +/- 4 ml/min, P = 0.001; I: from 37 +/- 6 to 30 +/- 7 ml/min, P = 0.032; in RPF (K: from 194 +/- 21 to 146 +/- 21 ml/min, P = 0.002; I: from 222 +/- 33 to 147 +/- 18 ml/min, P = 0.016); and in urinary PGE2 excretion (K: from 0.60 +/- 0.25 to 0.08 +/- 0.02 ng/min, P = 0.05; I: from 0.34 +/- 0.06 to 0.18 +/- 0.06 ng/min, P = 0.042). Fractional excretion of sodium chloride and fractional free water clearance (CH2O/CIn) also decreased significantly after both agents. In normal subjects, GFR and RPF were not significantly decreased after acute dosing, whereas urinary PGE2 and fractional excretions of NaCl and free water decreased significantly.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of nonsteroidal antiinflammatory drugs on renal function in sickle cell anemia

Renal hemodynamics and solute and water handling were evaluated in 19 sickle cell patients and 8 matched normal subjects during water diuresis, before and after acute oral administration of a nonsteroidal antiinflammatory drug (NSAID). Baseline GFR and RPF were higher in the patients compared to the normals. In contrast to normals, indomethacin and sulindac induced a 16% and 14% decrease in GFR, respectively. Indomethacin resulted in a slight increase in UOsm in normals, but a substantially greater rise in the patients. Following indomethacin a greater fall in FENa, fractional solute delivery to the diluting segment of the nephron [(CH2O + CNa + K)/GFR], fractional solute reabsorption in the diluting segment [CH2O/GFR] and the fraction of distally delivered solute reabsorbed [CH2O/(CH2O + CNa + K)] was observed in the sickle cell patients than in the normal subjects. A similar trend, but of significantly lesser magnitude than that induced by indomethacin, was observed following sulindac in the sickle cell patient. The data imply that the supranormal GFR observed in the sickle cell patients was prostaglandin-mediated. The effects of NSAID's on renal solute and water handling in the sickle cell patients are compatible with a prostaglandin-dependent decreased salt reabsorption in the medullary thick ascending limb of Henle, together with a hyperfunctioning proximal tubule. The data also imply an additional indomethacin-sensitive antinatriuretic effect in the diluting segment in these patients. Moreover, the results suggest that in sickle cell anemia sulindac may not have a "renal sparing" advantage over other NSAID's.     

Effect of felodipine on renal haemodynamics and tubular sodium handling in cyclosporin-treated renal transplant recipients.

The effect of a single oral dose of 10 mg of the calcium antagonist felodipine or placebo was investigated in 10 cyclosporin-treated renal transplant recipients before, during, and after an acute intravenous infusion of cyclosporin in a randomised, single-blind cross-over study. Renal plasma flow (RPF), glomerular filtration rate (GFR), renal tubular sodium and water handling as judged by the lithium clearance technique, and plasma concentrations of angiotensin II (AngII), aldosterone (Aldo), atrial natriuretic factor (ANF), and arginine vasopressin (AVP) were measured. Both RPF and GFR increased after felodipine (mean increase: RPF, 38.7%; GFR, 16.2%; P less than 0.01 for both) in spite of a significant decrease in both systolic and diastolic blood pressure (mean decrease 10.6% and 16.0% respectively, P less than 0.02 for both). Estimated by the lithium clearance technique felodipine induced a decrease in fractional reabsorption in the proximal tubules (mean 72.0% vs 63.0%, P less than 0.01), an increase in proximal output of fluid (mean 11.0 ml/min vs 16.0 ml/min, P less than 0.01), and a decrease in distal fractional reabsorption of sodium (mean 90.5% vs 83.9%, P less than 0.05) resulting in a significant natriuresis and diuresis. Ang II, Aldo, ANF, or AVP did not change. Intravenous infusion of cyclosporin per se did not influence any of the parameters. It is concluded that a single dose of felodipine in cyclosporin treated renal transplant recipients has beneficial effects on blood pressure, renal haemodynamics, and renal tubular sodium and water handling, which seems to compensate for some of the adverse effects of cyclosporin. It is suggested that these effects result from a direct vasodilatation and an effect on proximal tubular function.     

