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At least 19 recordsLinked to original sources
PubMed2003

N-Glycosylation at two sites critically alters thiazide binding and activity of the rat thiazide-sensitive Na(+):Cl(-) cotransporter.

The rat thiazide-sensitive Na-Cl cotransporter (rNCC) is expressed in the renal distal convoluted tubule and is the site of action of an important class of antihypertensive agents, the thiazide diuretics. The amino acid sequence contains two potential N-linked glycosylation consensus sites, N404 and N424. Either enzymatic deglycosylation or tunicamycin reduced the cotransporter to its core molecular weight (113 kD). Glycosylation site single mutants expressed in oocytes ran as thick bands at 115 kD, consistent with the high-mannose glycoprotein. The double mutant produced the single thin 113-kD band seen in the deglycosylated cotransporter. Functional expression of cotransporters in Xenopus laevis oocytes revealed that the mutants displayed drastically decreased thiazide-sensitive (22)Na(+) uptake compared with wild-type NCC. Analysis of enhanced green fluorescence protein (EGFP)-tagged cotransporters demonstrated that this decrease in function is predominantly secondary to decreased surface expression. The elimination of glycosylation in the double mutant increased thiazide sensitivity by more than two orders of magnitude and also increased Cl(-) affinity. Thus, we have demonstrated that rNCC is N-glycosylated in vivo at two sites, that glycosylation is essential for efficient function and surface expression of the cotransporter, and that the elimination of glycosylation allows much greater access of thiazide diuretics to their binding site.

Animals↗
PubMed1985

Correction of hypocitraturia and prevention of stone formation by combined thiazide and potassium citrate therapy in thiazide-unresponsive hypercalciuric nephrolithiasis.

Thirteen patients with hypercalciuric calcium nephrolithiasis continued to form calcium stones when treated with thiazide (4.69 +/- 6.62 [mean +/- SD] stones per patient-year to 5.12 +/- 10.87 stones per patient-year), despite adequate hypocalciuric response (a reduction in urinary calcium levels from 303 +/- 119 mg per day to 193 +/- 88 mg per day, p less than 0.01). Because they had hypocitraturia (250 +/- 86 mg per day versus 643 +/- 236 mg per day in normal subjects, p less than 0.001), potassium citrate (10 to 20 meq three times per day) was added to the ongoing treatment program. During combined treatment with thiazide and potassium citrate, urinary pH significantly rose, and normal levels of urinary citrate were restored. Ten patients stopped forming new stones and all 13 had reduced stone formation rate. Thus, potassium citrate supplementation should be considered in patients requiring thiazide therapy for the control of hypercalciuric nephrolithiasis, especially if they have concurrent hypocitraturia or if it develops during thiazide therapy.

Adult↗
PubMed1986

Thiazide treatment of hypertension. Effects of thiazide diuretics on serum potassium, magnesium, and ventricular ectopy.

Thiazide diuretics are considered to be the cornerstone of contemporary antihypertensive therapy and are generally recommended as the initial treatment for patients with mild to moderate, uncomplicated hypertension. Hypokalemia and hypomagnesemia are two metabolic alterations that are associated with long-term thiazide therapy. Thirty-five patients (20 with low renin status and 15 with normal renin status) with mild to moderate essential hypertension were treated with hydrochlorothiazide in a dose-titration experiment after a four-week lead-in period. The initial daily dose was 12.5 mg; this was increased at four-week intervals to 25 mg, 37.5 mg, and 50 mg daily. The endpoint dose of this titration was that dose at which the patient's blood pressure normalized, or the dose of 50 mg, if that dose was reached. Patients were maintained on their endpoint dose of hydrochlorothiazide for 24 weeks of continuous thiazide monotherapy beyond the dose titration. The serum potassium and serum magnesium levels during the control period were 4.4 +/- 0.2 mmol/liter and 2.30 +/- 0.08 mg/dl, respectively. During dose titration, each incremental increase of hydrochlorothiazide produced a decrease in blood pressure and a stepwise decrease in serum potassium and magnesium levels. A previously reported study involving 38 patients with mild to moderate hypertension (22 with low renin status and 16 with normal renin status) used similar methods to study higher-dose thiazide therapy. An initial dose of 50 mg daily of hydrochlorothiazide was administered; this was increased at four-week intervals to 100 mg, 150 mg, and 200 mg. The serum potassium and serum magnesium levels during the control period were 4.5 +/- 0.2 mmol/liter and 2.1 +/- 0.18 mg/dl, respectively. In the hypertensive patients with normal renin status, doses of hydrochlorothiazide greater than 50 mg did not result in further blood pressure lowering effects; however, the undesirable effects of hypokalemia and hypomagnesemia continued to be manifested and increased at higher doses of hydrochlorothiazide. Thirty-eight patients who had previously experienced hypokalemia, palpitations, or cardiac arrhythmia were placed on hydroclorothiazide therapy for one to three months and were monitored for arrhythmias after treadmill exercise. The occurrence of premature ventricular contractions correlated significantly with the decrease in serum potassium (r = 0.73, p less than 0.001) and serum magnesium (r = 0.68, p less than 0.001) levels during hydrochlorothiazide therapy and with the product of the change of the two cations (r = 0.81, p less than 0.001).

