Rationale and design of a multicenter randomized study comparing the efficacy and safety of esaxerenone versus trichlormethiazide in patients with uncontrolled essential hypertension: EXCITE-HT study.

The next-generation mineralocorticoid receptor blocker (MRB) esaxerenone has favorable antihypertensive effects in patients who do not respond to treatment with first-line antihypertensive agents and may be beneficial as a second-line treatment. However, MRBs are currently considered a fourth-line treatment as there is no clinical evidence comparing the efficacy of esaxerenone with other classes of antihypertensive agents. The multicenter, randomized, open-label, parallel-group EXCITE-HT study will evaluate the efficacy and safety of esaxerenone as a second-line agent in the treatment of Japanese patients with uncontrolled essential hypertension. After a 4-week run-in period, patients will receive either esaxerenone or trichlormethiazide for 12 weeks per the package insert and the Japanese Society of Hypertension Guidelines for the Management of Hypertension. At Weeks 4 and 8, the dose of esaxerenone or trichlormethiazide may be increased. Blood pressure (home [morning and bedtime] and office), serum biomarkers, and urinary biomarkers will be measured. The primary efficacy endpoint is the change from baseline in morning home systolic blood pressure/diastolic blood pressure to the end of treatment. The EXCITE-HT study is expected to validate the non-inferiority of esaxerenone to trichlormethiazide and provide the first evidence for the early use of esaxerenone as a second-line agent in the treatment of Japanese patients with uncontrolled essential hypertension instead of its current use as a fourth-line agent.

Effect of amlodipine, efonidipine, and trichlormethiazide on home blood pressure and upper-normal microalbuminuria assessed by casual spot urine test in essential hypertensive patients.

The aim of this study was to assess the effects of irbesartan alone and combined with amlodipine, efonidipine, or trichlormethiazide on blood pressure (BP) and urinary albumin (UA) excretion in hypertensive patients with microalbuminuria (30≤UA/creatinine (Cr) ratio [UACR] <300 mg/g Cr) and upper-normal microalbuminuria (10≤UACR<30 mg/g Cr). This randomized controlled trial enrolled 175 newly diagnosed and untreated hypertensive patients (home systolic blood pressure [SBP]≥135 mmHg; 10≤UACR<300 mg/g Cr of casual spot urine at the first visit to clinic). All patients were treated with irbesartan (week 0). Patients who failed to achieve home SBP ≤125 mmHg on 8-week irbesartan monotherapy (nonresponders, n = 115) were randomized into three additional drug treatment groups: trichlormethiazide (n = 42), efonidipine (n = 39), or amlodipine (n = 34). Irbesartan monotherapy decreased home SBP and first morning urine samples (morning UACR) for 8 weeks (p < 0.0001). At 8 weeks after randomization, all three additional drugs decreased home SBP (p < 0.0002) and trichlormethiazide significantly decreased morning UACR (p = 0.03). Amlodipine decreased morning UACR in patients with microalbuminuria based on casual spot urine samples (p = 0.048). However, multivariate analysis showed that only higher home SBP and UACR at week 8, but not any additional treatments, were significantly associated with UACR reduction between week 8 and week 16. In conclusion, crucial points of the effects of combination therapy on UACR were basal UACR and SBP levels. The effect of trichlormethiazide or amlodipine treatment in combination with irbesartan treatment on microalbuminuria needs to be reexamined based on a larger sample size after considering basal UACR and SBP levels.

Combining irbesartan and trichlormethiazide enhances blood pressure reduction via inhibition of sympathetic activity without adverse effects on metabolism in hypertensive rats with metabolic syndrome.

