Hemodynamic and Hormonal Effects of Tolvaptan for Heart Failure

Tolvaptan (TLV) is a diuretic agent administrated for heart failure (HF) only in Japan. Many clinical findings have been obtained from the accumulation of clinical experience, and the administration of TLV reportedly avoids causing a reduction in the renal function. In addition, TLV has been reported to exert effects other than diuresis. The early start of TLV after hospitalization shortens the length of the hospital stay, and continuous TLV after discharge extends the period until re-hospitalization of HF patients. TLV is thought to function via vasopressin V2 receptor antagonism. However, no significant differences in the long-term prognosis were noted between the group using TLV and not using TLV in the Endovascular Valve Edge-to-Edge Repair Study (EVEREST) trial, and effects other than diuresis are not useful for all HF patients. Therefore, it is necessary to identify patients who may experience effects other than diuresis with TLV administration. The accumulation of more patients and findings from further large-scale clinical trials will be necessary in order to clarify these points.

Diuretic, Natriuretic, and Vasodepressor Activity of a Lipid Fraction Enhanced in Medium of Cultured Mouse Medullary Interstitial Cells by a Selective Fatty Acid Amide Hydrolase Inhibitor

The relationship between the endocannabinoid system in the renal medulla and the long-term regulation of blood pressure is not yet understood. To investigate the possible role of the endocannabinoid system in renomedullary interstitial cells, mouse medullary interstitial cells (MMICs) were obtained, cultured, and characterized for their responses to treatment with a selective inhibitor of fatty acid amide hydrolase, PF-3845 (N-3-pyridinyl-4-[[3-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenyl]methyl]-1-piperidinecarboxamide). Treatment of MMICs with PF-3845 increased cytoplasmic lipid granules detected by Sudan Black B staining and multilamellar bodies identified by transmission electron microscopy. High-performance liquid chromatography (HPLC) analyses of lipid extracts of MMIC culture medium revealed a 205-nm absorbing peak that showed responsiveness to PF-3845 treatment. The biologic activities of the PF-3845-induced product (PIP) isolated by HPLC were investigated in anesthetized, normotensive surgically instrumented mice. Intramedullary and intravenous infusion of PIP at low dose rates (0.5-1 area units under the peak/10 min) stimulated diuresis and natriuresis, whereas these parameters returned toward baseline at higher doses but mean arterial pressure (MAP) was lowered. Whereas intravenous bolus doses of PIP stimulated diuresis, the glomerular filtration rate, and medullary blood flow (MBF) and reduced or had no effect on MAP, an intraperitoneal bolus injection of PIP reduced MAP, increased MBF, and had no effect on urine parameters. These data support a model whereby PF-3845 treatment of MMICs results in increased secretion of a neutral lipid that acts directly to promote diuresis and natriuresis and indirectly through metabolites to produce vasodepression. Efforts to identify the structure of the PF-3845-induced lipid and its relationship to the previously proposed renomedullary antihypertensive lipids are ongoing.

Slc4a8 in the Kidney: Expression, Subcellular Localization and Role in Salt Reabsorption

BACKGROUND/AIMS

The sodium-dependent bicarbonate transporter Slc4a8 (a.k.a NDCBE) mediates the co-transport of sodium and bicarbonate in exchange for chloride. It is abundantly detected in the brain, with low expression levels in the kidney. The cell distribution and subcellular localization of Slc4a8 in the kidney and its role in acid/base and electrolyte homeostasis has been the subject of conflicting reports. There are no conclusive localization or functional studies to pinpoint the location and demonstrate the function of Slc4a8 in the kidney.

METHODS

Molecular techniques, including RT-PCR and in situ hybridization, were performed on kidney sections and tagged epitopes were used to examine the membrane targeting of Slc4a8 in polarized kidney cells. Crispr/Cas9 was used to generate and examine Slc4a8 KO mice.

RESULTS

Zonal distribution and in situ hybridization studies showed very little expression for Slc4a8 (NDCBE) in the cortex or in cortical collecting ducts (CCD). Slc4a8 was predominantly detected in the outer and inner medullary collecting ducts (OMCD and IMCD), and was targeted to the basolateral membrane of osmotically tolerant MDCK cells. Slc4a8 KO mice did not show any abnormal salt or bicarbonate wasting under baseline conditions or in response to bicarbonate loading, salt restriction or furosemide-induced diuresis.

CONCLUSION

Slc4a8 (NDCBE) is absent in the CCD and is predominantly localized on the basolateral membrane of medullary collecting duct cells. Further, Slc4a8 deletion does not cause significant acid base or electrolyte abnormalities in pathophysiologic states. Additional studies are needed to examine the role of Slc4a8 (NDCBE) in intracellular pH and volume regulation in medullary collecting duct cells.

