The effect of rapamycin on kidney function in the Sprague-Dawley rat.

The effects of rapamycin (RAPA) on kidney function and histology were investigated in the Sprague-Dawley rat and compared with cyclosporine. Drugs were administered orally in a Cremophor-ethanol formulation for 14 days in two separate studies. RAPA, at 1 mg/kg, had no effect either functionally or histologically on the kidney. At 10 mg/kg, RAPA depressed the gain in body weight by 20% in the rat but had only minor functional disturbances on urine output, plasma creatinine, and creatinine clearance in the kidney. It did not induce any histomorphologic abnormalities. CsA, at 25 mg/kg, produced functional alterations in the kidney including elevated plasma creatinine and depressed clearance of creatinine as well as depressed body weight gain (17%). Histologically, CsA induced proximal tubule damage. These results demonstrate that RAPA (10 mg/kg) does not produce nephrotoxicity in the Sprague-Dawley rat at doses three times higher than its effective immunosuppressive doses established in the rat.     

Effect of tacrolimus (FK506) and sirolimus (rapamycin) mono- and combination therapy in prolongation of renal allograft survival in the monkey

BACKGROUND: Our previous studies confirmed that tacrolimus (FK506) and sirolimus [rapamycin (RAPA)], in combination, are not antagonistic but are synergistic in the prolongation of heart and small bowel grafts in the rodent. The aim of this study was to confirm further the synergistic effect of combined FK506 and RAPA in the more clinically relevant model, kidney transplantation in monkeys. METHODS: A total of 60 male Vervet monkeys were randomly assigned to 10 groups (n> or =5). Monkeys with renal allografts were treated with different doses of FK506 and/or RAPA orally for 60 days. Graft survival, body weight, clinical biochemistry determinations, oral glucose tolerance test, trough levels of the two drugs, and histopathology were investigated. RESULTS: Low doses of FK506 (1 or 4 mg/kg) combined with RAPA (0.5 mg/kg) produced synergistic effect in the prolongation of renal graft survival [combination index (CI) = 0.292, 0.565]. There were no additive or synergistic drug-associated toxicities such as hyperglycemia, nephrotoxicity, and hyperlipidemia. There also was no pharmacological antagonism. CONCLUSION: Concomitant therapy of low-dose (drug-optimal) FK506 and RAPA produced a synergistic effect in the prolongation of kidney allograft survival in Vervet monkeys without additive drug-associated toxicities.     

Effects of CS-866, an angiotensin II receptor antagonist, in 5/6 nephrectomized spontaneously hypertensive rats]

To assess the chronic antihypertensive and renal protective effects of the specific angiotensin II receptor antagonist, CS-866, in the remnant kidney model of chronic renal failure, we administered it alone or in combination with temocapril, an angiotensin converting enzyme inhibitor, to 5/6 nephrectomized spontaneously hypertensive rats (SHR) for 8 weeks. At the age of 10 weeks, 5/6 nephrectomized SHR were allocated to receive two doses of CS-866 (CS-3; 3 mg/kg/day, or CS-10; 10 mg/kg/day), temocapril (TEM; 10 mg/kg/day), a combination of CS-866 (3 mg/kg/day) and temocapril (10 mg/kg/day) or the vehicle alone via oral gavage for 8 weeks. Systolic blood pressure (SBP) and urinary protein excretion (UprotV) were measured every two weeks. At the age of 18 weeks, the rats were decapitated and the blood, remnant kidney, aorta and heart were collected and used for biochemical measurements and histopathological studies. There was no significant difference in body weight among the groups during the study. All drug treatments significantly reduced SBP, UprotV, glomerular sclerosis index (GSI), relative interstitial volume (RIV) and the heart weight to body weight ratio. The hypotensive effects were in the order of combination therapy > CS-10 = TEM > CS-3. For correlational analysis, we used values for SBP and UprotV derived from the average of values in rats over the age of 12 weeks through 18 weeks. UprotV, GSI and RIV were found to be highly correlated with SBP among the individual rats pooled from all groups (r = 0.511, r = 0.754, r = 0.817, respectively) and the correlation was maintained among the group means (r = 0.945, r = 0.989, r = 0.918, respectively). Furthermore, the heart weight to body weight ratio was found to be highly correlated with SBP among the individual rats pooled from all groups (r = 0.923) and the correlation was maintained among the group means (r = 0.996). We conclude that organ protective effects of CS-866, TEM, or combination therapy are closely related to the magnitude of their antihypertensive effects.     