Sympathoexcitation and oxidative stress in the brain have pivotal roles in hypertension with metabolic syndrome (MetS). Here, we examined whether oral administration of irbesartan (IRB) and trichlormethiazide (TCM) decreases blood pressure (BP) via inhibiting sympathetic activity through anti-oxidant effects in the brain of spontaneously hypertensive rats (SHR-cp). IRB/TCM treatment decreased BP more profoundly than IRB monotherapy. Urinary norepinephrine excretion and oxidative stress in the brain were decreased in both IRB and IRB/TCM groups without any adverse effect on the metabolic profile. These findings suggest that IRB/TCM profoundly decreases BP in SHR-cp by inhibiting sympathetic activity via anti-oxidant effects in the brain.

Diuretics prevent thiazolidinedione-induced cardiac hypertrophy without compromising insulin-sensitizing effects in mice.

Much concern has arisen regarding critical adverse effects of thiazolidinediones (TZDs), including rosiglitazone and pioglitazone, on cardiac tissue. Although TZD-induced cardiac hypertrophy (CH) has been attributed to an increase in plasma volume or a change in cardiac nutrient preference, causative roles have not been established. To test the hypothesis that volume expansion directly mediates rosiglitazone-induced CH, mice were fed a high-fat diet with rosiglitazone, and cardiac and metabolic consequences were examined. Rosiglitazone treatment induced volume expansion and CH in wild-type and PPARγ heterozygous knockout (Pparg(+/-)) mice, but not in mice defective for ligand binding (Pparg(P465L/+)). Cotreatment with the diuretic furosemide in wild-type mice attenuated rosiglitazone-induced CH, hypertrophic gene reprogramming, cardiomyocyte apoptosis, hypertrophy-related signal activation, and left ventricular dysfunction. Similar changes were observed in mice treated with pioglitazone. The diuretics spironolactone and trichlormethiazide, but not amiloride, attenuated rosiglitazone effects on volume expansion and CH. Interestingly, expression of glucose and lipid metabolism genes in the heart was altered by rosiglitazone, but these changes were not attenuated by furosemide cotreatment. Importantly, rosiglitazone-mediated whole-body metabolic improvements were not affected by furosemide cotreatment. We conclude that releasing plasma volume reduces adverse effects of TZD-induced volume expansion and cardiac events without compromising TZD actions in metabolic switch in the heart and whole-body insulin sensitivity.

Antioxidative effects of thiazide diuretics in refractory hypertensive patients. A randomized crossover trial of chlortalidone and trichlormethiazide.

Some thiazide diuretics seem to exert antioxidant effects, which may be beneficial in the management of hypertension. Although many large-scale clinical trials on hypertension have proved that thiazide diuretics confer significant reductions in stroke and cardiovascular events, most of these trials preferentially used chlortalidone. Therefore, the difference in antioxidant effects between chlortalidone (CAS 77-36-1; 12.5 mg/day) and another thiazide diuretic, trichlormethiazide (CAS 133-67-5; 1 mg/day) was studied. Forty patients with refractory hypertension even after treatment with a combination of a calcium channel blocker and an angiotensin II receptor blocker were randomly assigned to additionally receive either chlortalidone or trichlormethiazide for 6 months. Then, diuretics were switched in each patient and they were treated for another 6 months. Ambulatory blood pressure was monitored for 24 h and markers of inflammation (C-reactive protein) and oxidative stress (8-isoprostane, malondialdehyde-modified low-density lipoproteins) were measured before and after each treatment. Addition of chlortalidone resulted in a greater reduction of blood pressure (mean of 24 h; from 146.8 +/- 18.0/83.8 +/- 12.2 mmHg to 122 +/- 18/72 +/- 11 mmHg) than that of trichlormethiazide (134 +/- 18/ 78 +/- 11 mmHg, p < 0.001). The levels of C-reactive protein, malondialdehyde-modified low-density lipoproteins, and 8-isoprostane were lower after chlortalidone therapy than after trichlormethiazide therapy. These results suggest that chlortalidone is superior to trichlormethiazide in patients with essential hypertension.

Effects of an ARB on endothelial progenitor cell function and cardiovascular oxidation in hypertension.