Unmasking a sustained negative effect of SGLT2 inhibition on body fluid volume in the rat

The chronic intrinsic diuretic and natriuretic tone of sodium-glucose cotransporter 2 (SGLT2) inhibitors is incompletely understood because their effect on body fluid volume (BFV) has not been fully evaluated and because they often increase food and fluid intake at the same time. Here we first compared the effect of the SGLT2 inhibitor ipragliflozin (Ipra, 0.01% in diet for 8 wk) and vehicle (Veh) in Spontaneously Diabetic Torii rat, a nonobese type 2 diabetic model, and nondiabetic Sprague-Dawley rats. In nondiabetic rats, Ipra increased urinary excretion of Na+ (UNaV) and fluid (UV) associated with increased food and fluid intake. Diabetes increased these four parameters, but Ipra had no further effect, probably because of its antihyperglycemic effect, such that glucosuria and, as a consequence, food and fluid intake were unchanged. Fluid balance and BFV, determined by bioimpedance spectroscopy, were similar among the four groups. To study the impact of food and fluid intake, nondiabetic rats were treated for 7 days with Veh, Ipra, or Ipra+pair feeding+pair drinking (Pair-Ipra). Pair-Ipra maintained a small increase in UV and UNaV versus Veh despite similar food and fluid intake. Pair-Ipra induced a negative fluid balance and decreased BFV, whereas Ipra or Veh had no significant effect compared with basal values. In conclusion, SGLT2 inhibition induces a sustained diuretic and natriuretic tone. Homeostatic mechanisms are activated to stabilize BFV, including compensatory increases in fluid and food intake.

The design and rationale for the Dapagliflozin Effect on Cardiovascular Events (DECLARE)-TIMI 58 Trial

BACKGROUND

Dapagliflozin is a sodium-glucose co-transporter-2 (SGLT-2) inhibitor that reduces blood glucose in patients with type 2 diabetes mellitus (T2DM) by promoting glycosuria via inhibiting urinary glucose reabsorption. In addition to improving blood glucose control, treatment with dapagliflozin results in glucose-induced osmotic diuresis, weight loss, and blood pressure lowering. Previous trials of SGLT-2 inhibitors showed reductions in cardiovascular (CV) events, including CV death and hospitalization for heart failure, and ischemic events in patients with atherosclerotic cardiovascular disease (ASCVD).

RESEARCH DESIGN AND METHODS

DECLARE-TIMI 58 (NCT01730534) is a phase 3b randomized, double-blind, placebo-controlled trial designed to evaluate the CV safety and efficacy of dapagliflozin that has completed randomization of 17,160 patients with T2DM and a history of either established ASCVD (n=6,971) or multiple risk factors for ASCVD (n=10,189). Patients were randomized in a 1:1 fashion to dapagliflozin 10 mg or matching placebo. The primary safety outcome is the time to the first event of the composite of CV death, myocardial infarction, or ischemic stroke (major adverse cardiovascular events; MACEs). The co-primary efficacy outcomes are the composite of CV death, myocardial infarction, or ischemic stroke and the composite of CV death or hospitalization for heart failure. This event-driven trial will continue until at least 1,390 subjects have a MACE outcome, thereby providing >99% power to test for the primary outcome of safety of dapagliflozin measured by rejecting the hypothesis that the upper bound of the CI >1.3 for the primary outcome of MACE, as well as 85% power to detect a 15% relative risk reduction in MACE and an estimated 87% power to detect a 20% reduction in the composite of CV death or hospitalization for heart failure at a 1-sided α level of .0231.

CONCLUSION

The DECLARE-TIMI 58 trial is testing the hypotheses that dapagliflozin is safe (does not increase) and may reduce the occurrence of major CV events. DECLARE-TIMI 58 is the largest study to address this question with an SGLT-2 inhibitor in patients with T2DM and with established CV disease and without CV disease but with multiple risk factors.

Worsening Renal Function in Patients With Acute Heart Failure Undergoing Aggressive Diuresis Is Not Associated With Tubular Injury

BACKGROUND

Worsening renal function (WRF) in the setting of aggressive diuresis for acute heart failure treatment may reflect renal tubular injury or simply indicate a hemodynamic or functional change in glomerular filtration. Well-validated tubular injury biomarkers, N-acetyl-β-d-glucosaminidase, neutrophil gelatinase-associated lipocalin, and kidney injury molecule 1, are now available that can quantify the degree of renal tubular injury. The ROSE-AHF trial (Renal Optimization Strategies Evaluation-Acute Heart Failure) provides an experimental platform for the study of mechanisms of WRF during aggressive diuresis for acute heart failure because the ROSE-AHF protocol dictated high-dose loop diuretic therapy in all patients. We sought to determine whether tubular injury biomarkers are associated with WRF in the setting of aggressive diuresis and its association with prognosis.