Arrhythmias, Cardiac↗
PubMed1983

Lack of effect of beta-blocker on flat dose response to thiazide in hypertension: efficacy of low dose thiazide combined with beta-blocker.

Increasing the dose of a thiazide diuretic used alone in patients with essential hypertension has little further effect on blood pressure but increases the deleterious metabolic consequences of the diuretic. The effect of a beta-blocker on this flat dose response is not known. In two randomised crossover studies the effect of 12.5 mg, 25 mg, and 50 mg hydrochlorothiazide combined with 400 mg acebutolol was assessed. The mean fall in supine blood pressure was about 15% and was the same whatever dose of thiazide was used with the beta-blocker. As the dose of hydrochlorothiazide was increased, however, there was evidence of increasing metabolic consequences of the diuretic. The study did not define the minimum dose of diuretic, and doses of hydrochlorothiazide lower than 12.5 mg might be as effective. These results suggest that many patients who are being treated with a combination of a beta-blocker and a diuretic are receiving unnecessarily large amounts of the diuretic without benefit to their blood pressure and with adverse metabolic consequences.

Acebutolol↗
PubMed1976

Relative value of beta blockers and thiazides for initiating antihypertensive therapy. Beta blockers or thiazides in hypertension.

Fifty-five patients with mild to moderate, renal or essential hypertension were admitted to a double blind cross-over trial of 18 weeks, involving treatment periods with placebo, the thiazide bendrofluazide (15 mg daily) and the beta blocker atenolol (600 mg daily). Compared to the placebo period (190/117 mm Hg) the hypotensive effect of atenolol (-24/16 mm Hg) was more pronounced than the hypotensive effect of bendrofluazide (-17/6 mm Hg). Arguments in favor of initiating antihypertensive drug therapy with beta blocker were its more powerful hypotensive effect, the quicker onset of its action, less metabolic disturbance, decreased frequency of complaints and patient's preference. On thiazides body weight and the frequency of swollen ankles decreased. Plasma renin concentration was not found to have a strong predicting power for the hypotensive effect of atenolol or bendrofluazide but low renin patients showed a more pronounced blood pressure decrease on bendrofluazide and high renin patients, especially essential hypertensives, on atenolol. While these points can be a guide to therapy today, the preference of one drug over the other must eventually be based on their relative efficacy in decreasing morbidity and mortality from the hypertensive disease.

Adrenergic beta-Antagonists↗
PubMed1996

Comparison of captopril-thiazide and enalapril-thiazide combinations in the management of mild to moderate black hypertensive patients: how important is diuretic dose and duration of action of the ACE-inhibitor?

A double-blind, randomized, parallel-group study was performed to compare the efficacy and tolerability of captopril-thiazide and enalapril-thiazide combinations. After a 3-week placebo run-in period, 47 Black patients with mild to moderate essential hypertension (mean 24-hour diastolic blood pressure (BP) > 90 mmHg and < 115 mmHg) were randomized to receive 1 of 2 combination tablets: captopril 50 mg plus hydrochlorothiazide 25 mg (CAP, n = 24) or enalapril 20 mg plus hydrochlorothiazide 12.5 mg (COR, n = 23) once daily. After 12 weeks of active treatment the mean 24-hour ambulatory BP was reduced from 152 +/- 11/99 +/- 6 to 133 +/- 13/86 +/- 7 mmHg (p < 0.005) in the CAP group and 157 +/- 15/100 +/- 6 to 141 +/- 18/90 +/- 12 in the COR group (p < 0.005). Target BP (24-hour diastolic BP < 90 mmHg) was achieved in 75% (18/24) of patients on CAP and 48% (11/23) on COR (p = n.s.). 24-hour BP load fell significantly with both CAP (from 69% to 34%, p < 0.001) and COR (from 67% to 37%, p < 0.001). Left ventricular mass index decreased by 7% with CAP and 11% with COR. Cardiac index and fractional shortening remained essentially unchanged in both groups. Both treatments were well tolerated and overall incidence of side effects was very low. It is concluded that both CAP and COR are effective, safe first-line antihypertensive choices in Black patients with mild to moderate hypertension with the former showing a trend towards greater efficacy than the latter.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

A comparison of blood lipid and blood pressure responses during the treatment of systemic hypertension with indapamide and with thiazides.