BACKGROUND: Angiotensin II (Ang II) receptor blocker (ARB) has been reported to have protective effects on the cardiovascular system independent of blood pressure reduction. Endothelial progenitor cells (EPCs) play a significant role in neovascularization of ischemic tissue. The average lifespan of EPCs was recently reported to be shortened by oxidative stress and regulated by anti-oxidative mechanisms. It has been reported that EPCs are present in peripheral blood and have the ability to repair cardiovascular damage. We investigated the effects of an ARB, candesartan, on EPC function and cardiovascular oxidation in salt-loaded, stroke-prone, spontaneously hypertensive rats (SHR-SP) in vivo. METHODS: Salt-loaded SHR-SP were treated with candesartan (1 mg/kg/day), a diuretic (trichlormethiazide, TCM, 1.6 mg/kg/day), or an antioxidant (tempol, 5 mg/kg/day) for 2 weeks. Peripheral blood mononuclear cells (MNCs) were isolated and cultured to assay EPC colony formation and migration. Oxidative stress in EPCs was evaluated by thiobarbituric acid reactive substance (TBARS) assay. We evaluated messenger RNA (mRNA) expression of c-kit in the heart, the renin-angiotensin system (RAS) in EPC colonies, and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit in cardiovascular organs. RESULTS: Candesartan and tempol, but not TCM, markedly increased EPC colony number in SHR-SP and reduced TBARS. Candesartan also significantly decreased mRNA expression of NADPH oxidase subunits in cardiovascular organs and increased cardiac c-kit mRNA expression. EPCs expressed mRNAs of renin, cathepsin D, chymase, and Ang II type 1 and type 2 receptors. CONCLUSIONS: Candesartan, an ARB, improves EPC dysfunction and increases cardiac c-kit expression through the anti-oxidative mechanism in hypertension. The local RAS induces oxidative stress and regulates the EPC functions.

TARP auxiliary subunits switch AMPA receptor antagonists into partial agonists.

Quinoxalinedione compounds such as 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) are the most commonly used alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonists. However, we find that in the presence of transmembrane AMPA receptor regulatory proteins (TARPs), which are AMPA receptor auxiliary subunits, CNQX acts as a partial agonist. CNQX induced small depolarizing currents in neurons of the central nervous system, and reconstitution of this agonist activity required coexpression of TARPs. A crystal structure of CNQX bound to the TARP-less AMPA receptor ligand-binding domain showed that, although CNQX induces partial domain closure, this movement is not transduced into linker separation, suggesting that TARPs may increase agonist efficacy by strengthening the coupling between domain closure and channel opening. Our results demonstrate that the presence of an auxiliary subunit can determine whether a compound functions as an agonist or antagonist.

Upregulation of ligand, receptor system, and amidating activity of adrenomedullin in left ventricular hypertrophy of severely hypertensive rats: effects of angiotensin-converting enzyme inhibitors and diuretic.

OBJECT: We investigated the pathophysiological role of the cardiac adrenomedullin (AM) system, including the ligand, receptor and amidating activity in the hypertrophied heart in severe hypertension. METHOD: We studied the following four groups: control Wistar-Kyoto rats (WKY), spontaneously hypertensive stroke-prone rats (SHR-SP), 8 weeks captopril-treated SHR-SP, and 8 weeks trichlormethiazide-treated SHR-SP. AM precursor is converted to inactive glycine-extended AM (AM-Gly) and subsequently AM-Gly is converted to active mature AM (AM-m) by enzymatic amidation. We measured AM-m, AM-total (AM-T; AM-T = AM-m + AM-Gly), and atrial natriuretic peptide (ANP) in the plasma and left ventricle (LV) by immunoradiometric assay. We also measured gene expression of AM and ANP was and gene expression and protein levels of AM receptor system components such as calcitonin receptor-like receptor (CRLR), receptor-activity modifying protein (RAMP) 2 and RAMP3. RESULTS: At 7 weeks old, SHR-SP had higher blood pressure and ANP mRNA levels and lower plasma AM-T compared with WKY, however, there were no differences in other indices between the two groups. At 17 weeks old, SHR-SP had increased blood pressure, LV weight, plasma and LV ANP levels and mRNA levels of ANP compared with WKY. AM-m and AM-T levels in plasma (AM-m: + 31%; AM-T: + 56%) and the LV (AM-m: + 84%; AM-T: + 31%) were significantly higher in SHR-SP than in WKY. The LV tissue AM-m/AM-T ratio was significantly higher in SHR-SP (93.2%) than in WKY. The mRNA levels of AM, CRLR, and RAMP2 in the LV were significantly higher in SHR-SP than in WKY. Captopril and trichlormethiazide similarly decreased blood pressure and LV hypertrophy with the reduction of the LV AM-m and AM-T levels and mRNA abundance of AM and its receptor component. CONCLUSION: These results suggest that cardiac AM system is upregulated in the hypertrophied heart in this hypertension model. Considering that AM acts as an anti-remodeling autocrine and/or paracrine factor, upregulation of the AM system may modulate the pathophysiology in LV hypertrophy.