METHODS

Patients in the multicenter ROSE-AHF trial with baseline and 72-hour urine tubular injury biomarkers were analyzed (n=283). WRF was defined as a ≥20% decrease in glomerular filtration rate estimated with cystatin C.

RESULTS

Consistent with protocol-driven aggressive dosing of loop diuretics, participants received a median 560 mg IV furosemide equivalents (interquartile range, 300-815 mg), which induced a urine output of 8425 mL (interquartile range, 6341-10 528 mL) over the 72-hour intervention period. Levels of N-acetyl-β-d-glucosaminidase and kidney injury molecule 1 did not change with aggressive diuresis (both P>0.59), whereas levels of neutrophil gelatinase-associated lipocalin decreased slightly (-8.7 ng/mg; interquartile range, -169 to 35 ng/mg; P<0.001). WRF occurred in 21.2% of the population and was not associated with an increase in any marker of renal tubular injury: neutrophil gelatinase-associated lipocalin (P=0.21), N-acetyl-β-d-glucosaminidase (P=0.46), or kidney injury molecule 1 (P=0.22). Increases in neutrophil gelatinase-associated lipocalin, N-acetyl-β-d-glucosaminidase, and kidney injury molecule 1 were paradoxically associated with improved survival (adjusted hazard ratio, 0.80 per 10 percentile increase; 95% confidence interval, 0.69-0.91; P=0.001).

CONCLUSIONS

Kidney tubular injury does not appear to have an association with WRF in the context of aggressive diuresis of patients with acute heart failure. These findings reinforce the notion that the small to moderate deteriorations in renal function commonly encountered with aggressive diuresis are dissimilar from traditional causes of acute kidney injury.

SGLT2 inhibition in a kidney with reduced nephron number: modeling and analysis of solute transport and metabolism

Sodium-glucose cotransporter 2 (SGLT2) inhibitors enhance urinary glucose, Na+ and fluid excretion, and lower hyperglycemia in diabetes by targeting Na+ and glucose reabsorption along the proximal convoluted tubule. A goal of this study was to predict the effects of SGLT2 inhibitors in diabetic and nondiabetic patients with chronic kidney disease. To that end, we employed computational rat kidney models to explore how SGLT2 inhibition affects renal solute transport and metabolism when nephron populations are normal or reduced. Model simulations suggested that in a nondiabetic rat, acute and chronic SGLT2 inhibition induces glucosuria, diuresis, natriuresis, and kaliuresis. Those effects were stronger with chronic SGLT2 inhibition (due to SGLT1 downregulation) and tempered by nephron loss. In a diabetic rat with normal nephron number, acute SGLT2 inhibition similarly elevated urine fluid, Na+, and K+ excretion, whereas the urinary excretory effects of chronic SGLT2 inhibition were attenuated in proportion to its plasma glucose level lowering effect. Nephron loss in a diabetic kidney was predicted to lower the glucosuric and blood glucose-reducing effect of chronic SGLT2 inhibition, but due to the high luminal glucose delivery in the remaining hyperfiltering nephrons, nephron loss enhanced proximal tubular paracellular Na+ secretion, thereby augmenting the natriuretic, diuretic, and kaliuretic effects. A proposed shift in oxygen-consuming active transport to the outer medulla, which may simulate systemic hypoxia and enhance erythropoiesis, was also preserved with nephron loss. These effects may contribute to the protective effects of SGLT2 inhibitors on blood pressure and heart failure observed in diabetic patients with chronic kidney diseases.

Nanomolar-Potency 1,2,4-Triazoloquinoxaline Inhibitors of the Kidney Urea Transporter UT-A1

Urea transporter A (UT-A) isoforms encoded by the Slc14a2 gene are expressed in kidney tubule epithelial cells, where they facilitate urinary concentration. UT-A1 inhibition is predicted to produce a unique salt-sparing diuretic action in edema and hyponatremia. Here we report the discovery of 1,2,4-triazoloquinoxalines and the analysis of 37 synthesized analogues. The most potent compound, 8ay, containing 1,2,4-triazolo[4,3- a]quinoxaline-substituted benzenesulfonamide linked by an aryl ether, rapidly and reversibly inhibited UT-A1 urea transport by a noncompetitive mechanism with IC50 ≈ 150 nM; the IC50 was ∼2 μM for the related urea transporter UT-B encoded by the Slc14a1 gene. Molecular modeling suggested a putative binding site on the UT-A1 cytoplasmic domain. In vitro metabolism showing quinoxaline ring oxidation prompted the synthesis of metabolically stable 7,8-difluoroquinoxaline analogue 8bl, which when administered to rats produced marked diuresis and reduced urinary osmolality. 8bl has substantially improved UT-A1 inhibition potency and metabolic stability compared with prior compounds.

