Aldosterone nongenomically induces angiotensin II receptor dimerization in rat kidney: role of mineralocorticoid receptor and NADPH oxidase.

INTRODUCTION: Previous in vitro studies demonstrated that aldosterone nongenomically induces transglutaminase (TG) and reactive oxygen species (ROS), which enhanced angiotensin II receptor (ATR) dimerization. There are no in vivo data in the kidney. MATERIAL AND METHODS: Male Wistar rats were intraperitoneally injected with normal saline solution, or aldosterone (Aldo: 150 µg/kg BW); or received pretreatment with eplerenone (mineralocorticoid receptor (MR) blocker, Ep. + Aldo), or with apocynin (nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, Apo. + Aldo) 30 min before aldosterone. Thirty minutes after aldosterone injection, protein abundances of dimeric and monomeric forms of AT1R and AT2R, and protein abundances and localizations of TG2 and p47phox, a cytosolic subunit of NADPH oxidase, were determined by Western blot analysis and immunohistochemistry, respectively. RESULTS: Protein abundances of dimeric forms of AT1R and AT2R were enhanced by 170% and 70%, respectively. Apocynin could block dimeric forms of both receptors while eplerenone inhibited only AT2R. Monomeric protein levels of both receptors were maintained. Aldosterone significantly enhanced TG2 and p47phox protein abundances, which were blunted by eplerenone or apocynin. Aldosterone stimulated p47phox protein expression in both the cortex and the medulla while TG2 was induced mostly in the medulla. Eplerenone or apocynin normalized the immunoreactivity of both TG2 and p47phox. CONCLUSIONS: This is the first in vivo study demonstrating that aldosterone nongenomically increases renal TG2 and p47phox protein expression and then activates AT1R and AT2R dimerizations. Aldosterone-stimulated AT1R and AT2R dimerizations are mediated through activation of NADPH oxidase. Aldosterone-induced AT1R dimer formation is an MR-independent pathway, whereas the formation of AT2R dimer is modulated in an MR-dependent manner.

Aldosterone Rapidly Enhances Levels of the Striatin and Caveolin-1 Proteins in Rat Kidney: The Role of the Mineralocorticoid Receptor.

BACKGROUND: Striatin and caveolin-1 (cav-1) are scaffolding/regulating proteins that are associated with salt-sensitive high blood pressure and promote renal sodium and water reabsorption, respectively. The mineralocorticoid receptor (MR) interacts with striatin and cav-1, while aldosterone increases striatin and cav-1 levels. However, no in vivo data have been reported for the levels of these proteins in the kidney. METHODS: Male Wistar rats were intraperitoneally injected with normal saline solution, aldosterone alone (Aldo: 150 µg/kg body weight), or aldosterone after pretreatment with eplerenone, an MR blocker, 30 minutes before the aldosterone injection (eplerenone [Ep.]+Aldo). Thirty minutes after the aldosterone injection, the amount and localization of striatin and cav-1 were determined by Western blot analysis and immunohistochemistry, respectively. RESULTS: Aldosterone increased striatin levels by 150% (P<0.05), and cav-1 levels by 200% (P<0.001). Eplerenone had no significant effect on striatin levels, but partially blocked the aldosterone-induced increase in cav-1 levels. Aldosterone stimulated striatin and cav-1 immunoreactivity in both the cortex and medulla. Eplerenone reduced cav-1 immunostaining in both areas; however, striatin intensity was reduced in the cortex, but increased in the medulla. CONCLUSION: This is the first in vivo study demonstrating that aldosterone rapidly enhances renal levels of striatin and cav-1. Aldosterone increases striatin levels via an MR-independent pathway, whereas cav-1 is partially regulated through MR.

Aldosterone rapidly activates p-PKC delta and GPR30 but suppresses p-PKC epsilon protein levels in rat kidney.

