Volume 8, Number 3, September 2007

PAPERIn vivo effect of enalapril on lysosomal compartment isolated from kidney and liver of rats
Reinaldo Martinelli, Claudia VCD Santos, Marcel L Albuquerque, Aline M Silva, Luiz Erlon Rodrigues

Introduction: Angiotensin II (Ang II) inhibitory agents such as angiotensin-converting enyzme (ACE) inhibitors have been used as antihypertensive and anti-proteinuric drugs, attenuating the progression and inducing regression of glomerulosclerosis. The mechanisms related to the renoprotective effects of the ACE-inhibitors, although partly related to the blockade of the renin-angiotensin system (RAS), are not completely understood. Their effects on many cellular functions and intracellular components have not been directly studied. The aim of the present studies was to investigate the effect of enalapril on lysosomal activity.
Material and methods: Two groups of Wistar rats were studied. The experimental group received enalapril, 50 mg/L, in the drinking water; the control group was submitted to the same conditions except for enalapril. After two weeks of treatment, each animal was sacrificed and samples of liver and kidney were individually collected, homogenised and subjected to differential centrifugation. The supernatant was utilised for evaluation of ortophosphoric-monoester phosphohydrolase as a marker of lysosome stability and the results expressed as specific units of phosphatase activity. Results The mean specific activities of the lysosomal compartment isolated from kidneys of enalapril-treated rats showed a mean specific activity that was 17.6% higher than the control group; no: difference was found in the liver.
Conclusion. The present studies suggests that the beneficial effect of enalapril is not related to effects on lysosomal membrane.

JRAAS 2007;8:105-109.

PAPERAngiotensin II receptor blockade blocker pre-treatment largely prevents injury from gradual renal ablation in rats
Hye Won Park, Youngki Kim, Kee Hyuck Kim, Hyeon Joo Jeong, Myung-Hee Shin, Silvia Rozen, Michael Mauer

Introduction: Reduction in renal mass in rats results in progressive proteinuria, hypertension, focal-segmental glomerulosclerosis (FSG), atrophy of tubules (AT), and interstitial expansion. We reported that slow reduction of renal tissue in rats (slow ablation) ending in the removal of 1.5 kidneys is associated, over the next six months, with higher albumin excretion rates (AER) and accelerated development of FSG lesions compared to sudden equivalent renal mass reduction. It was hypothesised that slow reduction of nephron numbers allows for a process of conditioning of residual nephrons that increases their susceptibility to subsequent injury.
Methods: To test this idea we treated Münich-Wistar rats with the angiotensin receptor blocker (ARB) losartan for six weeks during the gradual staged surgical removal of 1.5 kidneys, and compared them to sham operated controls, and parallel groups untreated by losartan.
Results: Despite discontinuation of losartan over the subsequent six months, ARB pre-treatment completely prevented proteinuria and hypertension in these slow renal ablation rats. ARB pre-treatment also largely prevented the subsequent development of FSG, AT, and interstitial expansion in these animals. Both losartan-treated and untreated renal ablation groups had glomerular enlargement and compensatory hyperfiltration and this was uninfluenced by losartan.
Conclusion: Temporary ARB administration during gradual renal mass reduction resulted in long-term prevention of hypertension and albuminuria and greatly reduced FSG and tubular and interstitial lesions. We hypothesise that the preconditioning of residual nephrons in the gradual ablation model which facilitates their subsequent injury, is blunted by renin-angiotensin system blockade.

JRAAS 2007;8:110-117.