Endothelin receptor antagonism is protective in in vivo acute cyclosporine toxicity.

Endothelin (Et) has been implicated in cyclosporine A (CsA) nephrotoxicity. We have previously shown that CsA treatment in rats results in up-regulation of Et receptors specifically within the kidney. The role of Et in vivo CsA nephrotoxicity was therefore studied further with a new competitive antagonist, BQ-123, specific for Et(A) receptors (EtRA). Systemic administration of CsA in Munich-Wistar rats resulted in marked glomerular hypoperfusion and hypofiltration, with RPF in left and right kidneys falling by some 40% to 1.60 +/- 0.25 and 1.73 +/- 0.38 ml/min and GFR decreasing by some 20% to 0.61 +/- 0.05 and 0.67 +/- 0.11 ml/min, respectively. Selective infusion of EtRA into the left renal artery following systemic CsA treatment had no effect on this hemodynamic pattern (RPF 1.58 +/- 0.29 and 1.92 +/- 0.34 ml/min and GFR 0.60 +/- 0.09 and 0.70 +/- 0.08 ml/min in left and right kidneys, respectively, P = NS vs. CsA period). By contrast, intrarenal infusion of EtRA prior to systemic administration of CsA resulted in a strikingly different pattern of renal hemodynamics. Thus, EtRA pretreatment in the left kidney protected against glomerular dysfunction following CsA: RPF was maintained, 3.23 +/- 0.28 ml/min versus 2.96 +/- 0.31 (P = NS EtRA vs. EtRA + CsA), as was the GFR, 1.04 +/- 0.16 ml/min versus 1.12 +/- 0.09 (P = NS). However, the contralateral right kidneys of these rats, not pretreated with EtRA, showed no protective effect: RPF decreased from 3.15 +/- 0.34 ml/min to 2.39 +/- 0.19 and GFR from 1.04 +/- 0.10 ml/min to 0.85 +/- 0.07 (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Renal hemodynamics and pharmacokinetics of bosentan with and without cyclosporine A

Renal hemodynamics and pharmacokinetics of bosentan with and without cyclosporine A. BACKGROUND: Endothelins may play an important role in cyclosporine A (CsA)-induced renal vasoconstriction. Therefore, the effects of a mixed endothelin A and B receptor antagonist, bosentan (BO), on CsA were studied. METHODS: BO was given either alone or combined with CsA to healthy subjects in a double-blind, placebo-controlled, cross-over study. Standardized renal hemodynamics took place after a single dose of BO or placebo and after seven days of regular intake of CsA + BO or CsA + placebo. CsA was administered as a dose-adjusted regimen to achieve predetermined target trough levels. A pharmacokinetic study of CsA and BO was performed. RESULTS: A single dose of BO did not affect renal hemodynamics. After seven days of coadministration with CsA, BO significantly attenuated both the overall CsA-induced fall of renal plasma flow (RPF; placebo, 594 +/- 85; CsA + placebo, 490 +/- 93; CsA + BO, 570 +/- 106* mL/min, *P < 0.01) and the maximal RPF fall (P < 0.01) observed five hours after CsA intake. The CsA-induced rise of blood pressure and the decrease of glomerular filtration rate (GFR) were not influenced by comedication with BO. After seven days of CsA + BO, the area under the curve (AUC) of BO was nearly doubled compared with the AUC after a single dose of BO (P < 0.05). To reach the CsA target trough levels after seven days, the average CsA dose was increased by 35% when given with BO, as compared with placebo (P = 0.01). CsA exposure (trough levels, AUC) was not statistically different after CsA + placebo and after CsA + BO. CONCLUSIONS: Assuming CsA nephrotoxicity is mainly due to vasoconstriction, BO has the potential to attenuate the CsA renal toxicity by markedly blunting the renal hypoperfusion effect of CsA. A complex drug interaction between BO and CsA was observed.     