Thiazide diuretics in high dosage adversely affect the lipid profile. The non-thiazide indoline, indapamide, appears to be free of this effect, but it is unclear whether this apparent metabolic advantage of indapamide is superior to thiazides used in low dose. Since there are no large direct comparative studies to test this distinction, I surveyed the literature and pooled the findings of all published reports giving data on lipid and blood pressure effects of thiazides in various doses and of both indapamide, 2.5 mg daily, used as monotherapy of hypertension. I found 31 reports of thiazides; 12 of them examined low-dose regimens, i.e., < or = 25 mg/day of hydrochlorothiazide or its equivalent in other thiazides. Larger doses of thiazides were tested in 19 studies (median daily dose of 50 mg, maximum dose of 112.5 mg). There were 430 subjects in the low-dose studies and 559 subjects in the high-dose regimens. There were 13 studies of indapamide, comprising 558 subjects. Regarding lipids, total cholesterol increased from baseline by 1.4% on indapamide, 3.8% on low-dose thiazides, and 6.3% on high-dose thiazides, The change from baseline was significantly greater for high-dose thiazides than for indapamide (p<0.01). Changes in high-density lipoprotein cholesterol did not differ among groups. The change in triglycerides differed among regimens, -0.5%, 10.8%, and 19.5% for indapamide, low-dose thiazides, and high-dose thiazides, respectively (p<0.01). Systolic blood pressure (SBP) decreased by 13 and 18 mm Hg on low-dose and high-dose thiazides, respectively (p<0.05 between doses). Indapamide lowered SBP by 16 mm Hg, not different from either thiazide dose. Diastolic blood pressure did not differ among groups. From these noncomparative studies, I conclude that (1) indapamide has no adverse lipid effect and lowers blood pressure equally to thiazides; (2) thiazide effects on lipids and SBP are dose-dependent; and (3) thiazides adversely affect the lipid profile even in low dose.

Antihypertensive Agents↗
PubMed1993

Effects of thiazide diuretic therapy on bone mass, fractures, and falls. The Study of Osteoporotic Fractures Research Group.

OBJECTIVE: To determine the relation between the use of thiazide diuretics and bone mass, fractures, and falls in older women. DESIGN: Cross-sectional study of thiazide diuretics, bone mass, and prevalent vertebral deformities; cohort analysis of thiazide diuretics and nonspinal fractures and falls. SETTING: Four clinical centers located in Baltimore, Maryland; Minneapolis, Minnesota; Portland, Oregon; and the Monongahela Valley, Pennsylvania. PARTICIPANTS: A total of 9704 ambulatory, nonblack women who were 65 years or older. MEASUREMENTS: Information on thiazide use, demographic data, medical history, and anthropometric measurements were obtained by questionnaire, interview, and examination. Appendicular bone mass was measured by single-photon absorptiometry. Incident falls and fractures were ascertained every 4 months. RESULTS: Women using thiazide diuretics for more than 10 years had significantly higher bone mass than women who had never used thiazide diuretics (for example, 0.381 g/cm2 compared with 0.355 g/cm2 for the distal radius [P < 0.001]). Current users of thiazide diuretics had an incidence of falls (relative risk, 1.06; 95% CI, 0.90 to 1.25) that was similar to that of those who had never used these drugs. After adjusting for age, body weight, functional status, total calcium intake, duration of estrogen replacement therapy, and self-reported health status, we found that current users of thiazide diuretics who had taken these drugs for more than 10 years had a risk for nonspinal (relative risk, 0.99; CI, 0.81 to 1.20) and osteoporotic (relative risk, 0.98; CI, 0.79 to 1.22) fractures that was similar to that of women who had never used thiazides; however, thiazide users did have a lower risk for fractures of the hip (relative risk, 0.63; CI, 0.34 to 1.16) and wrist (relative risk, 0.66; CI, 0.40 to 1.08), neither of which was significant. CONCLUSIONS: Thiazide diuretics have no effect on a women's risk for falling or for experiencing nonspinal fractures. The trend toward a lower risk for hip and wrist fractures is consistent with findings in previous cohort studies but may reflect selection factors for the use of thiazide diuretics. A randomized trial is needed to determine the effect ot thiazide diuretics on the incidence of fractures.