Renal effects of the calcium channel blocker aranidipine and its active metabolite in anesthetized dogs and conscious spontaneously hypertensive rats.

The purpose of this study was to investigate the renal effects of aranidipine, a novel calcium channel blocker of the dihydropyridine type, and its active metabolite in anesthetized dogs and conscious spontaneously hypertensive rats (SHRs). When infused into the renal artery in anesthetized dogs, aranidipine (0.03 microg/kg/min) induced sustained increases in urine volume and urinary excretion of sodium and of potassium. This effect was greater than that elicited by nifedipine (0.1 microg/kg/min). The aranidipine metabolite, M-1 (0.1 microg/kg/min), also caused diuresis and natriuresis almost equal to those of nifedipine. The stop-flow experiment using the anesthetized dog showed that intrarenal infusion of aranidipine (0.03 microg/kg/min), as well as nifedipine (0.1 microg/kg/min), produced natriuresis at the distal tubular site rather than at the proximal site. Aranidipine (0.3, 1, and 3 mg/kg), when administered orally, dose-dependently increased urine volume and urinary excretion of electrolytes in conscious saline-loaded SHRs. M-1 (10 mg/kg, p.o.) also showed diuretic and natriuretic effects comparable to those of nifedipine (10 mg/kg) in SHRs. In addition, after repeated oral administration of aranidipine for 7 days, short-term tolerance was not found for its diuretic and natriuretic effects in SHRs. These results suggest that, apart from antihypertensive efficiency, aranidipine may offer a therapeutic advantage by producing diuresis and natriuresis in hypertensive patients. The metabolite of aranidipine may contribute, in part, to the diuretic, natriuretic, and antihypertensive effects of aranidipine.

Molecular effects of M17055, furosemide and thiazide on cardiac hypertrophy of spontaneously hypertensive rats.

Although diuretics have been clinically shown to reduce cardiovascular morbidity and mortality, the effects of diuretics on cardiac hypertrophy are poorly understood. In this study, we examined the molecular effects of diuretics on hypertensive cardiac hypertrophy. Spontaneously hypertensive rats (SHR) were given p.o. M17055 (a novel "high ceiling" diuretic) 1.25, 2.5 or 5 mg/kg/day, furosemide 50 mg/kg/day or trichlormethiazide 30 mg/kg/day for 5 weeks. After the treatment, cardiac myosin isoforms were analyzed by gel electrophoresis, and cardiac hypertrophy-related gene expressions were examined by Northern blot analysis. These three diuretics significantly reduced cardiac hypertrophy of SHR. M17055 and furosemide, but not trichlormethiazide, significantly increased the proportion of cardiac V3 myosin of SHR by enhancing the gene expression of beta-myosin heavy chain. On the other hand, trichlormethiazide, but not M17055 or furosemide, suppressed the increased cardiac gene expression of skeletal alpha-actin in SHR. Cardiac collagen type III expression of SHR was decreased only by treatment with M17055. Plasma thyroid hormone levels of SHR were slightly decreased by M17055 and by furosemide and were negatively correlated with cardiac V3 myosin contents. Thus the effects on the gene expression of cardiac contractile proteins and collagen are significantly different among these three types of diuretics, which suggests that these diuretics may have different cardiac actions independent of their diuretic and antihypertensive actions. The increased cardiac V3 myosin induced by M17055 and by furosemide may be partially due to the decreased plasma thyroid hormone.

