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At least 919 records · Page 51Linked to original sources
PubMed1987

Antihypertensive drug therapy prevents cerebral microvascular abnormalities in hypertensive rats.

Studies were performed on anesthetized 16-18 week old normotensive Wistar-Kyoto rats, spontaneously hypertensive rats, and Goldblatt two-kidney one clip renal hypertensive rats, treated from age 4-5 weeks with an oral antihypertensive regimen consisting of hydralazine, reserpine, and chlorothiazide. Measurements of flow and intravascular pressure in the cerebral microvasculature were made via a constantly suffused open cranial window using video microscopy. A significant upward shift was seen in the pressure range for cerebral blood flow autoregulation in both groups of untreated hypertensive animals. Following treatment, the autoregulatory range in both hypertensive models was restored to a level nearly identical to control. The prevention of this shift in treated animals was due primarily to the prevention of structural microvascular adaptations that occur in untreated hypertensive animals. By preventing elevations in microvascular pressure, treatment may have eliminated the major stimulus for development of hypertrophy in resistance vessels. However, a persistent increment of arteriolar wall mass in treated spontaneously hypertensive rats may represent a hyperplastic response not influenced by treatment. Likewise, a persistent constriction of the smallest arterioles in treated renal hypertensive rats may represent a differential sensitivity of microvessels to circulating vasoactive agents. It appears that treatment initiated in the prehypertensive state, or before significant sustained hypertension has occurred, can markedly reduce the cerebrovascular morbidity associated with two different forms of hypertension.

Adaptation, Physiological↗
PubMed1967

The effects of infusion of water on renal hemodynamics and the tubular reabsorption of sodium.

Anesthetized dogs receiving an infusion of chlorothiazide and ethacrynic acid were given 600-ml infusions of distilled water or dilute dextrose solutions. The absolute rate of tubular sodium reabsorption was depressed, and the glomerular filtration rate was increased during the water loading, despite the associated decreases in plasma sodium concentration and decreases in the filtered load of sodium. The extent to which fractional sodium reabsorption decreased and the excretion of sodium increased was inversely related to the degree to which the filtered load of sodium was depressed as a result of the decreased plasma sodium concentration. We conclude that, in the presence of the diuretic blockade of distal tubular sodium reabsorption, infusion of water depresses proximal tubular reabsorption of sodium and that these changes are qualitatively similar to those previously observed during infusions of saline. Similar depression of tubular reabsorption of sodium and increased excretion of sodium occurred during water loading in the absence of diuretics in dogs undergoing saline diuresis, which presumably provided a high rate of distal sodium reabsorption before water loading. We suggest that volume expansion with water depresses proximal tubular reabsorption of sodium in a manner qualitatively similar to infusions of saline and that the extent to which sodium excretion is increased during water loading is dependent upon 1) the absolute extent to which proximal reabsorption is depressed, 2) the extent to which the filtered load of sodium is maintained in the presence of a falling concentration of sodium in plasma, and 3) the extent to which increased distal reabsorption compensates for the depressed proximal reabsorption of sodium. Mechanisms are suggested whereby the previously reported inverse relationship between plasma concentration of sodium and over-all tubular reabsorption of sodium may be only apparent, and could be the result of physiologic "glomerulotubular balance" during the specific experimental maneuvers.

Animals↗
PubMed1970

The effect of altered sodium concentration in the distal nephron segments on renin release.

Ethacrynic acid, a potent inhibitor of sodium reabsorption in the ascending limb of Henle's loop, produces a sharp rise in renal venous renin activity within 5 min after intravenous administration in anesthetized dogs. This response persists when volume depletion is prevented by returning urinary outflow to the femoral vein. Comparable studies with chlorothiazide, a diuretic with little or no effect on the medullary portion of the ascending limb of the loop of Henle, failed to produce a significant increase in renal venous renin activity.When administered during ureteral occlusion, ethacrynic acid produced no change in renal venous renin activity until ureteral occlusion was released and flow restored. Following release of the ureters, a prompt rise in renal venous renin was again observed within 5 min of release. Control studies of ureteral occlusion yielded a fall in renal venous renin activity following release of the ureter without administration of ethacrynic acid. These studies identify a prompt stimulatory effect of ethacrynic acid on renin release that is unrelated to volume depletion but dependent upon the presence of tubular urine flow. Although further definition of the site and characteristics of the distal tubular mechanism for stimulation of renin release requires more direct study, the data presented here indicate that changes in sodium concentration in distal tubular fluid serve as a stimulus for renin release.