Acute effects of different immunosuppressive drugs on pancreatic,islet, renal,and arterial hepatic blood flow in anesthetized rats

The effects of four different immunosuppressive drugs on organ blood flow were investigated. Sprague-Dawley rats were injected intravenously with 0.2 ml of either 15-deoxyspergualin (DSG; 5 mg/kg body weight), RS 61443 (80 mg/kg body weight), FK 506 (0.5 mg/kg body weight), cyclosporin A (9.5 mg/kg body weight), or the vehicles used. At 15 or 60 min after injection of the drugs, the blood perfusion of the whole pancreas, the pancreatic islets, and the kidneys, as well as the arterial blood flow to the liver, were measured in anesthetized animals using a microsphere technique. Fifteen minutes after administration, both FK506 and DSG decreased the fraction of whole pancreatic blood flow diverted through the islets. FK 506 and cyclosporin A reduced renal blood flow, but only 60 min after injection of the drug. None of the drugs influenced hepatic blood flow. RS 61443 did not affect the blood flow of the organ systems investigated. These differences in the effects of the drugs tested on blood flow might have some important implications on their efficacy and side effects. Thus, in view of its lack of influence on organ blood flow, RS 61443 seems to be preferable, at least when compared with cyclosporin A and FK 506 in the context of organ transplantation.     

Acute effects of rapamycin on glomerular dynamics: a micropuncture study in the rat

The acute effects of cyclosporin (CsA, 20 mg(kg i.v.) and rapamycin (RAPA, 5 mg(kg i.v.) on glomerular dynamics were separately investigated by renal micropuncture in two groups of intact rats (group CsA and RAPA, respectively) and compared with vehicle-treated rats, used as controls (group CON). Left kidney glomerular filtration rate (GFR) was decreased by CSA (-35% vs. CON, P<0.05), but was not affected by RAPA (-14% vs. CON, NS), whereas the single-nephron GFR (SNGFR) was significantly decreased in both groups (-40% in CsA, P<0.01 and -26% in RAPA, P<0.05 vs. CON). In both groups glomerular plasma flow (GPF) was significantly reduced vs. CON (CsA: -48%, and RAPA: -25%) due to the increase in both afferent (Ra) and efferent (Re) glomerular resistances: group CSA showed a prevalent rise in Re (+98% vs. CON, P<0.001) than in Ra (+66%, P<0.001); in group RAPA the increment was modest and similar in Ra and Re (+33 and +32%, respectively, NS versus CON). A further group of rats was studied in which L-Arginine (ARG), the precursor of nitric oxide (NO), was administered (2.5 mg/Kg/min iv) with RAPA (group ARG). ARG limited the rise in Ra and Re, thereby preserving GPF; nevertheless, SNGFR remained low (-26% vs. CON, P<0.05) due to the decrease in the effective filtration pressure (-26% vs. CON). These data demonstrate that: (1) CsA is nephrotoxic at immunosuppressive doses; (2) RAPA, even at huge doses, has marginal effects on renal and glomerular dynamics; (3) the ARG-NO pathway is only partially involved in the vasoconstriction of superficial nephrons after RAPA administration.     