Why do SGLT2 inhibitors reduce heart failure hospitalization? A differential volume regulation hypothesis

The effect of a sodium glucose cotransporter 2 inhibitor (SGLT2i) in reducing heart failure hospitalization in the EMPA-REG OUTCOMES trial has raised the possibility of using these agents to treat established heart failure. We hypothesize that osmotic diuresis induced by SGLT2 inhibition, a distinctly different diuretic mechanism than that of other diuretic classes, results in greater electrolyte-free water clearance and, ultimately, in greater fluid clearance from the interstitial fluid (IF) space than from the circulation, potentially resulting in congestion relief with minimal impact on blood volume, arterial filling and organ perfusion. We utilize a mathematical model to illustrate that electrolyte-free water clearance results in a greater reduction in IF volume compared to blood volume, and that this difference may be mediated by peripheral sequestration of osmotically inactive sodium. By coupling the model with data on plasma and urinary sodium and water in healthy subjects who received either the SGLT2i dapagliflozin or loop diuretic bumetanide, we predict that dapagliflozin produces a 2-fold greater reduction in IF volume compared to blood volume, while the reduction in IF volume with bumetanide is only 78% of the reduction in blood volume. Heart failure is characterized by excess fluid accumulation, in both the vascular compartment and interstitial space, yet many heart failure patients have arterial underfilling because of low cardiac output, which may be aggravated by conventional diuretic treatment. Thus, we hypothesize that, by reducing IF volume to a greater extent than blood volume, SGLT2 inhibitors might provide better control of congestion without reducing arterial filling and perfusion.

[NefroCAPS phytolysin in complex management of women with chronic recurrent cystitis]

RELEVANCE

Recurrent lower urinary tract infections (UTI) in women are one of the most challenging problems of modern urology, which is associated both with their high incidence and increasing resistance of uropathogens to antibacterial drugs. Due to this fact, the phytotherapy of infectious and inflammatory diseases of the urinary tract has received increased attention.

AIM

To investigate the effectiveness of Phytolysin nefroCAPS in the complex management of women with chronic recurrent cystitis.

MATERIALS AND METHODS

50 women with chronic recurrent cystitis underwent a complex examination. They were divided into two groups depending on the treatment they received. Patients of the 1st group (n=27) received a combination therapy: fosfomycin (monural) 3 g (single dose) and Phytolysin nefroCAPS one capsule three times daily for three months. Patients of the 2nd group (n=23) were administered a single 3-g dose of fosfomycin (monural).

RESULTS

Follow-up examinations were performed 1, 3 and six months after initiation of the treatment. In patients of the 1st group, clinical manifestations of the disease disappeared earlier, and they had fewer recurrences than the patients of the 2nd group. Also, bacteriological study of urine showed a more persistent antimicrobial effect among patients of the 1st group.

CONCLUSION

In patients with chronic recurrent cystitis, plant-based preparation Phytolysin nefroCAPS administered concurrently with an antibacterial drug is more effective than antibiotic monotherapy.

[The influence of peptides on the morphofunctional state of old rats kidneys.]

More than a quarter of the elderly and senile age population suffers from kidney pathology. For this reason, a prophylaxis of kidney diseases with the safe and effective nephroprotectors is a priority of gerontology. An influence of polypeptide kidney complex (PKC), peptides AED, EDL, AEDG on the functional state of old rats kidneys was studied in research. Administration of PKC, peptides AED and EDL increased diuresis by 1,2-1,4 times. PKC and peptide AED reduced urine protein level and protein excretion by 1,5-2,8 times. PKC, peptides AED and EDL increased distal sodium transport by 1,2-1,3 times. Peptides AED and EDL increased sodium excretion by 1,3 and 1,6 times, respectively. Renal effects of peptide AEDG resulted in a reduction of glomerular filtration rate by 21%, decrease in urine protein level by 3,1 times and protein excretion - by 2,5 times. Peptide AEDG reduced absolute sodium reabsorption by 1,3 times and increased distal sodium transport by 1,4 times. Realization of glomerular-tubular and tubular-tubular balances is verified by correlation between glomerular filtration rate (GFR) and absolute sodium reabsorption, proximal and distal sodium reabsorption. In kidney tissue a stimulation of the antioxidant enzymes activity on the background of inhibition of the peroxidation processes intensity was observed, which in complex with morphological data evidences the absence of nephrotoxic effects. PKC, peptides AED, EDL and AEDG may be considered as nephroprotective agents in kidney aging.