Angiotensin II↗
PubMed1974

On the mechanism of lithium-induced diabetes insipidus in man and the rat.

The mechanism of lithium-induced diabetes insipidus was investigated in 96 patients and in a rat model. Polydipsia was reported by 40% and polyuria (more than 3 liter/day) by 12% of patients receiving lithium. Maximum concentrating ability after dehydration and vasopressin was markedly impaired in 10 polyuric patients and was reduced in 7 of 10 nonpolyuric patients studied before and during lithium therapy. Severe polyuria (more than 6 liter/day) was unresponsive to trials of vasopressin and chlorpropamide, but improved on chlorothiazide. Rats receiving lithium (3-4 meq/kg/day) developed massive polyuria that was resistant to vasopressin, in comparison to rats with comparable polyuria induced by drinking glucose. Analysis of renal tissue in rats with lithium polyuria showed progressive increase in the concentration of lithium from cortex to papilla with a 2.9-fold corticopapillary gradient for lithium. The normal corticopapillary gradient for sodium was not reduced by lithium treatment. The polyuria was not interrupted by brief intravenous doses of vasopressin (5-10 mU/kg) or dibutyryl cyclic AMP (10-15 mg/kg) capable of reversing water diuresis in normal and hypothalamic diabetes insipidus rats (Brattleboro strain). The present studies suggest that nephrogenic diabetes insipidus is a common finding after lithium treatment and results in part from interference with the mediation of vasopressin at a step distal to the formation of 3',5' cyclic AMP.

Animals↗
PubMed1977

Effects of acetazolamide on proximal tubule C1, Na, and HCO3 transport in normal and acidotic dogs during distal blockade.

It has been suggested that the establishment of a tubular fluid to plasma chloride gradient in the late proximal tubule by the reabsorption of bicarbonate (and other anions) in the early proximal tubule is responsible for a significant part of sodium chloride and water reabsorption in the proximal tubule. In the present study the effects of acetazolamide on proximal tubule water and electrolyte excretion were examined in 6 normal dogs and 10 chronic ammonium chloride-loaded dogs during distal blockade produced by ethacrynic acid and chlorothiazide administration. During distal blockade control urine/plasma osmolality and urine/plasma sodium were close to unity in all experiments. Urine/plasma chloride and urine/plasma bicarbonate were 1.21+/-0.02 and 0.75+/-0.07 in normal and 1.24+/-0.01 and 0.04+/-0.01 in acidotic dogs, respectively. After the administration of acetazolamide (20 mg/kg i.v.), there was a significant increase in urine flow, absolute and fractional excretion of sodium, bicarbonate, and chloride in all animals. Associated with these effects, urine/plasma osmolality and urine/plasma sodium remained unchanged but urine/plasma chloride decreased significantly to 1.15+/-0.01 in normal and to 1.19+/-0.01 in acidotic dogs. In acidotic dogs there was a significant correlation between the increase in bicarbonate, sodium, or chloride excretion after acetazolamide and the plasma bicarbonate level (range 6.8-12.5 meq/liter). These data demonstrate a significant effect of acetazolamide on bicarbonate, sodium, and chloride reabsorption in the proximal tubule even in the face of severe acidosis. Moreover, the data suggest that the decrease in chloride reabsorption (and accompanying sodium) after acetazolamide is related to the decrease in bicarbonate reabsorption and the associated decrease in the transtubular chloride gradient.

Acetazolamide↗
PubMed2002

Unexplained systemic hypertension after closure of ductus arteriosus.

Immediately after surgical closure of a patent ductus arteriosus, a 12-year-old boy developed severe systemic arterial hypertension refractory to medication. The cause of hypertension could not be found, but it came under control 3 weeks postoperatively with a combination of angiotensin-converting enzyme inhibitor and chlorothiazide.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1985

Impaired renal acidification in infants with fetal alcohol syndrome.