Prevention of acute cyclosporine nephrotoxicity by atrial natriuretic factor after ischemia in the rat

The present experimental study investigates whether the atrial natriuretic factor (ANF) is able to prevent the nephrotoxic effects of cyclosporine infused after 30 min of warm renal ischemia in the rat. At 2 hr after the end of ischemia, the glomerular filtration rate was improved by an ANF infusion: 390 +/- 19 microliters/min/100 g versus 298.3 +/- 31 microliters/min/100 g in ANF and saline-infused rats, respectively (P less than 0.05). Intravenous CsA infusion at a dose of 2.5 mg/kg/day produced a more pronounced fall in GFR when compared with the control: 205.4 +/- 19.7 microliters/min/100 g versus 298.3 +/- 31 microliters/min/100 g in CsA and saline, respectively (P less than 0.05). In contrast, a synthetic rat atriopeptin III (0.5 microgram/kg/min) infusion after ischemia given together with CsA prevented its deleterious effects upon GFR: 316 +/- 22 microliters/min/100 g versus 205.4 +/- 19 microliters/min/100 g in ANF/CsA versus CsA alone (P less than 0.001). Moreover, the natriuretic ANF effects remained unaffected by high plasma CsA peak levels: indeed, other parameters of renal function--urinary flow, urinary sodium concentration and excretion rates, and urinary sodium reabsorption and fractional excretion rates, were significantly increased in ANF alone or CsA/ANF groups. These preliminary results suggest that ANF may be useful in renal transplantation or in the management of patients given large doses of CsA (liver or heart transplant) since, despite nephrotoxic CsA levels (greater than 1500 ng/ml), ANF provides an improved GFR and tubular function after ischemia.     

Cyclosporine-induced renal dysfunction in human renal allograft recipients

Cyclosporine-treated renal allograft recipients frequently suffer CsA-related nephrotoxicity and hypertension. This study demonstrates that glomerular filtration rate is reduced acutely by 13% (P less than 0.02) and renal vascular resistance increased by 30% (P less than 0.05), immediately after patients take their CsA dose. The reduction in GFR is directly related to their trough CsA level (r = 0.82; P less than 0.01). The lower the trough CsA level the greater the fall in GFR after the CsA dose. Plasma renin activity does not increase after the CsA dose (pre-CsA 0.6 +/- 0.2 ng/L/sec vs. post-CsA 0.4 +/- 0.1 ng/L/sec; P = NS), and therefore cannot be responsible for the reduction in renal function. Short-term nifedipine treatment is effective in preventing the acute reduction in GFR (P less than 0.05). This occurred despite no apparent effect of nifedipine in altering trough or post-dose CsA levels. Furthermore nifedipine was effective in lowering both the mean arterial blood pressure (109 mmHg to 94 mmHg; P less than 0.01) and the elevated renal vascular resistance (25% reduction; P less than 0.02) observed in these patients. These results suggest that nifedipine may be a suitable agent for limiting acute CsA nephrotoxicity and for treating CsA-associated hypertension in renal allograft recipients.     

Effect of 6 weeks of vitamin E administration on renal haemodynamic alterations following a single dose of neoral in healthy volunteers.