Accidental Falls↗
PubMed1997

Thiazide diuretics and the initiation of anti-gout therapy.

While physiologic and epidemiologic evidence link diuretic therapy with hyperuricemia, no previous study has quantified the risk for initiation of treatment specific for hyperuricemia or gout among elderly patients taking thiazide diuretics. We performed a retrospective cohort study of 9249 enrollees aged 65 or older in the New Jersey Medicaid program who were newly started on an antihypertensive medication from November 1981 through February 1989 and who had no prior use of anti-gout therapy (allopurinol, colchicine, or a uricosutic) during the preceding one-year period. We used Cox proportional hazards analysis to determine the risk for the initiation of anti-gout therapy in patients using various antihypertensive treatment regimens relative to no antihypertensive exposure. Patient follow-up extended for up to two years. Antihypertensive exposure was characterized over the entire period of follow-up according to the following categories: thiazide diuretic therapy alone; non-thiazide antihypertensive therapy; thiazide diuretic therapy in combination with any non-thiazide antihypertensive agent(s); and no antihypertensive use. Antihypertensive exposure was entered into the model as a time-varying covariate. Estimates of risk were adjusted for age, sex, race, nursing home residence, number of prescriptions filled, intensity of physician use, hospitalization history, and year of antihypertensive treatment initiation. The adjusted relative risk for the initiation of anti-gout therapy was 1.00 (95% CI, 0.65-1.53) for non-thiazide antihypertensive therapy alone, 1.99 (95%, CI, 1.21-3.26) for thiazide diuretic therapy, and 2.29 (95% CI, 1.55-3.37) for thiazide diuretic therapy in combination with any non-thiazide agent(s). Risk for anti-gout therapy was significantly increased for thiazide doses of > or = 25 mg/day (in hydrochlorothiazide equivalents); no significant increase in risk was seen for lower doses. We conclude that use of thiazide diuretics in doses of 25 mg/day or higher is associated with a significantly increased risk for initiation of anti-gout therapy. Such treatment may reflect the occurrence of clinical sequelae of diuretic-induced hyperuricemia or the inappropriate treatment of asymptomatic hyperuricemia.

Aged↗
PubMed2001

Increased bone mineral density in a population-based group of 70-year-old women on thiazide diuretics, independent of parathyroid hormone levels.

BACKGROUND: Several studies have shown greater bone mineral density (BMD) in people receiving thiazide diuretics compared with controls. Most researchers have related this association to the hypocalciuric effect of thiazides with subsequent rise in serum calcium and fall in parathyroid hormone (PTH) levels. Recent experimental evidence suggests, however, a direct effect of thiazides on osteoblast-like cells. OBJECTIVE: To test the hypothesis that the association of thiazides and raised BMD is independent of PTH levels in humans. SUBJECTS: A population-based group of 248 70-year-old Icelandic women, 51 receiving thiazide diuretics, 39 receiving other antihypertensive therapy and the rest acting as controls. MAIN OUTCOME MEASURES: The independent contribution of thiazide usage and PTH to BMD in a multivariate analysis. RESULTS: The mean BMD was 9.6% greater in the lumbar spine (P < 0.01) and 5.4% greater in the whole skeleton (P < 0.01) amongst thiazide users than in controls, reduced to 7.6% (P < 0.02) and 4.5% (P < 0.01), respectively, when corrected for fat mass which was 5.8 kg greater in the thiazide group. In a multivariate analysis, corrected for body weight and body composition, serum calcium and ln-PTH, thiazides remained a significant independent predictor of BMD in the total skeleton and lumbar spine, but not in the total hip or femoral neck. Thiazides explained about 3% of the variability in whole body and lumbar spine BMD. CONCLUSIONS: Thiazides augment or preserve BMD independent of PTH, implying other mechanisms.

Aged↗
PubMed2004

Thiazide-like diuretics attenuate agonist-induced vasoconstriction by calcium desensitization linked to Rho kinase.