Antihypertensive effects of a new transdermal delivery system for clonidine in genetic and experimental hypertensive rats.

The antihypertensive effects of a new transdermal delivery system for clonidine (CAS 4205-90-7, clonidine tape, M-5041T) were investigated in spontaneously hypertensive rats (SHR), 2-kidney, 1-clip renal hypertensive rats (RHR) and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. M-5041T (0.5-4.5 mg/kg) elicited a long-lasting hypotensive effect that was accompanied by bradycardia in a dose-dependent manner during 24-h patching on the backs of rats in all three hypertensive rat models. The hypotensive effect of M-5041T was more persistent than that of oral administration of clonidine (50 and 100 micrograms/kg) in both SHR and RHR. The most pronounced hypotensive effect of M-5041T was observed in DOCA-salt hypertensive rats. Plasma clonidine concentrations following transdermal application of M-5041T (1.5 mg/kg) were approximately 2-3 fold higher in DOCA-salt hypertensive rats compared with SHR. Electrical conductance of the skin surface, an index of the water content of the stratum corneum, was greater in DOCA-salt hypertensive rats than in SHR, suggesting that the delivery of clonidine may have been enhanced as a result of an increase in skin permeability due to the increase in water content of the stratum corneum in DOCA-salt hypertensive rats. Co-administration of M-5041T (0.5 mg/kg) with either trichloromethiazide (1 mg/kg, orally) or nifedipine (3 mg/kg, orally) at each sub-dose which affected both systolic blood pressure and heart rate produced significant hypotensive and bradycardic effects in SHR. Following repeated daily applications of M-5041T (1.5 mg/kg) for 7 consecutive days in SHR, significant hypotensive and bradycardic effects were produced at 6 h post-patching and then disappeared at 24 h post-patching in each trial. The plasma clonidine concentrations at 6 and 24 h post-patching were similar from the first to the seventh trial. No significant changes in blood pressure and heart rate were observed after termination of the regimen. These findings suggest that M-5041T could serve as an efficient and useful antihypertensive transdermal delivery system in humans without producing tolerance to the hypotensive effect and withdrawal syndrome after abrupt cessation of the treatment when used alone or with either a diuretic or a calcium channel blocker.

Comparison of early and late start of antihypertensive agents and baroreceptor reflexes.