BACKGROUND: A single oral dose of cyclosporin-A (CsA) transiently reduces renal plasma flow (RPF) and glomerular filtration rate (GFR) in transplant patients and, in some patients, chronic administration of CsA leads to renal impairment and fibrosis. Based on experimental studies, several mediators including free radicals have been proposed to account for CsA-nephrotoxicity. We have previously reported that administration of the antioxidant vitamin E in a rat model of chronic CsA-nephrotoxicity reduces renal fibrosis and maintains renal function. METHODS: In the present study, the effect on renal haemodynamics of a single dose of the new oral formulation of CsA (neoral) was assessed before and after 6 weeks of vitamin E (800 IU/day, 2-fold increase in serum vitamin E). GFR (inulin clearance) and RPF (para-amino hippuric acid clearance) were measured before and after a single dose of 5 mg/kg of neoral in 12 healthy subjects under standardised conditions. RESULTS: Although the mean area under the curve of the CsA levels was 21% lower after the vitamin E period, the peak CsA level at 120 min after neoral was similar both before and after vitamin E administration. At 120 min after neoral, a transient reduction in RPF and GFR was noted both before and after vitamin E administration. The nadir of the reductions in RPF (-81 +/-27 ml/min) and GFR (-14 +/- 6 ml/min) at 120 min compared with baseline tended to be lower before than after the treatment with vitamin E (-51 +/- 33 ml/min of RPF and -12 +/- 8, ml/min of GFR, respectively). Plasma and urine levels of F2-isoprostanes (free radical-catalysed vasoconstrictive prostanoids (F2-iso) at 120 min after the administration of neoral were not different from the pre-neoral levels. CONCLUSION: The findings demonstrate that a single oral dose of neoral causes transient, yet significant, reductions in RPF and GFR, and suggest that F2-iso might not be involved in the CsA-induced acute renal vasoconstriction. The tendency for a lower reduction in RPF and GFR following CsA during the vitamin E period in healthy humans warrants additional studies in transplant patients.     

Tubular handling of amino acids after intravenous infusion of amino acids in healthy humans.

To examine the fractional excretion of amino acids after an increase in the filtered load, and to study a possible coupling between proximal tubular reabsorption of individual amino acids and sodium/water, eleven healthy subjects were examined before and during intravenous infusion of a mixture of essential and non-essential amino acids. Thirteen healthy subjects, who received isotonic glucose instead, participated in an identical time-control study. Glomerular filtration rate (GFR), renal plasma flow (RPF), and proximal and distal absolute and fractional tubular reabsorption of sodium and water (PARNa, PFRNa/water, DARNa, and DFRNa) evaluated by the lithium clearance method were determined during four clearance periods of 30 min each. After amino acid infusion, GFR and RPF increased, whereas filtration fraction (FF) was unchanged. PARNa was unchanged, but lithium clearance increased significantly (P less than 0.05) and PFRNa/water fell, indicating an increased delivery of sodium and water out of the proximal tubules. DARNa increased, but DFRNa was unchanged, thus no net increase was recorded in urinary sodium and water output. In the time-control study, no changes in kidney function were seen. Absolute excretion of amino acids increased for glutamic acid, serine, glutamine, glycine, threonine, histidine, alanine, arginine, tyrosine, valine, methionine, isoleucine, phenylalanine, leucine, and lysine (P less than 0.01), and fractional excretion increased for all but glutamic acid, tyrosine, arginine, isoleucine, and leucine. Reabsorption of amino acids was enhanced uniformly and almost paralleled the filtered load without any sign of saturation of the reabsorption mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of felodipine on renal function and blood pressure in cyclosporin-treated renal transplant recipients during the first three months after transplantation