Pharmacokinetic interactions augment toxicities of sirolimus/cyclosporine combinations

This study correlated the dynamic effects of sirolimus (rapamycin; RAPA) and cyclosporine (CsA) alone versus in combination to produce renal dysfunction, myelosuppression, or hyperlipidemia, with their corresponding blood and tissue concentrations. After salt-depleted rats were treated with RAPA (0.4 to 6.4 mg/kg per d) and/or CsA (2.5 to 20.0 mg/kg per d) for 14 d, the GFR, lipid levels, bone marrow cellularity, and CsA/RAPA concentrations in whole blood versus liver or renal tissues were measured, and the median effect model was used to discern the type of drug interactions. Compared with vehicle controls (1.98 +/- 0.34 ml/min), GFR values were reduced only by large doses of drug monotherapy, namely RAPA (3.2 mg/kg per d = 1.2 +/- 0.02 ml/min or 6.4 mg/kg per d = 1.3 +/- 0.2 ml/min; both P < 0.01) or CsA (10.0 mg/kg per d = 1.2 +/- 0.1 ml/min or 20.0 mg/kg per d = 0.8 +/- 0.4 ml/min; both P < 0.01). In contrast, hosts that were treated with smaller doses of CsA/RAPA combinations showed more pronounced effects in reduction of GFR values: 2.5/0.4 mg/kg per d, modestly (1.5 +/- 0.5 ml/min; P < 0.01); 5.0/0.8 mg/kg per d, moderately (0.23 +/- 0.01 ml/min; P < 0.001); and higher-dose groups, markedly. The exacerbation of renal dysfunction seemed to be due to a pharmacokinetic interaction of RAPA to greatly increase CsA concentrations in whole blood and, particularly, in kidney tissue. In contrast, the pharmacodynamic effects of CsA to potentiate two RAPA-mediated toxicities-myelosuppression and increased serum cholesterol/low-density lipoprotein cholesterol-occurred independently of pharmacokinetic interactions. RAPA aggravates CsA-induced renal dysfunction owing to a pharmacokinetic interaction, whereas CsA produces a pharmacodynamic effect that augments RAPA-induced myelosuppression and hyperlipidemia.     

Rapamycin rescue therapy in patients after kidney transplantation: first clinical experience

This study was aimed at analysing rapamycin (RAPA) rescue therapy with calcineurin inhibitor (CNI) withdrawal in renal transplant patients primarily presenting with CNI-nephrotoxicity (CNI-Neph), chronic allograft nephropathy (CAN) without [CAN(a)] and with histological changes suggestive of chronic rejection [CAN(b)]. In 36 patient with CNI-Neph (n = 6), CAN(b) (n = 21), CAN(a) (n = 7), and others (n = 2) RAPA therapy was started 4.4-115 months (median 30.6 months) after renal transplantation. During a follow up of 3-33 months (median 19 months) parameters of kidney function were recorded. Three patients on haemodialysis did not show any recovery of graft function. Of the remaining 33 patients renal function improved in 22 (66.7%), was stable in three (9%) but deteriorated in eight (24%) patients, of whom seven (21%) required haemodialysis thereafter. Success rate of RAPA therapy differed with respect to the histological diagnosis: 70% in CAN(b), 80% in CNI-Neph and 33% in CAN(a). Furthermore, in patients with creatinine levels above 400 mum (n = 6) graft function rarely improved (n = 2, 33%). The RAPA rescue therapy with CNI withdrawal appears promising in a special cohort of patients with chronic renal allograft dysfunction even late after transplantation.     