[Neprilysin inhibition and chronic kidney disease]

Patients with chronic kidney disease (CKD) have a higher incidence of cardiovascular (acute and chronic) events, which in turn have an increased risk of progression to end-stage renal disease (ESRD) Inhibition of neprilysin, in addition to offering a new therapeutic target in patients with heart failure, could represent a potential improvement strategy in cardiovascular and renal outcome of patients with CKD. Inhibition of neprilysin by inhibiting the breakdown of natriuretic peptides, increases their bioavailability resulting in an increase in diuresis and sodium excretion and, in addition to exerting an inhibition of the renin-angiotensin-aldosterone (RAAS) system. Inhibition of RAAS, in turn, generates a series of counter-regulations that can balance the adverse effects present in CKD and heart failure (HF). The idea of blocking neprilysin is not very recent, but the first drugs used as inhibitors had an inadmissible incidence of angioedema. Among the latest generation molecules that can perform a specific inhibitory action on the neprilysin receptor and, at the same time, on the angiotensin II receptor thanks to the association with valsartan there is the LCZ696 (sacubitril / valsartan). This drug has shown promising benefits both in the treatment arterial hypertension and heart failure. It is hoped that equally positive effects may occur in CKD patients, particularly those with macroproteinuria.

Ablation of the Cl-/HCO3- Exchanger Pendrin Enhances Hydrochlorothiazide-Induced Diuresis

BACKGROUND/AIMS

The Cl-/HCO3- exchanger pendrin and the thiazide-sensitive Na-Cl cotransporter NCC are expressed in the kidney distal nephron and mediate salt absorption. We hypothesized that deletion of pendrin leaves NCC as the major salt absorbing transporter in the distal nephron and therefore enhances salt excretion by hydrochlorothiazide (HCTZ).

METHODS

Metabolic cage studies were performed in wild type, pendrin KO and NCC KO mice at baseline and following HCTZ treatment. In parallel studies, systemic blood pressure was measured in mice treated with HCTZ with the tail cuff method.

RESULTS

Urine output, salt excretion and water intake were comparable in all groups under baseline condition. Urine output and water intake increased significantly only in pendrin KO mice in response to HCTZ, but not in WT or NCC KO mice. Sodium and chloride excretion increased in HCTZ-treated pendrin KO mice, but they remained unchanged in WT or NCC KO mice. Pendrin KO mice treated with HCTZ developed volume depletion, as determined by increased expression of renin mRNA and protein. The expression of ENaC and pendrin increased in HCTZ-treated WT mice. HCTZ treatment did not significantly modify blood pressure in any of the experimental group.

CONCLUSION

The ablation of the Cl-/HCO3- exchanger Pendrin enhances the magnitude of salt wasting by HCTZ.

First-in-Man Demonstration of Direct Endothelin-Mediated Natriuresis and Diuresis

Endothelin (ET) receptor antagonists are potentially novel therapeutic agents in chronic kidney disease and resistant hypertension, but their use is complicated by sodium and water retention. In animal studies, this side effect arises from ETB receptor blockade in the renal tubule. Previous attempts to determine whether this mechanism operates in humans have been confounded by the hemodynamic consequences of ET receptor stimulation/blockade. We aimed to determine the effects of ET signaling on salt transport in the human nephron by administering subpressor doses of the ET-1 precursor, big ET-1. We conducted a 2-phase randomized, double-blind, placebo-controlled crossover study in 10 healthy volunteers. After sodium restriction, subjects received either intravenous placebo or big ET-1, in escalating dose (≤300 pmol/min). This increased plasma concentration and urinary excretion of ET-1. Big ET-1 reduced heart rate (≈8 beats/min) but did not otherwise affect systemic hemodynamics or glomerular filtration rate. Big ET-1 increased the fractional excretion of sodium (from 0.5 to 1.0%). It also increased free water clearance and tended to increase the abundance of the sodium-potassium-chloride cotransporter (NKCC2) in urinary extracellular vesicles. Our protocol induced modest increases in circulating and urinary ET-1. Sodium and water excretion increased in the absence of significant hemodynamic perturbation, supporting a direct action of ET-1 on the renal tubule. Our data also suggest that sodium reabsorption is stimulated by ET-1 in the thick ascending limb and suppressed in the distal renal tubule. Fluid retention associated with ET receptor antagonist therapy may be circumvented by coprescribing potassium-sparing diuretics.

Early treatment with tolvaptan improves diuretic response in acute heart failure with renal dysfunction

BACKGROUND

Poor response to diuretics is associated with worse prognosis in patients with acute heart failure (AHF). We hypothesized that treatment with tolvaptan improves diuretic response in patients with AHF.

METHODS

We performed a secondary analysis of the AQUAMARINE open-label randomized study in which a total of 217 AHF patients with renal impairment (eGFR < 60 mL/min/1.73 m²) were randomized to either tolvaptan or conventional treatment. We evaluated diuretic response to 40 mg furosemide or its equivalent based on two different parameters: change in body weight and net fluid loss within 48 h.