Lowering blood pressure using thiazide-like diuretics, including chlorthalidone and hydrochlorothiazide, has been proven to be effective in clinical studies. However, the mechanisms by which thiazide-like diuretics lower blood pressure are still poorly understood. To evaluate whether thiazide-like diuretics cause calcium desensitization in smooth muscle cells, we measured their effects on agonist-induced increase of blood pressure in Wistar rats in vivo and on agonist-induced vasoconstriction of aortic rings, DNA synthesis, and protein synthesis, RhoA, Rho kinase, and intracellular calcium in vascular smooth muscle cells in vitro. Thiazide-like diuretics significantly attenuated angiotensin II-induced or norepinephrine-induced increase of systolic blood pressure in rats. Thiazide-like diuretics inhibited agonist-induced vasoconstriction of aortic rings in a concentration-dependent manner in the presence and absence of endothelium. The inhibitory effects of thiazide-like diuretics were similar to that of the specific Rho kinase inhibitor Y27632. RT-PCR and immunoblotting showed that RhoA and Rho kinase were significantly reduced in vascular smooth muscle cells after administration of thiazide-like diuretics. In contrast, thiazide-like diuretics did not affect protein tyrosine phosphatase-2 (SHP-2) expression. Agonist-induced changes of intracellular calcium were not affected by thiazide-like diuretics. The study indicates that thiazide-like diuretics inhibit agonist-induced vasoconstriction by calcium desensitization in smooth muscle cells linked to the Rho-Rho kinase pathway.

Acute-Phase Proteins↗
PubMed1994

Adrenocortical steroids increase renal thiazide diuretic receptor density and response.

The density of the rat renal pharmacologic receptor for thiazide-type diuretics, as quantitated by the maximal specific binding of (3H)metolazone, decreased to one-third normal after adrenalectomy. Selective glucocorticoid (dexamethasone or RU-28362) replacement increased thiazide receptor density to or above the normal level over the dose range of steroid that decreased thymus weight, which served as a bioassay for glucocorticoid activity. Mineralocorticoid (fludrocortisone or aldosterone), in doses that did not decrease thymus weight, also increased thiazide diuretic receptor density to or above normal. The addition of glucocorticoid (RU-28362) to maximal aldosterone increased thiazide receptor above that produced by aldosterone alone and to threefold normal. Similarly, the addition of aldosterone to high-dose RU-28362 also increased thiazide receptor density above that produced by the glucocorticoid alone and to threefold normal. Hence, the effects of glucocorticoids and mineralocorticoids appeared to be additive. The increase in renal thiazide receptor density produced by fludrocortisone, at a dose that elicited both mineralocorticoid and glucocorticoid effects, was unrelated to the basal (prethiazide) renal excretion of sodium, potassium, chloride, or calcium. However, fludrocortisone-pretreated animals responded to bendroflumethiazide with a greater natriuresis than did controls. In addition, the magnitudes of the thiazide-elicited natriuresis and chloriuresis correlated significantly with thiazide receptor. It was concluded that both the density of the renal thiazide receptor and the quantity of sodium and chloride reabsorbed by the thiazide-sensitive Na-Cl cotransporter in the kidney are under adrenocortical regulation.

Adrenalectomy↗
PubMed1992

Thiazide diuretics: first-line therapy for hypertension.

PURPOSE: To compare low-dose thiazides to beta-blockers, angiotensin converting enzyme (ACE) inhibitors, calcium antagonists and alpha-blockers for simplicity, tolerability, efficacy, safety and cost-effectiveness as first-line treatment for hypertension. METHOD: Review of short-term comparative studies, and the outcome of long-term trials with vascular complications of hypertension as endpoints. SIMPLICITY: Among the advantages of thiazides are a flat dose-response; no dose titration; effectiveness when used once a day; no first-dose hypotension; and few contra-indications. TOLERABILITY: Thiazides are the best tolerated agents in patients over the age of 60 years and in younger women. They sometimes cause gout and impotence in younger men, in whom beta-blockers are equally acceptable first-line therapy. EFFICACY: Thiazide-based regimens have consistently reduced vascular complications of hypertension, the real measure of efficacy. There is little evidence that regimens based on other drugs are effective in this sense. SAFETY: Concerns that thiazide-induced biochemical changes cause coronary events are baseless. An overview of outcome trials shows that thiazide-based treatment reduces coronary events significantly, and the reduction is not significantly different from that predicted by epidemiological data. Thiazide-based therapy has also reduced coronary events significantly and substantially in elderly patients with isolated systolic hypertension. COST-EFFECTIVENESS: Low-dose thiazide treatment needs minimal monitoring, and has proved most cost-effective in formal analyses. CONCLUSION: Low-dose thiazide treatment is a clear first-line choice for patients aged over 60 years and younger women, except those with diabetes or gout. In younger men there is little to choose between thiazides and beta-blockers.

Adrenergic alpha-Antagonists↗