Cyclosporine Withdrawal Improves Renal Function in Heart Transplant Patients on Reduced-Dose Cyclosporine Therapy

Renal failure is a major cause of morbidity after heart transplantation. It is unclear whether calcineurin inhibitor (CNI) free immunosuppression provides more nephroprotection than low-dose CNI therapy. Thirty-nine patients with renal failure on low-dose cyclosporine A (CsA) were studied (62.9 +/- 8.7 years, five female, 8.2 +/- 4.3 years posttransplant, serum creatinine: 1.9 +/- 0.3 mg/dL, calculated GFR (cGFR): 48.2 +/- 18.3 mL/min, CsA C0 level: 64.0 +/- 19.9 ng/mL). All patients had been treated with low-dose CsA >6 months, renal function was stable or slowly decreasing (creatinine 1.7-3.5 mg/dL). Nineteen patients were randomized to discontinuation of CsA and overlapping rapamycin therapy initiation (RAPA), 20 patients continued low-dose CsA (control). Three patients (16%) discontinued rapamycin medication for side effects (diarrhea, skin rash), two patients developed pneumonia and pulmonary embolism, respectively, no rejection or other infectious complications were seen. After 6 months, renal function in the control group was unchanged. In the RAPA group, renal function markedly improved (creatinine: 2.08 +/- 0.15 to 1.67 +/- 0.13 mg/dL, cGFR: 48.5 +/- 21.4 to 61.7 +/- 21.4 mL/min (p < 0.001 within and between groups)). In carefully selected late survivors following heart transplantation who are at low risk of rejection, CNI-free rapamycin-based immunosuppression improves cGFR even in those already receiving low-dose CsA therapy. The results of this study warrant further confirmation in larger clinical trials that are powered to assess clinical outcomes.     

Testicular gametogenic and steroidogenic activities in chlorpyrifos insecticide-treated rats: a correlation study with testicular oxidative stress and role of antioxidant enzyme defence systems in Sprague-Dawley rats

The present works examined an adverse effect of chlorpyrifos insecticide on testes and lipid peroxidation at low doses (5 mg-10 mg kg(-1) body weight) and the role of antioxidant enzymes systems at higher doses (20-30 mg kg(-1) body weight) in albino rats. At low doses, reduction in plasma levels of testosterone and FSH and LH hormones along with the significant shrinkage of seminiferous tubules and gametogenic changes in germ cells were noticed. But these changes were restored with the revival of serum testosterone, FSH and LH along with regression of testis at higher doses. Similarly, level of testicular lipid peroxidation was elevated, whereas levels of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) and steroidogenic enzymes activities (Δ(5) , 3β-hydroxysteroid dehydrogenase and 17β-hydroxysteroid dehydrogenase) were reduced significantly at low doses. But, rat testes showed a significant decrease in lipid peroxidation and concomitant increase in antioxidant enzymes and steroidogenic enzymes activities at higher doses. Results showed that at higher doses of chlorpyrifos treatments, rat testes were shown to trigger their natural defence mechanism which became operative possibly through corrective measure of synthesis of antioxidant defence enzymes and steroidogenic enzymes and pituitary gonadotrophins hormone feedback mechanisms.     

The effects of disodium ethane-1-hydroxy-1, 1-diphosphonate (EHDP) on mineral and organic components of rat bone

The purpose of this study was to determine the short-term effects of various systemic doses of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on bone organic matrix and to relate these effects to the corresponding dose-related changes in bone mineral. EHDP was administered daily by subcutaneous injection at doses of 0.25, 2.5 and 40 mg/kg body weight for periods of one and two weeks. At both time intervals, rat tibiae were quantitatively analyzed for mineral content (ash, calcium and phosphorus) and for organic matrix content (matrix weight, nitrogen and certain amino acids). The latter data were correlated with semiquantitative histological analyses of the tibiae. Results of this study demonstrate that the short term effects of EHDP on bone chemistry and histology are variable and depend on the systemic dose and the duration of treatment. Systemic doses of 0.25 and 2.5 mg/kg EHDP following daily administration for one week resulted in transitory decreases in bone mineral content compared to controls. Following two weeks of treatment, both of these dose levels resulted in increased bone mineral content and, in addition, the 2.5 mg/kg dose resulted in tibiae which contained more organic matrix compared to control bones. In contrast to the low dose effects, a high systemic dose of EHDP—e.g. 40 mg/kg administered daily for 1 or 2 weeks—appears to act solely by inhibiting mineralization of newly-formed matrix.     