RESULTS

The mean time from patient presentation to randomization was 2.9 h. Patients with a better diuretic response showed greater relief of dyspnea and less worsening of renal function. Tolvaptan patients showed a significantly better diuretic response measured by diuretic response based both body weight [-1.16 (IQR -3.00 to -0.57) kg/40 mg vs. -0.51 (IQR -1.13 to -0.20) kg/40 mg; P < 0.001] and net fluid loss [2125.0 (IQR 1370.0-3856.3) mL/40 mg vs. 1296.3 (IQR 725.2-1726.5) mL/40 mg; P < 0.001]. Higher diastolic blood pressure and use of tolvaptan were independent predictors of a better diuretic response.

CONCLUSIONS

Better diuretic response was associated with greater dyspnea relief and less WRF. Early treatment with tolvaptan significantly improved diuretic response in AHF patients with renal dysfunction.

Bolus Injection Versus Infusion of Furosemide in Kidney Transplantation: A Randomized Clinical Trial

PURPOSE

Furosemide is commonly administered to increase the urinary output in patients with transplanted kidneys. This study compared the two administration routes of furosemide (bolus versus infusion) in kidney transplanted patients.

MATERIALS AND METHODS

Fifty patients who had undergone kidney transplantation in 2015 in a hospital in Tabriz, Iran, were included in this clinical trial. They were divided into two groups: bolus (120 mg stat) and infusion (4 mg/minute) groups. The primary outcome was urine onset time. Secondary outcomes were urine output volume, vital signs (blood pressure, heart rate), and electrolyte level (creatinine, blood urea nitrogen, sodium and potassium). After arterial and venous anastomoses, arterial clamp removal time and diuresis onset were recorded. Finally, theurinary output volumes of both groups were measured with regular urine bags for an hour after anastomosis. Then it was repeated each three hours for 24 hours, and eventually two and three days thereafter. Finally, all data were statistically analyzed.

RESULTS

Around 72% of the patients were men (mean age of 37.15 &plusmn; 14.67 years). Urine output was higher in bolus group but it was not statistically significant. Diuresis duration was measured after arterial declamping and its averages were 5.41 &plusmn; 3.7 minutes and 9.36 &plusmn; 7.65 minutes in bolus and infusion groups, respectively (P = .040). Furosemide bolus injection and infusion had no significant effect on creatinine, blood urea nitrogen, sodium and potassium.

CONCLUSION

Furosemide bolus injection can reduce diuresis onset time compared to furosemide infusion.

COMPARISON OF THE EFFECTS OF MARSANIDINE DERIVATIVES ON RAT CARDIOVASCULAR SYSTEM

Since clonidine was introduced in clinical practice, attempts are still made to obtain substances capable of centrally controlling blood pressure, however with pharmacological profile better than currently avail- able, such as moxonidine and rilmenidine. Recently synthesized indazole derivatives exert promising action on blood pressure and heart rate in Wistar rats. In the present study, our aim was to check which of tested substituted compound exerts the best effect on basic circulatory parameters. Effects of marsanidine (M), 7-Me- marsanidine (7-Me-M), 7-Cl-marsanidine (7-Cl-M) and 7-F-marsanidine (7-F-M) on blood pressure, heart rate and diuresis were compared. Male Wistar rats were receiving iv. tested compounds in two doses: 10 or 100 pg/kg b.w. Mean arterial pressure (MAP), heart rate (HR) and ECG were recorded continuously. Urine samples were collected before and after administration of tested imidazolines. Obtained data were filtered and subjected to statistical analysis. All tested compounds caused a profound decrease of MAP. 7-M-M reduced blood pressure to the highest extent when used in 10 μg/kg b.w. dose. 7-F-M in dose of 100 μg/kg b.w. caused the strongest drop of MAP. The weakest and the shortest effect in duration was observed after M administration. HR was reduced after administration of each compound while the strongest effect was observed after 7-M-M administration in dose of 10 μg/kg b.w. and after 7-Cl-M administered in dose of 100 μg/kg b.w. Again, the weakest and the shortest in duration effect was observed after M administration. The highest increase of diuresis was observed after 7-M-M administration. These data suggest that methyl substituent in 7 position of indazole ring is the most effective in improving hypotensive effects of newly synthesized imidazolidine derivatives.

Overlap of Post-obstructive Diuresis and Unmasked Diabetes Insipidus in a Case of IgG4-related Retroperitoneal Fibrosis and Tuberoinfundibular Hypophysitis: A Case Report and Review of the Literature

The clinical picture of IgG4-related disease (IgG4-RD) is diverse because various organs can be affected. We describe the case of a 56-year-old man with acute renal failure and tuberoinfundibular hypophysitis due to IgG4-RD. Steroid therapy lowered the serum IgG4 level and ameliorated renal dysfunction, bilateral hydronephrosis and retroperitoneal fibrosis. However, polyuria from post-obstructive diuresis and unmasked central diabetes insipidus ensued. The patient's polyuria continued despite the administration of a therapeutic dose of glucocorticoid; the patient's pituitary swelling and anterior pituitary dysfunction were partially ameliorated. The pituitary swelling recurred seven months later. In patients with IgG4-RD, the manifestation of polyuria after steroid therapy should prompt suspicion of post-obstructive diuresis and the unmasking of central diabetes insipidus.