Background: Due to their vasodilatory effect, calcium antagonist may have a renoprotective against cyclosporin (CsA)-induced nephrotoxicity and rise in blood pressure (BP) seen in renal transplantation. Methods: In order to evaluate the effect of the calcium antagonist felodipine on renal function and BP during cyclosporin treatment, 79 CsA-treated renal transplant recipients were investigated during the first 3 months after transplantation in a randomized, double-blind, placebo-controlled study with two parallel groups. Felodipine (ER tablets, 10 mg) or placebo was given prior to transplantation and each day during the study period. The patients were assessed twice, i.e. at 4-6 weeks and at 10-12 weeks after transplantation. Renal plasma flow (RPF) and glomerular filtration rate (GFR) were measured by constant infusion technique. Tubular function was estimated from clearance of lithium. Results: At 6 weeks after transplantation, felodipine caused a significantly higher RPF [felodipine: 219±70 ml/min; placebo: 182±56 ml/min (mean±1 SD); P=003]. No differences were found in GFR, filtration fraction (FF), tubular sodium handling, or sodium excretion. Felodipine lowered BP significantly. At 12 weeks after transplantation, felodipine caused a significantly higher GFR (felodipine; 49±18 ml/min; placebo: 40±16 ml/min; P=0.05) and RPF (felodipine: 225±77 ml/min; placebo: 175±48 ml/min; P<0.01). No difference was found in FF. Felodipine lowered BP significantly. No differences were found with regard to duration of primary anuria, hospitalization time; number of rejection episodes, plasma creatinine day 7 post-transplant, or treatment doses of CsA. Conclusions: It is concluded that in renal transplant recipients treated with CsA, felodipine significantly increased both GFR and RPF 3 months after transplantation when compared with placebo, despite a concomitant lowering of BP. A possible antagonizing affect of felodipine against CsA-induced nephrotoxicity in these patients is suggested.     

Renal and metabolic effects of L-arginine infusion in kidney transplant recipients.

AIM AND METHODS: In order to investigate the role of kidney damage on renal response to L-arginine (L-Arg) infusion in transplant patients receiving cyclosporine A (CsA) treatment, we assessed systemic and glomerular hemodynamic variables, the fraction excretion of urinary sodium, albumin, cyclic GMP (as an index of nitric oxide (NO) production from L-Arg) and urea excretion (as an index of ureagenesis), and glucoregulatory hormone levels in five normal volunteers and 21 renal allograft recipients (aged 10-20 years) treated with CsA, 10 with normal renal function and 11 with chronic renal insufficiency. RESULTS: In the normal subjects, L-Arg infusion (290 mg/min/1.73 m2 for 1 h) significantly reduced mean arterial pressure (MAP) (76+/-7 to 70+/-5 mmHg) and renal vascular resistance (RVR), and increased GFR (103+/-9 to 122+/-7 min/1.73 m2), RPF, urinary cyclic GMP excretion (0.40+/-0.1 to 0.60+/-0.1 nmol/100 ml glomerular filtrate (GF)), and sodium and albumin excretion. Neither the patients with chronic graft dysfunction nor those with a normal graft responded to L-Arg infusion: RVR remained high, and MAP, GFR, RPF, fractional excretion of sodium and urinary excretion of albumin and cyclic GMP were unchanged in both groups of patients. Glucagon, insulin and urinary urea excretion rose significantly in controls and both patient groups. CONCLUSION: The hemodynamic effects of L-Arg infusion were inhibited in the patients, regardless of their degree of renal function, possibly because L-Arg-NO production was blunted.     

肾脂肪囊内注射黄芪和多巴胺对大鼠内毒素休克所致急性肾衰竭的防治作用

目的:探讨肾脂肪囊内联合应用黄芪和多巴胺对大鼠内毒素休克所致急性肾衰竭的防治作用及其机制.方法:SD大鼠随机分为对照组、内毒素组、静脉应用与肾脂肪囊内应用黄芪和多巴胺组,分别测定平均动脉压(MAp)、肾血浆流量(RPF)、肾小球滤过率(GFR)、尿量(UO)、滤过钠排泄分数(FENa)以及肾组织一氧化氮(NO)和内皮素(ET)浓度,光镜及电镜观察病理改变.结果:内毒素组MAp和RPF、GFR、UO显著降低,FENa初4 h极度减少,随后增高,至12 h后接近或大于2%,肾组织NO和ET浓度明显升高;黄芪和多巴胺联合应用可稳定MAp,提高RPF和GFR,增加UO,改善FENa,降低肾组织NO和ET水平,减轻组织病理损害,尤以肾脂肪囊内给药组肾脏保护效果显著,实验后期作用更为明显.结论:黄芪和多巴胺联合应用可纠正大鼠内毒素休克低血压状态,改善肾脏功能,减轻病理损害,可能与作用于NO和ET系统有关.