OBJECTIVES: Aldosterone rapidly enhances protein kinase C (PKC) alpha and beta1 proteins in the rat kidney. The G protein-coupled receptor 30 (GPR30)-mediated PKC pathway is involved in the inhibition of the potassium channel in HEK-239 cells. GPR30 mediates rapid actions of aldosterone in vitro. There are no reports available regarding the aldosterone action on other PKC isoforms and GPR30 proteins in vivo. The aim of the present study was to examine rapid actions of aldosterone on protein levels of phosphorylated PKC (p-PKC) delta, p-PKC epsilon, and GPR30 simultaneously in the rat kidney. METHODS: Male Wistar rats were intraperitoneally injected with normal saline solution or aldosterone (150 µg/kg body weight). After 30 minutes, abundance and immunoreactivity of p-PKC delta, p-PKC epsilon, and GPR30 were determined by Western blot analysis and immunohisto-chemistry, respectively. RESULTS: Aldosterone administration significantly increased the renal protein abundance of p-PKC delta by 80% (p<0.01) and decreased p-PKC epsilon protein by 50% (p<0.05). Aldosterone injection enhanced protein immunoreactivity of p-PKC delta but suppressed p-PKC epsilon protein intensity in both kidney cortex and medulla. Protein abundance of GPR30 was elevated by aldosterone treatment (p<0.05), whereas the immunoreactivity was obviously changed in the kidney cortex and inner medulla. Aldosterone translocated p-PKC delta and GPR30 proteins to the brush border membrane of proximal convoluted tubules. CONCLUSIONS: This is the first in vivo study simultaneously demonstrating that aldosterone administration rapidly elevates protein abundance of p-PKC delta and GPR30, while p-PKC epsilon protein is suppressed in rat kidney. The stimulation of p-PKC delta protein levels by aldosterone may be involved in the activation of GPR30.

Vanadate-Induced Renal cAMP and Malondialdehyde Accumulation Suppresses Alpha 1 Sodium Potassium Adenosine Triphosphatase Protein Levels.

It has been demonstrated that vanadate causes nephrotoxicity. Vanadate inhibits renal sodium potassium adenosine triphosphatase (Na, K-ATPase) activity and this is more pronounced in injured renal tissues. Cardiac cyclic adenosine monophosphate (cAMP) is enhanced by vanadate, while increased cAMP suppresses Na, K-ATPase action in renal tubular cells. There are no in vivo data collectively demonstrating the effect of vanadate on renal cAMP levels; on the abundance of the alpha 1 isoform (α1) of the Na, K-ATPase protein or its cellular localization; or on renal tissue injury. In this study, rats received a normal saline solution or vanadate (5 mg/kg BW) by intraperitoneal injection for 10 days. Levels of vanadium, cAMP, and malondialdehyde (MDA), a marker of lipid peroxidation were measured in renal tissues. Protein abundance and the localization of renal α1-Na, K-ATPase was determined by Western blot and immunohistochemistry, respectively. Renal tissue injury was examined by histological evaluation and renal function was assessed by blood biochemical parameters. Rats treated with vanadate had markedly increased vanadium levels in their plasma, urine, and renal tissues. Vanadate significantly induced renal cAMP and MDA accumulation, whereas the protein level of α1-Na, K-ATPase was suppressed. Vanadate caused renal damage, azotemia, hypokalemia, and hypophosphatemia. Fractional excretions of all studied electrolytes were increased with vanadate administration. These in vivo findings demonstrate that vanadate might suppress renal α1-Na, K-ATPase protein functionally by enhancing cAMP and structurally by augmenting lipid peroxidation.

Rapid Action of Aldosterone on Protein Levels of Sodium-Hydrogen Exchangers and Protein Kinase C Beta Isoforms in Rat Kidney.

Previous in vitro studies demonstrated that aldosterone rapidly activates sodium-hydrogen exchangers 1 and 3 (NHE 1 and 3). In vitro investigations revealed that protein kinase C (PKC) regulates NHE properties. We previously demonstrated that aldosterone rapidly enhances PKCα protein abundance in the rat kidney. There are no reports of renal PKCß (I and II) protein levels related to the regulation by aldosterone. There are also no in vivo data regarding the rapid effects of aldosterone on renal protein levels of NHE (1 and 3) and PKCß (I and II), simultaneously. In the current study, rats received normal saline solution or aldosterone (150 µg/kg BW, i.p.). After 30 minutes, abundance and immunoreactivity of these proteins were determined by Western blot analysis and immunohistochemistry, respectively. Aldosterone increased NHE1 and NHE3 protein abundance to 152% and 134%, respectively (P < 0.05). PKCßI protein level was enhanced by 30%, whereas PKCßII declined slightly. Aldosterone increased NHE protein expression mostly in the medulla. PKCßI immunostaining intensity was increased in the glomeruli, renal vasculature, and thin limb of the loop of Henle, while PKCßII was reduced. This is the first in vivo study to simultaneously demonstrate that aldosterone rapidly elevates PKCßI and NHE (1 and 3) protein abundance in the rat kidney. Aldosterone-induced NHE (1 and 3) protein levels may be related to PKCßI activation.