Phytochemical and biological assessments on Lipidium meyenii (maca) and Epimidium sagittatum (horny goat weed)

The effects of Lipidium meyenii (maca, LM) and Epimidium sagittatum (horny goat weed, ES) have been investigated due to their involvement in fertilization. Both of the drugs showed good results before, during and after fertilization in male and female mice. The results revealed that the crude extract of Lipidium meyenii caused a significant decrease in the no. of writhes at 300 and 500mg/kg (p<0.05) as compare to control, Epimidium sagittatum and standard drug. The gross behavioral, open field, exploratory behaviour, forced swimming test for stress, diuretic activity, chronic toxicity with the effect on reproduction of both male and female and change in body weight were also studied. The phytochemical study showed the presence of tannin, alkaloid, carbohydrate, rich protein and absence of sterol in LM, whereas ES shows presence of sterol and less protein. LS improve in muscle activity and exploratory behaviours without any toxic effects on mice and their pups. It does not have diuretic effect for first two hour but act normally after initial phase of drug therapy. Epimidium sagittatum has dual action that is at low dose it has slight stimulation action and at high dose little depressive effect. ES also has some diuretic effect. Overall these results suggest that LM is highly effective remedy for treatment of impotency and reduces stress and depression, because of dual effect ES not only suggested as an anxiolytic medicine but also effective in female hormonal disorder.

Effects of Cardiac Hormones on Arterial Pressure and Sodium Excretion in NPRA Knockout Mice

These studies were designed to determine if the atria contains natriuretic substances that act through a non–natriuretic peptide type A (NPRA) receptor mechanism. C57BL/6 mice, either wild-type NPRA++ (WT) or NPRA —- knockout (KO), were anesthetized with pentobarbital. Catheters were placed in the trachea, carotid artery, jugular vein, and bladder. Urine was collected for six 30-min periods. Both groups received an iv injection of 100 ng of rat atrial natriuetic peptide (rANP) in 200 μl of saline after the first period (30 mins) and 200 μl of rat atrial extract after the fourth period (120 mins). ANP injection increased urine flow (UF) to 2.7 ± 0.5 μl/min in the WT versus 1.9 ± 0.2 in KO. Extract increased UF to 7.9 ± 1.5 μl/min in WT versus 2.7 ± 0.4 in KO (P < 0.01). ANP increased sodium excretion (ENa) to 0.47 ± 0.10 μmoles/min in WT versus 0.27 ± 0.04 in KO (P < 0.05). Extract increased ENa to 1.44 ± 0.47 μmoles/min in WT versus 0.26 ± 0.06 in KO (P < 0.05). Extract decreased mean arterial pressure (MAP) to 62 ± 3 mm Hg in the WT versus 81 ± 5 in KO (P < 0.01). ENa and MAP responses to extract in KO were not different from responses to 200 μl of saline. A constant 150-min infusion of rat atrial extract increased urine flow by 3-fold and ENa by 5-fold (both P < 0.05) in the WT mice but had no significant effect in the KO mice. Thus, acute renal and MAP responses to atrial extracts require the NPRA receptor.

Atrial Natriuretic Peptide Stimulates Dopamine Tubular Transport by Organic Cation Transporters: A Novel Mechanism to Enhance Renal Sodium Excretion

The aim of this study was to demonstrate the effects of atrial natriuretic peptide (ANP) on organic cation transporters (OCTs) expression and activity, and its consequences on dopamine urinary levels, Na⁺, K⁺-ATPase activity and renal function. Male Sprague Dawley rats were infused with isotonic saline solution during 120 minutes and randomized in nine different groups: control, pargyline plus tolcapone (P+T), ANP, dopamine (DA), D-22, DA+D-22, ANP+D-22, ANP+DA and ANP+DA+D-22. Renal functional parameters were determined and urinary dopamine concentration was quantified by HPLC. Expression of OCTs and D1-receptor in membrane preparations from renal cortex tissues were determined by western blot and Na⁺, K⁺-ATPase activity was determined using in vitro enzyme assay. ³H-DA renal uptake was determined in vitro. Compared to P+T group, ANP and dopamine infusion increased diuresis, urinary sodium and dopamine excretion significantly. These effects were more pronounced in ANP+DA group and reversed by OCTs blockade by D-22, demonstrating that OCTs are implied in ANP stimulated-DA uptake and transport in renal tissues. The activity of Na⁺, K⁺-ATPase exhibited a similar fashion when it was measured in the same experimental groups. Although OCTs and D1-receptor protein expression were not modified by ANP, OCTs-dependent-dopamine tubular uptake was increased by ANP through activation of NPR-A receptor and protein kinase G as signaling pathway. This effect was reflected by an increase in urinary dopamine excretion, natriuresis, diuresis and decreased Na⁺, K⁺-ATPase activity. OCTs represent a novel target that links the activity of ANP and dopamine together in a common mechanism to enhance their natriuretic and diuretic effects.