Effect of cyclosporin A,azathioprine, and prednisolone on carbohydrate metabolism of rat hepatocytes

The effect of different immunosuppressive drugs (prednisolone, azathioprine, cyclosporin A) on liver carbohydrate metabolism in the rat was investigated. Daily administration of prednisolone (3 mg/kg body weight) and azathioprine (2 mg/kg body weight) intraperitoneally for 2 weeks caused significantly lower liver glycogen content than that in NaCl-treated controls. Liver glucose and lactate content, as well as plasma glucose, glucagon, and serum insulin concentration of these animals, remained unchanged. There were no differences in any of these parameters between cyclosporin A (15 mg/kg body weight)-treated and vehicle (olive oil/ethanol)-treated animals. Prednisolone caused significantly lower glucose production in isolated rat hepatocytes using Na-pyruvate as the substrate, whereas glucose production was unchanged in hepatocytes of azathioprine-treated rats using pyruvate or l-serine as substrates. Glucose production from pyruvate or serine was significantly inhibited by cyclosporin A compared to the vehicle, but did not differ from the effects of azathioprine and prednisolone. Lactate production was significantly lower in cyclosporin-treated animals than in those given either the vehicle or azathioprine. Cyclosporin A completely reversed the inhibition of hepatocyte glycogen consumption caused by the vehicle. However, glycogen production in the presence of cyclosporin A was comparable to the effects of prednisolone and azathioprine. Finally, hepatocyte ketone body production using pyruvate as the substrate was higher in the presence of all immunosuppressive drugs. In the presence of serine, acetoacetate production increased in rats treated with 50 mg/kg body weight cyclosporin A, and -hydroxybutyrate production in animals receiving 15 and 50 mg/kg body weight cyclosporin A.This article is dedicated to Professor K. Kochsiek, Chief of the Medical Department, University of Würzburg, FRG, on the occasion of his 60th birthday     

Protective effect of the PAF antagonist BN 52021 in an experimental renal warm ischemia model

Platelet activating factor is involved in warm ischemic damage. We studied the effect of the PAF receptor antagonist BN 52021 in an experimental model of 60 min of renal warm ischemia in which the left kidney was flushed with Euro-Collins solution and a right nephrectomy was performed. Eighty Wistar rats were divided into a sham-operated group, two control groups, and four study groups, according to the dosage and route of BN 52021 administration. BN 52021 was used in the flush solution at concentrations of 0.1 and 0.5 mg/ml, or intravenously prior to ischemia at 5 and 10 mg/kg body weight. Creatinine clearance per, 100g body weight, fractional sodium excretion, and conventional histology were studied. Rats that received BN 52021 intravenously showed a significantly higher creatinine clearance than controls. Intravenous BN 52021 produced a higher acceleration of renal function recovery at 10 mg/kg than at 5 mg/kg body weight. Conventional histology was better in animals that received BN 52021 at 10 mg/kg body weight than in controls. Addition of BN 52021 to Euro-Collins flushing solution showed no protective effect. We conclude that intravenous BN 52021 shows a renal protective effect against warm ischemia.     

Effect of hepatocyte growth factor on tacrolimus-induced nephrotoxicity in spontaneously hypertensive rats

Renal toxicity is a serious side effect of therapy with tacrolimus (FK506), an immunosuppressive agent administered to renal transplant recipients. We investigated the effect of hepatocyte growth factor (HGF) on tacrolimus-induced nephrotoxicity in spontaneously hypertensive rats (SHR). After a right nephrectomy, rats received a continuous perfusion of either HGF in a dose of 5 μg/kg daily (tacrolimus + HGF group) or normal saline (tacrolimus group) into the left renal artery at a rate of 1 μl/h for 7 days after surgery. Tacrolimus was injected intramuscularly in a dose of 4 mg/kg daily for 10 days after surgery. HGF significantly inhibited the tacrolimus-induced increase in the serum creatinine (SCr) level (P < 0.05). HGF also prevented the tacrolimus-induced loss in body weight. The bromodeoxyuridine (BrdU) index was significantly higher in kidney specimens from the tacrolimus + HGF group. These findings suggest that HGF induces the regeneration of renal tubular cells and suppresses tacrolimus-induced renal toxicity in SHR. Received: 26 February 1998 Received after revision: 25 August 1998 Accepted: 23 September 1998     