Along with arterial blood pressure reduction, maintenance of the integrity of baroreceptor reflex function contributes to preserving end-organ function in the treatment of hypertensive patients. The purpose of this study was to investigate the effects of antihypertensive agents (trichlormethiazide, atenolol, nicardipine, and enalapril) on baroreceptor reflex function by comparing early and late starts of treatment. We administered each agent to spontaneously hypertensive rats (SHR) as early-start groups from 10 to 36 weeks of age and as late-start groups from 28 to 36 weeks of age. We evaluated the gain of the reflex control of renal sympathetic nerve activity and heart rate using ramp infusions of phenylephrine and nitroglycerin in untreated SHR at 10, 28, or 36 weeks of age and in treated SHR at 36 weeks of age. In 28- and 36-week-old untreated SHR, the renal sympathetic nerve activity gain was not altered and the heart rate gain was decreased (from -2.3 +/- 0.3 to -1.3 +/- 0.3 and -1.2 +/- 0.3 beats per minute [bm]/mm Hg, P < .05, respectively) compared with 10-week-old SHR. Early and late start of therapy produced arterial pressure reductions (-18 +/- 4 and -12 +/- 5 mm Hg, P < .05, respectively). In the early-start groups, the renal sympathetic nerve activity gain was improved markedly in nicardipine- and enalapril-treated SHR (-4.2 +/- 0.2% and -4.9 +/- 0.2% of control/mm Hg, P < .01, respectively), and the heart rate gain was improved markedly in atenolol- and enalapril-treated SHR (-4.1 +/- 0.2 and -4.4 +/- 0.2 bpm/mm Hg, P < .01, respectively). In the late-start groups, the renal sympathetic nerve activity gain was improved moderately in nicardipine- and enalapril-treated SHR (-3.8 +/- 0.2% and -2.9 +/- 0.2% of control/mm Hg, P < .05, respectively). The heart rate gain was improved slightly only in nicardipine-treated SHR (-1.9 +/- 0.2 bpm/mm Hg, P < .05). These results demonstrate that an early start of antihypertensive treatment improves baroreceptor reflex function markedly compared with a late start of treatment. This supports the hypothesis that a possible critical phase sensitive to intervention with antihypertensive treatment exists during the development of hypertension and indicates that the early start of antihypertensive treatment would be required in clinical practice.

Inhibition of human thiopurine methyltransferase by furosemide, bendroflumethiazide and trichlormethiazide.

RESULTS: Incubation in vitro of human recombinant and erythrocyte (RBC) thiopurine methyl transferase (TPMT) with furosemide, bendroflumethiazide and trichlormethiazide demonstrated inhibition of both enzyme preparations, with IC50 values of 170 microM, 360 microM and 1 mM, respectively. Kinetic studies revealed that the inhibition was mixed or non-competitive with regard both to the thiopurine substrate 6-mercaptopurine (6-MP) and the methyl donor S-adenosyl-L-methionine. CONCLUSION: Since S-methylation is a major pathway in the metabolism of thiopurines, our data point to the possibility of a clinically significant diuretic-thiopurine interaction in patients treated simultaneously with these drugs.

Antihypertensive effects of KW-3902, an adenosine A1-receptor antagonist, in Dahl salt-sensitive rats.

We determined the effects of KW-3902 (8-(noradamantan-3-yl)-1,3- dipropylxanthine), a novel adenosine A1-receptor antagonist, on the development of hypertension in Dahl salt-sensitive (Dahl-S) rats. KW-3902 (0.00017% w/w-0.017% w/w), fed with the diet, prevented the development of hypertension at 2-6 weeks in response to the high (8% w/w) NaCl diet. KW-3902 increased urine volume and sodium excretion and attenuated cardiac hypertrophy. In another series of the experiments employing the clearance method, KW-3902 (0.1 mg/kg, i.v.) increased urine volume, sodium excretion and lithium clearance in anesthetized Dahl-S rats. These results suggest that the antihypertensive effect of KW-3902 in Dahl-S rats is mediated via its natriuretic effect, the site of action being, at least partly, the proximal tubule. The adenosine A1-receptor antagonist may be effective for the treatment of salt-sensitive hypertension.

Effects of KW-3902, an adenosine A1-receptor antagonist, on ascites volume in puromycin aminonucleoside (PAN)-induced nephrotic rats.

We investigated the effects of KW-3902 (8-(noradamantan-3-yl)-1,3-dipropylxanthine), a potent adenosine A1-receptor antagonist, on the nephrotic edema induced by puromycin aminonucleoside (PAN; 100 mg/kg, i.v.) in rats. The treatment with PAN decreased urine volume and urinary excretions of sodium and potassium, resulting in the ascites formation in 7 days. In rats with the nephrosis, KW-3902 (0.01-1 mg/kg/day for 3 days, p.o.) showed diuretic effects and reduced the volume of ascites, as was the case with furosemide (30 mg/kg/day) and trichlormethiazide (1 mg/kg/day). These results suggest that even in the nephrotic state, the adenosine A1-receptor antagonist can be an effective diuretic to ameliorate edema.