Urinary acidification was studied in six unrelated infants with fetal alcohol syndrome and eight healthy age-matched infants. Creatinine clearance, fractional sodium excretion, plasma renin activity, and plasma aldosterone were normal in all patients but fractional potassium excretion was lower in the patients than in the controls (p = 0.0001). After ammonium chloride loading, minimum urine pH was significantly higher in FAS patients than in control subjects (5.5 +/- 0.1 and 4.7 +/- 0.1, respectively, p = 0.00005). Net acid excretion was also lower in the patients (24.5 +/- 1.7 Eq/min) than in the controls (27.8 +/- 2.1 Eq/min, p = 0.008). Following sodium bicarbonate loading, fractional bicarbonate excretion was significantly higher (p = 0.00005) and fractional potassium excretion significantly lower (p = 0.002) in the patients than in the controls with comparable blood pH and bicarbonate levels. Treatment with chlorothiazide lowered plasma potassium and raised plasma bicarbonate to normal levels (p = 0.05). Concomitantly, fractional sodium excretion, fractional potassium excretion, and urinary net acid excretion increased significantly (p = 0.01). We conclude that patients with fetal alcohol syndrome have a defect in distal acidification and potassium excretion which cannot be attributed to abnormal aldosterone secretion.

Acidosis, Renal Tubular↗
PubMed1999

Alginate-pectin-poly-L-lysine particulate as a potential controlled release formulation.

Drug delivery particulates were prepared using alginate, polylysine and pectin. Theophylline, chlorothiazide and indomethacin were used as the model drugs for in-vitro assessments, and mannitol was the model for assessing paracellular drug absorption across Caco-2 cell monolayers. Alginate and pectin served as the core polymers and polylysine helped to strengthen the particulates. Use of pectin specially helped in forming a more robust particulate that was more resistant in acidic pH and modulated the release profiles of the encapsulated model drugs in the alkaline pH. Alginate and pectin were also found to enhance the paracellular absorption of mannitol across Caco-2 cell monolayers by about three times. The release rate could be described as a first-order or square-root time process depending on the drug load. Use of alginate-polylysine-pectin particulates is expected to combine the advantages of bioadhesion, absorption enhancement, and sustained release. This particulate system may have potential use as a carrier for drugs that are poorly absorbed after oral administration.

Adhesiveness↗
PubMed2005

Releasing the flood waters: diuril and the reshaping of hypertension.

This article narrates the development and promotion in the 1950s and 1960s of Merck, Sharp & Dohme's Diuril (chlorothiazide), an antihypertensive drug, which played a significant role in the redefinition of high blood pressure as a widespread target for chronic pharmaceutical consumption. The joined careers of Diuril and hypertension in the late twentieth century demonstrate the connections between the clinical research, clinical practice, and marketing practices through which pharmaceuticals and disease categories come to define one another. By examining a series of internal documents preserved in the Merck Archives alongside a careful reading of the clinical literature and industry journals of the time, this article explores how the ambitions of marketers, physicians, and public health advocates found convergence in the expanding pharmaceutical prevention of chronic diseases.

Antihypertensive Agents↗
PubMed1992

Fluid transport in a cultured cell model of kidney epithelial cyst enlargement.

Madin-Darby canine kidney (MDCK) cells, when seeded into collagen gel, from polarized, spherical, epithelial cysts, which grow by a process involving fluid secretion and cell proliferation. These cysts are a useful model for understanding the dynamics of cyst enlargement in renal cystic disease. The hypothesis that MDCK cyst fluid secretion depends upon chloride secretion was tested, and a cell model for this process is presented here. Lumen and epithelial cell volumes were measured by video microscopy in acute experiments. Fluid absorption (-0.073 +/- 0.007 microliters.h-1.cm-2; N = 8) was observed when cysts were superfused with unsupplemented Dublecco's modified Eagle's medium at 36 to 37 degrees C. Fluid secretion (0.221 +/- 0.0016 microliters.h-1.cm-2; N = 25) was seen when 1 mM dibutyryl cAMP plus 0.1 mM 3-isobutyl-1-methylxanthine were added to the superfusate. cAMP-induced fluid secretion was significantly inhibited by basolateral 1 mM ouabain, 0.1 mM furosemide, or 1 mM amiloride. It was not significantly affected by 1 mM chlorothiazide, 0.01 mM bumetanide, or 0.1 mM acetazolamide in the presence of normal bicarbonate/CO2. In the nominal absence of bicarbonate/CO2 fluid secretion was 18% of control. Vasopressin-induced fluid secretion was significantly inhibited by pretreatment of cysts with 0.1 mM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). Cyst cell shrinkage in isosmotic chloride-free Ringer's solution (chloride replaced by gluconate) was inhibited by 0.1 mM basolateral DIDS. The results suggest that chloride-bicarbonate exchange in the basolateral membrane of MDCK cyst epithelial cells plays a critical role in cyst fluid secretion.