Rapid nongenomic action of aldosterone on protein expressions of Hsp90( α and ß ) and pc-Src in rat kidney.

Previous in vitro studies indicated that aldosterone nongenomically phosphorylates epidermal growth factor receptor (EGFR) through activation of upstream signals, heat shock protein 90 ß (Hsp90 ß ), and cytosolic (c)-Src kinase. We demonstrated that aldosterone rapidly elevates EGFR phosphorylation in rat kidney. There are no in vivo data regarding renal Hsp90( α and ß ) and phosphorylated (p)c-Src protein expressions. The present study further investigates the expressions of these proteins. Male Wistar rats were intraperitoneally injected with normal saline solution or aldosterone (Aldo: 150 µ g/kg BW). After 30 minutes, abundances and localizations of these proteins were determined. Aldosterone enhanced renal Hsp90 ß protein abundance (P < 0.001), but Hsp90 α and pc-Src protein levels remained unaltered. Expression of Hsp90( α and ß ) was induced prominently in the proximal convoluted tubules (PCTs). Activation of Hsp90 α was observed in vascular and outer medulla regions, whereas Hsp90 ß was induced in the cortex. Immunoreactivity of pc-Src was elevated in PCT with obvious staining at the luminal membrane. This in vivo study is the first to demonstrate that aldosterone nongenomically elevates Hsp90( α and ß ) protein expressions in rat kidney. Aldosterone had no effect on pc-Src protein levels but modulated localization. These results indicate that aldosterone regulates upstream mediators of EGFR transactivation in vivo.

Hibiscus sabdariffa Linnaeus aqueous extracts attenuate the progression of renal injury in 5/6 nephrectomy rats.

Hibiscus sabdariffa Linn. (HS) is a tropical wild plant with antioxidant, antibacterial, antihypertensive, and lipid-lowering properties. In several animal models, HS aqueous extracts reduced the severity of the multi-organ injuries such as hypertension and diabetic nephropathy. One of the multiorgan injuries is chronic kidney disease (CKD), which results from the loss of nephron function. HS was used in a 5/6 nephrectomy (5/6 Nx) rat model to determine if it could attenuate the progression of CKD. HS (250 mg/kg/day) or placebo was orally administered to 5/6 Nx male Sprague-Dawley rats. The Nx+HS group had fewer renal injuries as measured by blood urea nitrogen, serum creatinine, creatinine clearance, and renal pathology when compared with the Nx group. In order to determine which property of HS, either vasodilatory and/or antioxidant, was important in attenuating the progression of CKD, systolic blood pressure (SBP) and serum levels of malondialdehyde (MDA) were assessed. In the Nx+HS group, the SBP and the serum levels of MDA were significantly lower at Week 7. In conclusion, through either antihypertensive and/or antioxidant properties, HS was able to attenuate the progression of renal injury after 5/6 Nx. Hence, HS should be considered as one of the new, promising drugs that can be used to attenuate the progression of CKD.

Nongenomic effects of aldosterone on renal protein expressions of pEGFR and pERK1/2 in rat kidney.

BACKGROUND: In vitro studies have demonstrated that aldosterone elicits nongenomic actions by enhancing protein expressions of phosphorylated epidermal growth factor receptor (pEGFR) and phosphorylated extracellular signal-regulated kinases 1/2 (pERK1/2). There are no available in vivo investigations regarding this action of aldosterone on renal pEGFR-pERK1/2 protein expressions. METHODS: Male Wistar rats received normal saline solution, low-dose (LA: 150 µg/kg BW) or high-dose aldosterone (HA: 500 µg/kg BW) by intraperitoneal injection. After 30 min, protein abundances and localizations of renal pEGFR and pERK1/2 were determined by Western blot and immunohistochemistry. RESULTS: Plasma aldosterone levels were increased in LA and HA groups (p < 0.001). Aldosterone enhanced renal pEGFR and pERK1/2 protein abundances (p < 0.001). HA showed a greater stimulation on pEGFR immunoreactivity than LA in the glomerulus, vasa recta, and thin limb of Henle's loop in the inner medulla area. LA provided more reactivity of pERK1/2 in the thick ascending limb of Henle's loop, outer medullary collecting duct, and proximal straight tubule, whereas HA illustrated more pERK1/2 activation in the glomerulus, peritubular capillary, and inner medulla region. CONCLUSION: This is the first in vivo study which demonstrates that aldosterone, via the nongenomic pathway, could elevate pEGFR and pERK1/2 protein abundances and expressions in the rat kidney. These results indicate that aldosterone induces phosphorylation of EGFR upstream of ERK1/2.