Effect of mTOR inhibitor on body weight: from an experimental rat model to human transplant patients

The aim was to study the influence of sirolimus (SRL) on body weight in a rat model and in kidney transplant patients. Wistar rats (15 weeks old) were either treated with vehicle (VEH; n = 8) or SRL (n = 7) 1.0 mg/kg three times per week for 12 weeks. Body mass and food intake were measured weekly. Adipocyte diameter was determined in hematoxylin–eosin stains. The body mass index (BMI) obtained from clinical kidney transplant trials comparing SRL‐based with cyclosporine‐based therapy was analyzed. Animals: SRL produced a decrease of the weight gain curve. At the end of the study, mean body weight in the SRL group was lower than in the VEH group (356 vs. 507 g, P < 0.01) in spite of comparable food intake normalized for body weight was not different. Mean adipocyte diameter was 36 μm in VEH and 25 μm in SRL rats (P = 0.009). Mean SRL blood trough concentration was 38 ng/ml. Kidney transplant patients: Two years after transplantation, BMI was significantly lower in the SRL‐based treatment arm compared to cyclosporine (24.17 ± 2.99 vs. 25.97 ± 5.01 kg/m², P = 0.031). SRL treatment leads to less body mass. Adipocyte cell diameter was reduced in SRL‐treated animals. A possible explanation may be the effects of SRL on metabolic regulation and cell growth.     

Effects of immunosuppressant FTY720 on renal and hepatic hemodynamics in the rat

BACKGROUND: FTY720 is a novel immunomodulator that may provide an opportunity for a reduction in calcineurin inhibitor dosage in transplant recipients with renal/hepatic side effects. However, the effects of FTY720 on renal or hepatic hemodynamics are unknown. The aim of this study was to establish the hemodynamic and renal actions of FTY720 at therapeutically relevant dosages. METHODS: The effects of acute and repeat oral administration of FTY720 on systemic, renal, and hepatic hemodynamics were investigated in the anesthetized male Lewis rat. Renal function and renal tubular parameters were examined in animals that received repeat high dosage of FTY720. RESULTS: Seven-day oral administration of FTY720 did not cause any significant changes in markers of hepatocyte injury, nor did it cause any reduction in renal function (elevated urea and creatinine). Histological examination of liver and kidney from animals treated with repeat FTY720 for 1 or 3 weeks did not reveal any sclerosis, tubular changes, infiltrates, or fibrosis. Hepatocyte, vascular, and biliary structures were normal. Compared with the vehicle (saline), oral administration of FTY720 at dosages up to 5 mg/kg/day for 1 week did not have any significant effects on systemic, hepatic, or renal hemodynamics. Five min after intravenous FTY720 administration (1 mg/kg), mean arterial pressure (MAP) rose to 114+/-3.3% of baseline (P <0.01) before returning to the normal range within 30-45 min. Lower doses of FTY720 (0.3 and 0.5 mg/kg, i.v.) did not affect MAP. Renal cortical perfusion, renal artery blood flow, and renal vascular resistance were not altered by FTY720 at i.v. doses up to 1 mg/kg. Animals that received FTY720 (5 mg/kg/day) for 3 weeks showed a significant reduction in body weight (-4.8+/-1% of baseline at 3 weeks, P <0.001); however, weight-adjusted creatinine clearance, 24 h urine production, and urine osmolality were not different from those in control animals (0.71+/-0.1 vs. 0.74+/-0.1 ml/min/100 g, 2.63+/-0.2 vs. 3.12+/-0.2 ml/100 g, and 2003+/-33 vs. 1966+/-56 mOsm/kg, respectively). FTY720 at the same repeat oral dosage was, nevertheless, associated with a significantly lower 24 h sodium excretion and a significantly lower fractional excretion of sodium compared with those in control animals (223.4+/-35 vs. 304.5+/-50 micromol/100 g and 1.75+/-0.3 vs. 2.23+/-0.3%, respectively; P <0.05). CONCLUSIONS: Our data indicate that, at least in the short term, oral FTY720 does not cause any significant adverse effects on renal or hepatic hemodynamics, nor does it cause any reduction in glomerular perfusion and thus may provide reasonable rescue/add-on therapy in calcineurin-inhibitor treated transplant recipients. At high repeat oral dosages, however, FTY720 may alter renal handling of sodium.     