Protective effects of KW-3902, an adenosine A1-receptor antagonist, against cisplatin-induced acute renal failure in rats.

We investigated possible renal protective and therapeutic effects of KW-3902 (8-(noradamantan-3-yl)-1,3-dipropylxanthine), a novel and potent adenosine A1-receptor antagonist, on cisplatin-induced acute renal failure (ARF). ARF was induced in rats by a single injection of cisplatin-induced acute renal failure (ARF). ARF was induced in rats by a single injection of cisplatin (5 mg/kg, i.v.). Prophylactic treatment with KW-3902 (0.01-1 mg/kg, p.o., twice a day) significantly attenuated the increases of serum creatinine (S-CRE) and urea nitrogen (S-UN) induced by cisplatin. On the other hand, neither furosemide nor trichlormethiazide showed any ameliorating effects against the cisplatin-induced ARF. In the clearance study, the cisplatin-treatment induced marked decreases of glomerular filtration rate (GFR), renal plasma flow (RPF), and reabsorptions of water, sodium and potassium at tubular sites, in comparison with those in untreated normal rats. KW-3902 (0.1 mg/kg, p.o., twice a day) significantly improved these deteriorated glomerular and tubular functions. In the rats with established cisplatin-induced ARF, KW-3902 ameliorated the cisplatin-induced reductions of GFR, RPF, and reabsorptions of water, sodium and potassium at tubular sites. These results suggest that activation of adenosine A1-receptors is involved in the pathogenesis of cisplatin-induced ARF. The adenosine A1-receptor antagonist may be useful for the treatment of cisplatin-induced ARF.

Characterization of Na+ transport across the cell membranes of the ascending thin limb of Henle's loop.

In the ascending thin limb of Henle's loop (ATL), intracellular Na+ is extruded by Na+/K+ ATPase in the basolateral membrane. To further characterize Na+ transport across the cell membranes of the ATL, the intracellular sodium concentration ([Na+]i) was monitored using a sodium-sensitive fluorescent probe, SBFI, in the in vitro microperfused hamster ATL. Basal [Na+]i was 19.0 +/- 1.2 mM (N = 24). Removal and replacement of luminal Na+ did not change [Na+]i in the presence of Na+ in the bathing fluid. In contrast, luminal Na+ removal reduced [Na+]i from 11.6 +/- 0.9 to 6.3 +/- 0.8 mM in the absence of peritubular Na+ (P < 0.0005, N = 21). Replacement of luminal Na+ increased [Na+]i to 12.6 +/- 0.9 mM. In the absence of Na+ in the bath, the addition of 1 microM benzamil, 0.1 mM 5-(N,N-dimethyl)-amiloride (DMA), 0.1 mM furosemide, or 0.1 mM trichlormethiazide to the lumen did not change [Na+]i or the rate of change in [Na+]i/dt) after removal and replacement of luminal Na+. Decreases in luminal pH in a Hepes-buffered solution and luminal HCO3- did not affect [Na+]i. In the absence of peritubular Na+, DMA in the bathing fluid decreased [Na+]i from 11.4 +/- 1.3 to 6.4 +/- 1.2 mM (P < 0.01, N = 5) and completely inhibited the changes in [Na+]i after removal and replacement of luminal Na+. Removal of peritubular Na+ reduced [Na+]i from 18.8 +/- 1.2 to 11.3 +/- 0.7 mM (P < 0.0001, N = 23). Addition of DMA in the bathing fluid reduced [Na+]i and inhibited the changes in [Na+]i after removal and replacement of peritubular Na+.(ABSTRACT TRUNCATED AT 250 WORDS)

Antihypertensive effects, determined by a telemetry method, of trichloromethiazide and 7-O-ethylfangchinoline, a derivative of tetrandrine, in spontaneously hypertensive rats.