Erythropoietin and its non-erythropoietic derivative: do they ameliorate renal tubulointerstitial injury in ureteral obstruction?

OBJECTIVES: Pleiotropic effects of recombinant human erythropoietin (EPO) have recently been discovered in many non-renal animal models. The renoprotective effects of EPO and carbamylated-erythropoietin (CEPO), a novel EPO which has a small stimulatory effect on hemoglobin, have never been explored in unilateral ureteral obstruction (UUO), a chronic tubulointerstitial (TI) disease model which is independent of systemic factors. METHODS: In order to examine the effects of EPO and CEPO treatments on renal TI injury, 36 male Sprague-Dawley rats, weighing 250-320 g, underwent: UUO without treatment (group 1, n = 12), UUO with EPO (groups 2, n = 12), and UUO with CEPO (group 3, n = 12). EPO and CEPO were injected subcutaneously at a dose of 5000 u/kg to each respective rat at 1 day pre-UUO and at day 3, 7 and 10 post-UUO. After days 3, 7, and 14 of UUO, TI injury, collagen, alpha-smooth muscle actin (alpha-SMA) positive cell, ED1-positive cell, terminal deoxynucleotidyl transferase (TdT) mediated nick-end labeling (TUNEL)-positive cell, and transforming growth factor-beta1 (TGF-beta1) messenger ribonucleic acid (mRNA) were determined. Bcl-2 expression was also assessed to verify the mechanism of apoptosis. RESULTS: At day 14 UUO caused severe TI injury with a significant increase in collagen, alpha-SMA, ED1-positive cell, TUNEL-positive cell, and TGF-beta1 mRNA expression. Administration of EPO and CEPO significantly attenuated TI injury, collagen, ED1-positive cells, and TUNEL-positive cells. Only CEPO-treated rats had decreased alpha-SMA positive cells and TGF-beta1 mRNA. The expression of Bcl-2 was demonstrated only in EPO-treated rats. The hematocrit levels in EPO-treated rats were higher than the control and CEPO-treated rats. CONCLUSIONS: EPO and CEPO can limit 14-day UUO-induced TI injury by reducing inflammation, interstitial fibrosis, and tubular apoptosis.

Role of angiotensin II on dihydrofolate reductase, GTP-cyclohydrolase 1 and nitric oxide synthase expressions in renal ischemia-reperfusion.

BACKGROUND: The present study was conducted to investigate the role of renal ischemia-reperfusion (IR) and angiotensin II (ANG II) on mRNA and protein levels of renal dihydrofolate reductase (DHFR), GTP-cyclohydrolase 1 (GTP- CH 1), and endothelial and inducible nitric oxide synthase (eNOS and iNOS, respectively). METHODS: Male Wistar rats were sham operated or received IR (30 min occlusion, and reperfusion for 1 day). Each group was treated separately with water, angiotensin-converting enzyme inhibitor (ACEI) and ANG II receptor type 1 blocker (ARB) for 1 day before the sham operation or IR, and continuously for 1 day after the operation. The mRNA and protein levels were detected by RT-PCR and Western blot, respectively. RESULTS: IR decreased DHFR mRNA and protein levels (p < 0.01), both of which were restored by ACEI or ARB, whereas GTP-CH 1 expression was unaltered. IR suppressed eNOS dimer while enhancing the monomer (p < 0.01). IR augmented iNOS mRNA, total iNOS protein and iNOS monomer (all p < 0.01) which were attenuated by ACEI or ARB. CONCLUSION: Our study is the first to demonstrate that the heightened ANG II in IR, via stimulation of ANG II receptor type 1, suppresses DHFR and eNOS dimer, while activating both iNOS mRNA and protein levels.

Nutritional effect of nandrolone decanoate in predialysis patients with chronic kidney disease.