Prolongation of discordant renal xenograft survival by depletion of complement. Comparative effects of systemically administered cobra venom factor and soluble complement receptor type 1 in a guinea-pig to rat model

Abstract There is an increasing body of evidence to suggest that inhibition of complement activation may be a valuable approach to avert hyperacute rejection. In our study, the guinea-pig to rat discordant kidney xenograft model was adapted for the investigation of renal transplant function and an attempt was made to delay the hyperacute rejection using systemically administered cobra venom factor (CVF) and soluble complement receptor type 1 (sCR1). The saline-treated control recipients experienced a rapid transplant rejection with a xenograft survival averaging 10.5 ± 2.1 min. Administration of a single 60 U/kg i. v. bolus of CVF significantly prolonged renal graft survival to 20.4 ± 2.5 h, and by a single bolus of sCR1 (50 mg/kg) a prolongation of graft survival to 18.8 ± 2.3 h was achieved. The grafts functioned only over periods of 2.5 ± 0.3 and 2.3 ± 0.2 h, respectively. No complications of sCR 1 were noted. We concluded that complement inhibition by sCR 1 may be an important component in the therapeutic approach aiming at the prevention of hyperacute rejection in human organ transplantation.     

Effect of angiotensin-converting enzyme inhibition on renal filtration surface area in hypertensive rats.

BACKGROUND: Angiotensin-converting enzyme (ACE) inhibitor treatment leads to protective effects on the cellular structure of the glomerulus and the kidney. The aim of this study was to determine whether ACE inhibition increases renal filtration surface area in the spontaneously hypertensive rat (SHR). METHODS: SHR were treated with the ACE inhibitor perindopril at a high dose (3 mg/kg/day) or a low dose (0.1 mg/kg/day) during the period of hypertension development, from 7 to 14 weeks of age. Some animals were treated concomitantly with the bradykinin B2 receptor antagonist, S16118. Tail-cuff systolic blood pressure and body weights were measured twice weekly. At termination of treatment, glomerular number and volume, length, and surface area of glomerular capillaries and renal filtration surface area were estimated using unbiased stereological techniques. RESULTS: There were significant dose-related reductions in blood pressure with high- and low-dose perindopril treatment. Neither low- nor high-dose perindopril treatment had any effect on glomerular number or size or glomerular capillary length and surface area. Hence, there was no significant difference in total renal filtration surface area between any of the experimental groups (8721 +/- 610 mm2 in untreated SHR and 7879 +/- 338 mm2 and 8767 +/- 437 mm2 in the low and high dose perindopril-treated groups, respectively). Coadministration of the bradykinin antagonist did not affect any of the glomerular parameters. CONCLUSIONS: ACE inhibition during the period of hypertension development does not lead to an enhanced glomerular capillary growth or increases in total renal filtration surface area in this model.     

Comparative efficacy of mycophenolate sodium (MPS) and mycophenolate mofetil (MMF) with and without cyclosporine in rat transplantation models.