Allatostatin-C antagonizes the synergistic myostimulatory effect of allatotropin and serotonin in Rhodnius prolixus (Stal)

Haematophagous insects can ingest large quantities of blood in a single meal producing a large quantity of urine in the following hours to eliminate the excess of water and mineral ions incorporated. The excretory activity of the Malpighian tubules is facilitated by an increase in haemolymph circulation as a result of the intensification of aorta contractions, combined with an increase of anterior midgut peristaltic waves. We have recently shown that haemolymph circulation during post-prandial diuresis is modulated by the synergistic activity of allatotropin (AT) and serotonin, resulting in an increase in aorta and crop contraction rates. In the present study we describe the antagonistic effect of allatostatin-C (AST-C) on the increase of aorta frequency of contractions induced by serotonin/AT in Rhodnius prolixus. The administration of AST-C counteracted the increase in the frequency induced by the treatment with serotonin/AT, but did not affect the increase in frequency induced by the administration of serotonin alone, suggesting that AST-C is altering the synergism between serotonin and AT. Furthermore, the administration of AST-C during post-prandial diuresis decreases the number of peristaltic waves of the anterior midgut. The AST-C putative receptor is expressed in the hindgut, midgut and dorsal vessel, three critical organs involved in post-prandial diuresis. All together these findings provide evidence that AST-C plays a key role as a myoregulatory and cardioregulatory peptide in R. prolixus.

Simvastatin increases AQP2 urinary excretion in hypercholesterolemic patients: A pleiotropic effect of interest for patients with impaired AQP2 trafficking

We previously reported that statins improve the symptoms of X-linked nephrogenic diabetes insipidus (X-NDI) in animal models. The aim of this study was to verify whether the pleiotropic effect of statins on AQP2 trafficking and kidney-concentrating ability, observed in rodents, was attainable in humans at therapeutic doses. We enrolled 24 naïve hypercholesterolemic patients and measured urine excretion of AQP2 (uAQP2) at baseline and during 12 weeks of treatment with simvastatin 20 mg/day. Simvastatin induced a rapid and significant increase of uAQP2, reduced the 24-hour diuresis, and increased urine osmolality. These effects were also maintained in patients chronically treated with statins for at least 1 year. This study strongly suggests that statins may effectively enhance the efficacy of current pharmacological treatment of patients with urine-concentrating defects caused by defective AQP2 plasma membrane trafficking, like X-NDI.

Neural Substrate Essential for Suppression of Vasopressin Secretion and Excretion of a Water Load

Suppression of vasopressin secretion to very low levels is essential for the excretion of excess water. To investigate a role for the preoptic brain region in the suppression of vasopressin secretion and the excretion of a water load, lesions were made in the vicinity of the lamina terminalis in ewes (LTX-sheep) and responses to water-loading or reduction of cerebrospinal fluid NaCl by i.c.v. isotonic mannitol solution were investigated. In normal conscious sheep, intraruminal water-loading resulted in the urine flow rate increasing and urine osmolality decreasing within 1 h, such that renal free water clearance (CH 2O ) increased from -1.02 ± 0.16 ml/min (mean ± SEM) to a maximum of +4.99 ± 0.62 ml/min at 2.5 h after water-loading (P < 0.05, n = 6). Plasma vasopressin levels fell from 0.88 ± 0.17 pg/ml to undetectable levels (< 0.4 pg/ml, n = 4). In LTX-sheep (n = 6), CH 2O did not change significantly after water-loading (-1.78 ± 0.13 to -2.03 ± 0.49 ml/min at 2.5 h after water-loading). Plasma vasopressin levels were inappropriately elevated in water-loaded LTX-sheep (n = 3). Intracerebroventricular mannitol (1 ml/h for 2 h) resulted in a water diuresis and increase in CH 2O (-1.16 ± 0.12 to +2.81 ± 0.58 ml/min, P < 0.05) after 2 h in normal sheep, and plasma vasopressin levels fell significantly from to 0.88 ± 0.23 pg/ml to < 0.4 pg/ml (P < 0.05, n = 6). However, in LTX-sheep, there was no change in CH 2O (-1.31 ± 0.14 to -1.35 ± 0.12 ml/min) or the plasma vasopressin concentration (1.47 ± 0.18 to 1.60 ± 0.44 pg/ml, not significant) with i.c.v. mannitol. The results suggest that an inhibitory pathway from the vicinity of the median preoptic nucleus to the supraoptic and hypothalamic paraventricular nuclei plays an important role in the suppression of vasopressin secretion and the excretion of excess water.