OBJECTIVE: The study objective was to examine the nutritional effect of nandrolone decanoate, an androgen derivative, in predialysis patients with chronic kidney disease (CKD). DESIGN: This was a prospective and experimental study. SETTING: The study was performed at the institutional level of clinical care. PATIENTS: Twenty-nine predialysis patients with CKD, with a glomerular filtration rate between 5 and 30 mL/min and moderate to severe malnutrition, were included and randomly divided into control (n = 13) and nandrolone decanoate (NAN, n = 16) groups. INTERVENTION: Patients in the control group received optimally conventional treatment of CKD. Patients in the NAN group, in addition to the conventional treatment, were intramuscularly injected with nandrolone decanoate at the dose of 100 mg per for 3 months. MAIN OUTCOME MEASURE: Nutritional markers, including lean body mass (LBM), normalized protein catabolic rate, serum albumin, and lipids, were determined at baseline and 3-month periods. RESULTS: Baseline parameters in both groups were not different. After 3 months, the patients in the NAN group had increased LBM (P < .01) and decreased serum albumin levels (P < .05), but no changes in the values of normalized protein catabolic rate, serum lipids, hematocrit, and glomerular filtration rate. No alterations in all parameters were identified in the control group. Changes in LBM in the NAN group were significantly higher than in the control group (P < .05). Minor adverse effects were observed in a few patients in the NAN group. CONCLUSION: Nandrolone decanoate expresses an anabolic effect on LBM without altering the renal function and thus would provide nutritional benefit in predialysis patients with CKD.

Lipid peroxidation and renal injury in renal ischemic reperfusion: effect ofangiotensin inhibition.

OBJECTIVES: To investigate the role of angiotensin inhibition on lipid peroxidation (LPO) and renal pathology in ischemic reperfusion (IR). MATERIAL AND METHOD: Male Wistar rats were subjected to 15-, 30-, 45- or 60- minutes ofrenal ischemia (I) by left renal artery occlusion. In the 30-minute I group, reperfusion (R) for I day (13,R) was performed in additional animals that had been treated with water, angiotensin converting enzyme inhibitor (ACE]; enalapril 5 mg/kg/d), or angiotensin receptor type 1 blocker (ARB; losartan 10 mg/kg/d) one day before I and were continued for 1 day after R. Renal tissue malondialdehyde (MDA), an indicator of LPO, was examined during I and IR periods. Renal pathology was also determined. RESULTS: During ischemia, renal tissue MDA levels were increased throughout the 60-minute ischemic period and was maximum at 30 minutes of ischemia (p < 0.01). Histological changes in 30-minutes I group showed slight tubular cell congestion and mild interstitial edema. One day after reperfusion, MDA levels were still elevated (p < 0. 01) when compared with sham. Progression of renal pathology was observed after I day of reperfusion. Both ACEI and ARB could attenuate the heightened MDA levels (p < 0.01). IR-induced renal injury was markedly diminished by administration ofACEI as well as by ARB. CONCLUSION: These results indicate that inhibition of angiotensin could reduce lipid peroxidation and ameliorate renal injury during IR condition.

Citrate attenuates tubulointerstitial fibrosis in 5/6 nephrectomized rats by decreasing transforming growth factor-beta1.

OBJECTIVE: Tubulointerstitial fibrosis plays an essential role in progression to end stage renal disease (ESRD) in various chronic renal failure (CRF) models including the 5/6 nephrectomy (5/6). The present study examines the renoprotective effect of citrate in the renal ablative model that is quite similar to CRF in human. MATERIAL AND METHOD: Male Wistar rats underwent 5/6 and were fed with tap water (5/6tap) or tap water containing 67 mEq/L citrate solution (5/6cit). Sham-operated rats (S) were divided into Stap and Scit groups. Renal function, renal histopathology, renal alpha-Smooth muscle actin (SMA), and renal transforming growth factor (TGF)-beta1 were determined immediately and at the 8th week after operation. RESULTS: Following the surgery, the values of glomerular filtration rate (GFR) in the 5/6tap and the 5/6cit groups were 2.39 +/- 0.25 and 2.35 +/- 0.25 (mL/kg/min), respectively, both were significantly lower than sham groups (p < 0.05). At the eighth week, the 5/6tap group had progressively decreased GFR and had higher fibrosis score, increased alpha-SMA positive cells, and renal tissue TGF- beta1 when compared with the sham groups. The 5/ 6cit group, when compared with the 5/6tap group, had higher GFR (2.51 +/- 0.22 vs 1.17 +/- 0.33 mL/kg/min; p < 0.05), lower fibrosis score (1.83 +/- 0.88 vs 3.0 +/- 0.4, p < 0.001), lower alpha-SMA activity (159 +/- 2.9 vs 187 +/- 12.3 cells per 1000 interstitial cells, p < 0.05), and lower renal TGF-beta1 levels (1771.3 +/- 239.5 vs 4716.9 +/- 871.2 pg/mg protein, p < 0.005). CONCLUSION: As such, in 5/6 nephrectomized rats, citrate therapy for eight weeks could decrease tubulointerstitial fibrosis mainly by reducing the heightened renal TGF-beta1 levels and additionally by attenuating the increased myofibroblast activity.