1. The antihypertensive effects of 10 mg/kg trichloromethiazide (TCM), 10 mg/kg 7-O-ethylfangchinoline (7-O-EFC) and the combination of these drugs given orally once daily for 2 weeks were investigated by measuring the blood pressure (BP), heart rate (HR) and activity in conscious, freely moving spontaneously hypertensive rats (SHR) fitted with a telemetry device. 2. Clear diurnal rhythms of the HR and activity in synchrony with the light/dark cycle were observed during therapy, whereas the BP rhythm was obscure. 3. Alone, TCM and 7-O-EFC produced slight and insignificant reductions of 24h mean BP, whereas in combination they produced an additive and significant BP reduction, compared with the vehicle-treated controls, from the third day of therapy. The BP reduction induced by the combination of these drugs during the dark phase was more marked than that during the light phase. 4. None of the drug therapies affected the HR and activity diurnal rhythms. 5. The results of the present study demonstrate that the telemetry method is useful for monitoring the antihypertensive effects of drugs in SHR under physiological conditions with minimal stress.

Diuretic effects of KW-3902, a novel adenosine A1-receptor antagonist, in anesthetized dogs.

The effects of intravenous infusion of KW-3902 (8-(noradamantan-3-yl)-1,3-dipropylxanthine), a novel adenosine A1-receptor antagonist, on urine volume, urinary excretion of electrolytes and renal hemodynamics were examined in anesthetized dogs. KW-3902 at 10 and 30 micrograms/kg/min for 20 min inhibited the decline of renal blood flow induced by intrarenal arterial injection of adenosine (0.5-2.0 micrograms). KW-3902 at these doses produced significant increases in urine volume and sodium excretion with little change in potassium excretion. The diuretic effect of KW-3902 at 30 micrograms/kg/min for 20 min continued for longer than 1 h even after discontinuation of the KW-3902 infusion. KW-3902 did not affect creatinine clearance, renal blood flow, arterial blood pressure or heart rate. Furosemide at 10 micrograms/kg/min for 20 min brought about significant increases in urine volume and excretion of sodium and potassium. The diuresis and saliuresis induced by furosemide continued for only 40 min after discontinuation of the drug infusion. Trichlormethiazide at 3 micrograms/kg/min for 20 min also provoked increases in urine volume and sodium excretion, but did not affect potassium excretion. The diuretic and natriuretic effect of trichlormethiazide gradually disappeared after discontinuation of the drug infusion. The present study in anesthetized dogs suggests that KW-3902, an adenosine A1-receptor antagonist, produces diuresis and natriuresis but not kaliuresis and that the diuresis and natriuresis are caused in large part by the inhibition of sodium reabsorption at tubular sites.

Antihypertensive effects of a novel calcium antagonist, semotiadil fumarate (SD-3211), alone and in combination with enalapril or trichlormethiazide in spontaneously hypertensive rats.

Semotiadil fumarate, a novel benzothiazine calcium antagonist, was given alone or in combination with either enalapril or trichlormethiazide to conscious, spontaneously hypertensive, rats daily for 2 weeks. Systolic blood pressure and heart rate were recorded 24 h before the start of the regimen and then every 2 and 24 h after the 1st, 3rd, 7th, 10th and 14th doses. When given alone, the antihypertensive effects of semotiadil (10 mg/kg, p.o.) and enalapril (5 mg/kg, p.o.) first became apparent after the 3rd dose and thereafter the effects appeared to develop daily although this effect had waned by the time of the next dose. When given in combination, however, these drugs appeared to potentiate each other and after the 7th dose, the antihypertensive effect persisted. Trichlormethiazide (30 mg/kg, p.o.) alone failed to exert any significant antihypertensive effect and in combination was not always additive to that of semotiadil. In contrast to the effect on blood pressure, the heart rate remained resistant to all these drugs. These results indicate that combined daily dosing of semotiadil, especially with enalapril, each at relatively low doses may be able to control hypertension in a continuous manner.