BACKGROUND: ERL is the enteric-coated sodium salt of mycophenolic acid, presently in clinical development. The drug substance mycophenolate sodium (MPS) was evaluated in rat transplantation models and compared with mycophenolate mofetil (MMF) for therapeutic window and synergy with cyclosporine (CsA). METHODS: Allotransplantation was performed in the Dark Agouti-to-Lewis (DA-to-Lewis; kidney, heart, and aorta) and Brown Norway-to-Lewis (BN-to-Lewis; kidney) strain combinations, and hamster heart xenotransplantation was performed in athymic and euthymic Lewis rats. The compounds were administered daily orally, starting the day of transplantation. RESULTS: In kidney and heart transplantation the minimal efficacious dose of CsA was 5.0 mg/kg/d. For MPS this dose was 10 mg/kg/d in BN-to-Lewis kidney transplantation, 20 mg/kg/d in DA-to-Lewis heart transplantation, and 10 mg/kg/d in hamster-to-athymic rat heart transplantation. At these doses the first signs of adverse effects were evident, indicating a narrow therapeutic window. No window was established for MMF in these models or for MPS in DA-to-Lewis kidney transplantation. There was no potential synergy between CsA and MPS or MMF regarding efficacy, but fewer side effects were noted in efficacious combinations, in particular for MPS. In aorta transplantation, MPS and MMF dose-dependently inhibited intima thickening. The combination of 20 mg/kg/d MPS and 10 mg/kg/d CsA gave long-term survival of hamster-to-rat xenografts. CONCLUSIONS: Despite the overall comparable efficacy and narrow therapeutic window of MPS and MMF when given alone, MPS apparently is better tolerated than MMF in some of the transplant models. The combination of these agents with CsA allows fine-tuning between optimal immunosuppression and adverse side effects.     

Immunosuppressive activity of the Chinese medicinal plant Tripterygium wilfordii. I. Prolongation of rat cardiac and renal allograft survival by the PG27 extract and immunosuppressive synergy in combination therapy with cyclosporine

BACKGROUND: PG27 is an immunosuppressive fraction purified from an extract of a Chinese medicinal plant, Tripterygium wilfordii. We tested PG27 in rat cardiac and renal allotransplantation, and we examined the immunosuppressive interaction with cyclosporine (CsA). METHODS: Brown Norway (BN) rat heart or kidney allografts were transplanted into the abdomen of Lewis rats, which were treated by the intraperitoneal or oral route with PG27, CsA, or both. RESULTS: PG27 administered intraperitoneally to Lewis recipients for 16 days at 10-30 mg/kg/day significantly increased the median survival time of BN heart allografts from 7 to 18-22 days. Oral administration was effective, with cardiac allograft survival prolonged to > 100 days with 52 days of treatment. PG27 at 20-30 mg/kg/day significantly extended the median survival time of BN kidney allograft recipients from 9 to 36.5-77 days, and 30 mg/kg/day for 52 days extended survival beyond 200 days. PG27 combined with CsA significantly enhanced heart and kidney allograft survival, even at doses of CsA ineffective when administered alone. The addition of 5 or 10 mg/kg/day PG27 reduced by 50-75% the CsA dose needed for 100% kidney allograft survival. The combination index was less than 1.0, indicating synergy of PG27 with CsA in prolonging cardiac and renal allograft survival. Furthermore, the PG27/CsA combination exerted a positive influence on renal allograft function. PG490 (triptolide, a constituent of PG27) and PG490-88 (a semisynthetic derivative of PG490) suppressed rejection of cardiac and renal allografts. CONCLUSIONS: The PG27 herbal extract demonstrated immunosuppressive activity by prolonging heart and kidney allograft survival, displaying synergy in the immunosuppressive interaction with CsA, and improving renal allograft function in combination with CsA. PG490 and PG490-88 compounds were also effective.