Apoptosis of circulating lymphocyte in rats with unilateral ureteral obstruction: role of angiotensin II.

BACKGROUND: Unilateral ureteral obstruction (UUO) could induce increased renal angiotensin II (ANG II), which enhances apoptosis of renal tubular cells and renal tissue loss. Systemic ANG II is also increased in UUO. There are no data available about whether UUO can induce apoptosis of circulating lymphocytes or not. METHODS: UUO or sham-operated male Wistar rats (n = 8 in each group) were fed a drinking solution containing water, angiotensin II receptor type 1 antagonist (ARA; losartan, 500 mg/L) or angiotensin-converting enzyme inhibitor (ACEI; enalapril: 200 mg/L) for 1 day or 7 days. Blood samples were collected and circulating lymphocyte cells were separated. The apoptotic cells were detected by in situ terminal deoxynucleotidyl transferase (TdT assay)-mediated digoxigenin/antidigoxigenin conjugated fluorescein method and counted under a fluorescence microscope. The apoptotic index was calculated. RESULTS: UUO caused marked increases in the apoptotic index of circulating lymphocytes in UUO rats at both 1 day and 7 days when compared with the respective sham groups (P < 0.001). Neither ARA nor ACEI treatment had an effect on the apoptotic index values in the UUO rats at 1 day. In the UUO rats at 7 days, the apoptosis of circulating lymphocytes was markedly decreased from 29.2 +/- 2.7% to 11.9 +/- 2.7% (P < 0.01) in the ARA-treated rats and to 7.6 +/- 2.7% (P < 0.001) in the ACEI-treated rats. CONCLUSION: UUO, via stimulation of ANG II, could promptly enhance apoptosis of circulating lymphocytes. The apoptosis persisted throughout the 7 days of the study. Prolonged UUO would impair lymphocyte cell immunity and the host defense mechanism. Continuous treatment with either ARA or ACEI could abrogate ANG II-stimulated circulating lymphocyte apoptosis.

Acute hypercalcemia-induced hypertension: the roles of calcium channel and alpha-1 adrenergic receptor.

OBJECTIVE: To study the mechanism(s) of acute hypercalcemia-induced hypertension in dogs. MATERIAL AND METHOD: Adult male mongrel dogs were intravenously infused with: 1) normal saline solution, 2) CaCl2 solution, 3) CaCl2 + calcium channel blocker (verapamil), 4) CaCl2 + selective alpha-1 adrenergic receptor blocker (prazosin), or 5) CaCl2 + verapamil + prazosin. Either verapamil or prazosin treatment was started at forty minutes before CaCl2 infusion and then was co-administered throughout the three-hour experimental period. Systemic and renal hemodynamics parameters were determined. RESULTS: Infusion of CaCl2 caused increases in mean arterial blood pressure (p < 0.01), total peripheral resistance (p < 0.001), and renal vascular resistance (p < 0.001). Prior treatment with either verapamil or prazosin lowered baseline blood pressure (p < 0.01) and could prevent hypercalcemia-induced hypertension. This occurred accompanying regaining to near normal values of abnormal systemic hemodynamics parameters. Combination of both drugs showed more profound effects, particularly on lowering renal vascular resistance. CONCLUSION: Acute hypercalemic hypertension is caused by an increase in vascular resistance mediated via the direct effect of calcium on vascular smooth muscle as well as the indirect effect of calcium induced hypercatecholaminemia. The stimulatory effect of hypercalcemia on renal vascular resistance is more prominent than that on peripheral vascular resistance.