1-Methyl-3-isobutylxanthine↗
PubMed1981

Thermoregulation in spontaneously hypertensive rats: effects of antihypertensive treatments.

Colonic temperature was measured in spontaneously hypertensive (SHR), Wistar Kyoto (WKY) and Wistar Charles River (WIS) rats. The SHRs had higher basal temperature and their temperature decreased more rapidly when exposed to 4 degrees C than temperature of controls. During exposure to 37 degrees C for 2 hrs no controls but majority of SHRs died. Treatment with clonidine (1 mg/kg, b.i.d., 14 days), hydralazine (10 mg/kg, b.i.d., 14 days) or diuretics (chlorothiazide 100 mg/kg + spironolactone 10 mg/kg, q.d., 21 days) decreased blood pressure of SHRs but did not normalize their body temperatures and heat sensitivity. These results indicate thermoregulatory dysfunction in SHRs which is probably of central origin.

Animals↗
PubMed1981

A search for a defect of proximal transport in denervated kidneys of conscious dogs.

The influence of renal nerves on proximal Na+ reabsorption was studied in clearance experiments with unilaterally renal-denervated conscious dogs prepared by surgical bladder division. Two types of experiments were made : A. maximal water diuresis, and B. Total blockade of distal NaCl reabsorption with ethacrynic acid and chlorothiazide. In maximal water diuresis CH2O + CNa was used as a measure of fluid delivery to the distal nephron. At similar GFR on both sides, the proximal reabsorption estimated as GFR--(CH2O + CNa) was 38.4 +/- 5.6 ml/min for the intact and 35.9 +/- 4.2 ml/min for the denervated kidney (n = 6, difference NS). After distal tubular blockade, proximal Na+ reabsorption calculated as filtered load minus urinary excretion was 3.84 +/- 0.43 mmol/min for the intact and 3.91 +/- 0.36 mmol/min for the denervated kidney (n = 6, difference NS). The fractional reabsorption of NA+ was 64.9 +/- 1.0% for the intact and 66.9 +/- 1.1% for the denervated kidney (difference NS). In contrast to data from renal denervation studies with anaesthetized animals, the present experiments did not show any difference in proximal reabsorption between the innervated- and denervated kidney. We conclude that in absence of anaesthesia renal efferent nerves have no major effect on NaCl transport in dog proximal tubule.

Animals↗
PubMed2000

Similarity in the linear and non-linear oral absorption of drugs between human and rat.

OBJECTIVE: The main aim of this study was to provide a simple, pharmacokinetic rationale for great similarity in the extent (Fab) of gastrointestinal absorption of about 100 different, diverse compounds between human and the rat in linear dosing range, and to test the general applicability of a novel empirical method to correlate the non-linear Fab between the human and the rat by normalizing doses by body surface area (BSA) or body weight 0.67. METHOD: The mean small intestinal transit time (t) of 36 rats was estimated from the reported study, and this was used to compare with that in humans. The reported great similarity in apparent first-order absorption rate constants (k) of seven structurally diverse compounds between the two species were obtained. Extensive computer search was made and non-linear Fab data for the two species were obtained for chlorothiazide, acyclovir, miglitol and pafenolol. RESULTS: The mean t for rats was estimated to be 3.32 h which is almost identical to that reported in humans. The great similarity in Fab between human and rat in linear absorption range can be rationalized by similar t and k between the two species. The markedly different Fab vs dose/kg of body weight profiles between human and rat for the four drugs showing dose-dependent Fab were found to collapse when doses were normalized by BW0.67. CONCLUSION: For Fab not limited by the solubility problem, the great similarity in Fab between human and rat in linear absorption range can be rationalized by the similar t and k. For non-linear Fab drugs, great similarity in Fab can also be obtained between human and rat when doses are normalized by BSA or BW0.67. Regardless of absorption properties (active, passive or facilitated), similar Fab between the two species may be generally obtained when doses used in humans are about 5 to 7 times lower than that in rats. The above findings may be valuable in drug development.

1-Deoxynojirimycin↗
PubMed1981

Hypertension treated by sodium restriction.

Forty-eight people with hypertension entered a controlled study to observe the effect of sodium (NaCl) restriction on blood pressure. In people with mild hypertension (diastolic blood pressure 90-105 mmHg), sodium restriction reduced blood pressure compared with a control group and 75% obtained a diastolic blood pressure of less than 90 mmHg. In people with more severe hypertension (diastolic blood pressure 4105 mmHg), sodium restriction achieved the same level of control as chlorothiazide (500 mg a day). Restriction of sodium intake is an effective method of reducing blood pressure and should be the first form of therapy in people with mild hypertension.