POPULAR
TOPICPAPERBeneficial effects of spironolactone on glomerular injury in streptozotocin-induced diabetic rats
Jun Yuan, Ruhan Jia, Yan Bao

Introduction: To investigate the beneficial effects of spironolactone (SPL) on glomerular injury in streptozotocin (STZ)-induced diabetic rats and the possible mechanism.
Methods and results: STZ-induced diabetic rats were divided into control group, STZ group, and SPL group. Glomerular morphology was observed by light microscopy after the rats were sacrificed after 30 days treatment. The mRNA expressions of transforming growth factor-beta 1 (TGF-β₁) and type-1 plasminogen activator inhibitor (PAI-1) in renal cortex were measured by transcription-polymyerase chain reaction (RT-PCR). The protein expressions of PAI-1, fibronectin (FN) and TGF-β₁ were detected by western blotting and immunohistochemistry respectively. In addition, levels of malondialdehyde (MDA) and the activity of antioxidants including superoxide diamutase (SOD), glutathione peroxidase (GSH-P_X) in the cortex of kidney were measured.
Results: In untreated diabetic rats, the glomerular volume, the expression of FN and the urinary albumin excretion increased. The mRNA and protein expression of PAI-1 and TGF-β₁ significantly increased in the STZ group. Treatment with SPL partially reversed these changes. Meanwhile, elevated MDA levels as well as decreased SOD and GSH-P_X activities in the cortex of kidney were significantly ameliorated in the treated group.
Conclusion: SPL ameliorates the glomerular injury in STZ-induced early diabetic renal injury, which is closely related with the reduction of PAI-1 and TGF-β₁ expression and the attenuation of oxidative stress.

JRAAS 2007;8:118-126.

POPULAR
TOPICPAPERAngiotensin type 1 receptor blockade prevents endocardial dysfunction of rapidly paced atria in rats
Takeshi Yamashita, Akiko Sekiguchi, Takeshi Kato, Takayuki Tsuneda, Yu-ki Iwasaki, Kouichi Sagara, Hiroyuki Iinuma, Hitoshi Sawada, Tadanori Aizawa

Introduction: Atrial fibrillation (AF) per se causes atrial endocardial dysfunction leading to local coagulation imbalance on the internal surface of the atrium, which contributes to thrombus formation in the fibrillating left atrium.
Materials and methods: To test a hypothesis that blockade of angiotensin II type 1 receptor (AT₁-receptor) prevents the endocardial dysfunction by AF, we examined the effects of olmesartan on the expression of tissue factor pathway inhibitor (TFPI), thrombomodulin (TM), endothelial nitric oxide synthase (eNOS) and plasminogen activator inhibitor-1 (PAI-1) in the endocardium of the rapidly paced rat atria.
Results: Rapid pacing induced a significant decrease in TFPI, TM and eNOS and an increase in PAI-1 protein in the left atrium. Pre-administration of low-dose olmesartan significantly prevented the down-regulation of TFPI, TM and eNOS and also attenuated the up-regulation of PAI-1. Immunohistochemistry identified these changes predominantly in the atrial endocardium. While the drug was without any effect on mRNA levels of TFPI, TM and eNOS, there was a significant decrease in its PAI-1 mRNA expression.
Conclusions: AT₁-receptor blocker could partially prevent the atrial endocardial dysfunction by rapid atrial pacing, which would provide one theoretical basis for beneficial effects for stroke prevention in AF.

JRAAS 2007;8:127-132.

PAPERInteractions of angiotensin IV and oxytocin on behaviour in mice
Paul R Gard, Pauline Daw, Zhila Sayyad Mashhour, Paula Tran

Introduction: Angiotensin (Ang) IV enhances learning and memory in rats but there are strain differences in its effects in mice. Oxytocin (OT) also influences learning and memory in rats and mice and, in the light of the proposed effects of Ang IV on oxytocinase, the hypothesis that the effects of Ang IV on cognition in mice involve OT was tested.
Materials and methods: The effects of Ang IV and OT, alone and combined, were determined in rat isolated uterine smooth muscle and in object recognition and forced swim tests in BKW mice.
Results: Ang potentiated the contractile effects of OT in the uterus. Neither peptide had any effect on object recognition nor locomotor activity. Ang IV had no effect in the forced swim test but abolished the effects of OT.
Conclusions: Ang IV influences the actions of OT in vitro and in vivo, possibly by inhibition of oxytocinase, but the lack of effect of Ang IV on object recognition in BKW mice is unlikely to be a consequence of a deficiency endogenous OT. Unlike OT, Ang IV alone has no effect on learned helplessness in the forced swim test, an effect often used to predict potential antidepressant efficacy in humans.

JRAAS 2007;8:133-138.

PAPEREfficacy and tolerability of candesartan cilexetil/hydrochlorothiazide and amlodipine in patients with poorly controlled mild-to-moderate essential hypertension
Roberto Fogari, Amedeo Mugellini, Giuseppe Derosa on behalf of the CANDIA (CANdesartan and DIuretic vs Amlodipine in hypertensive patients) Study Group

The antihypertensive efficacy and tolerability of combination therapy with candesartan cilexetil, 16 mg plus hydrochlorothiazide (CC/HCTZ), 12.5 mg was compared with that of amlodipine, in a multicentre, double-blind, randomised, parallel-group study in patients with mild-to-moderate essential hypertension inadequately controlled by monotherapy. After a two week run-in period on existing therapy, patients with a sitting diastolic blood pressure (DBP) of 90–110 mmHg and a sitting systolic blood pressure (SBP) < 180 mmHg were switched to either CC/HCTZ (n=101) or amlodipine (n=102), once-daily by mouth. After eight weeks of treatment, both regimens reduced mean trough blood pressure (BP) by a similar amount: mean sitting SBP/DBP reductions were -15.4/-11.9 mmHg for CC/HCTZ, and -15.7/-12.0 mmHg for amlodipine (group differences, p=0.835/0.963). The BP of 84.2% of patients on CC/HCTZ and 84.5% on amlodipine was controlled (sitting DBP < 90 mmHg and sitting SBP < 140 mmHg) (p=1.00). Six (5.9%) patients on CC/HCTZ and 18 (17.6%) on amlodipine discontinued treatment, including one (1%) and 12 (11.8%) owing to adverse events (p<0.001). The most common adverse event was peripheral oedema, which occurred in two patients on CC/HCTZ and 19 on amlodipine. In conclusion, CC/HCTZ and amlodipine were equally effective in reducing BP in hypertensive patients not controlled by monotherapy, but CC/HCTZ was much better tolerated. Tolerance is an important clinical consideration in the chronic treatment of an asymptomatic disease.

JRAAS 2007;8:139-144.

POPULAR
TOPICRENIN REPORTMechanisms of hypertension-induced target organ damage
Dominik N Müller

JRAAS 2007;8:148-150.

POPULAR
TOPICCOMMUNICATIONRenin-angiotensin system expression in the K562 human erythroleukaemic cell line
Ebru Koca, Ibrahim C Haznedaroglu, Kadir Acar, Yavuz Beyazit, Salih Aksu, Muge Misirlioglu, Serdar Tuncer, Nilgun Sayinalp, Osman I Ozcebe, Aysegul Uner

Local renin-angiotensin system (RAS) may affect leukaemic cell production within the bone marrow microenvironment. Angiotensin-converting enzyme (ACE), renin, and angiotensin could influence leukaemogenesis. In this study, mRNA expressions of the major RAS components (ACE, renin, and angiotensinogen) in K562 human erythroleukaemia cell line have been searched by Real Time quantitative polymerase chain reaction. K562 blasts are multipotential, haematopoietic malignant cells that spontaneously differentiate into recognisable progenitors of the erythrocyte, granulocyte and monocytic series. We observed significant expressions of ACE, renin, and angiotensinogen in K562 leukaemic blast cells. Therefore, K562 human erythroleukaemia cell line may serve as an in vitro model to elucidate the role of RAS in leukaemia and to test the effects of RAS-affecting drugs on leukaemic cellular proliferation.

JRAAS 2007;8:145-147.