Adult↗
PubMed1975

Silent acute pancreatitis with encephalomalacia mimicking hepatic coma.

A very rare case of acute pancreatitis with concurrent encephalomalacia and ascites mimicking hepatic coma is described. The possibliity that the pancreatitis was caused by the administration of chlorothiazide in a diabetic patient is suggested as possible etiology. It is emphasized that when a cirrhotic patient develops coma, the possibility of painless,silent pancreatitis with encephalomalacia as well as hepatic coma should be considered in the differential diagnosis.

Acute Disease↗
PubMed1975

Changes in urea clearance after a single dose of diuretics during water diuresis.

The action of various diuretics on the excretion fraction of urea (Curea/Ccr) was studied in 91 healthy volunteers under conditions of maintained maximal water diuresis. On the basis of previous data on transtubular transport or urea it should be expected that with an increase in the excretion fraction of water (V/Ccr) under the given experimental conditions we should find an increase in Curea/Ccr. After administration of polythiazide, which has a predominantly distal localisation of action in the nephron, Curea/Ccr did not change. After administration of chlorothiazide, furosemide and after i.v. administration of ethacrynic acid there was a marked increase in V/Ccr, ranging from 5.4 to 18%. Despite this there was no significant increase in Curea/Ccr. After i.v. administration of acetazolamide or oral administration of ethacrynic acid Curea/Ccr even showed a statistically significant decrease. These findings suggest that a decrease in proximal tubular reabsorption of water after administration of diuretics during maximal water diuresis is not a decisive factor for the renal excretion of urea. The data suggest that the diuretics affected the permeability of the distal segment of the nephron for urea in the sense of an increase of tubular reabsorption.

Acetazolamide↗
PubMed1975

Effects of topically instilled drugs on intraocular pressure in rabbits.

The effect of the ocular instillation of some drugs on the intraocular pressure of non-anaesthetized rabbits was studied, using the Schiötz tonometer. The risk of systemic absorption of drugs follwoing ocular instillation was evaluated by 1. measuring the spreading of effects from the treated eye to the contralateral one and 2. studying the effects on blood pressure or on blood pressure responses to noradrenaline. The results showed that trazodone, epinephrine and acetazolamide produced hypotension on the treated eye; there was no spreading of effects to the contralateral one. These data could suggest that the primary site of action of these drugs is the eye. Naphazoline reduced the intraocular pressure both on the treated eye and, with a constant delay, on the contralateral one. This was interpreted as a combination of a local action and systemic absorption. The effects of chlorpromazien were more complex. This drug produced hypertension and a strong irritation on the treated eye as well as a hypotensive effect on the contralateral one. The rise in intraocular pressure was probably caused by irritation; the hypotensive effect by systemic absorption. The following drugs were inactive: amphetamine, chlorothiazide and pilocarpine.

Acetazolamide↗
PubMed1992

Bartter's syndrome: evidence suggesting a distal tubular defect in a hypocalciuric variant of the syndrome.

Renal tubular function was examined in 5 adult patients aged 18-30 years with Bartter's syndrome associated with renal magnesium wasting and hypocalciuria. In the 3 patients studied during hypotonic saline diuresis, distal tubular fractional chloride reabsorption was lower than that reported in normal subjects. In response to a single intravenous dose of furosemide (40 mg), the increment in the excretion of sodium, chloride, and magnesium was equal to or greater than in normal subjects, while in 2 patients, in response to intravenous chlorothiazide (500 mg), the increment in sodium excretion was less than in normal subjects. Magnesium chloride infusion was undertaken in 2 patients in order to compare magnesium and calcium excretions at similar plasma magnesium levels in patients and in normal subjects. The patients exhibited magnesium wasting only at normal or low plasma magnesium levels, while calcium excretion was reduced in the patients at normal and elevated plasma magnesium levels. We conclude that in these patients the enhancement of renal magnesium reabsorption by hypomagnesemia is defective, and the hypomagnesemia is not the cause of the hypocalciuria. The tubule defect responsible for these abnormalities of magnesium and calcium excretion may be located beyond the side of action of furosemide, in the thiazide-sensitive segment of the distal convoluted tubule.

Absorption↗