Pharmacological and toxicological studies of binodaline hydrochloride

It has been shown, in extensive animal experiments, that 1-(omega-dimethylaminoethylmethyl)-amino-3-phenylindole hydrochloride (binodaline HCl, Sgd-Scha 1059), can be regarded as an antidepressant with novel characteristics. With anticholinergic and histamine-antagonistic effects almost completely lacking, the main effects of binodaline HCl are to increase noradrenergic influences and to produce CNS depression. The acute toxicity of binodaline HCl is comparatively low, and the good tolerance has been demonstrated in long-term studies in laboratory animals.

Radiochromium conservation and distribution in diuretic states

The effect of free water diuresis by three different modalities on body 51Cr conservation and distribution was studied in adult male rats. Despite massive diuresis, ADH deficiency had little effect on body 51Cr retention or relative tissue distribution of 51Cr but did induce 25-40% increases in serum 51C concentrations which were reversible by pitressin administration. Glucose feeding produced copious diuresis but no change in body 51Cr retention or relative tissue distribution of 51Cr. The serum 51Cr concentration decreased 23% in association with small increases in serum glucose and insulin concentrations. LiCl administration produced moderate diuresis with little change in body 51Cr retention and inconsistent changes in serum and tissue 51Cr distribution. These data indicate normal body retention of 51Cr despite body water pool turnovers of up to 100% per day. Hence, renal handling of Cr is flow-independent, presumably due to Cr reabsorption at a proximal site within the nephron. However, a marked restriction of Cr filtration by the glomerulus due to protein binding of Cr cannot be ruled out by these data. Differences in body weight, even if assumed to be due to altered extracellular fluid volume, are insufficient to account for the serum 51Cr data. Previous observations in adrenalectomized rats also do not support a role for aldosterone secretion secondary to extracellular fluid volume shifts. Therefore, the increase in serum 51Cr concentration in ADH deficiency may be due to an effect of ADH to promote cellular transport of Cr whereas the decrease in serum 51Cr concentration during glucose feeding is probably due to increased cellular penetration of Cr secondary to insulin action.

Impairment and restoration of rat urinary bladder responsiveness following distension

Micturition and bladder responsiveness in vitro were impaired in rats fed isotonic sucrose, afflicted with diabetes mellitus or diabetes insipidus. Their urinary output which was seven times control, initiated micturition responses at volumes three times control. Nerve-induced contractions by bladders from these rats developed substantially less pressure than control. Contractions elicited at 1 Hz by control and impaired bladders were potentiated equally by tetraethylammonium chloride (TEA) (5 mM) or by carbachol (2 X 10(-7) M). Contractions elicited at 20 Hz by normal bladders were not potentiated, those by impaired bladders were. TEA, by increasing transmitter release, and carbachol, by a postjunctional action, substantially reversed bladder dysfunction. Because control and impaired bladders were equally enhanced by TEA, prejunctional and contractile element (CE) activity at 1 Hz were probably unaffected by distension. However, postjunctional sensitivity was probably reduced. Impaired bladders, more compliant than controls, became less compliant after carbachol without elevating resting pressure. Whereas the action of carbachol to enhance bladder responsiveness did not involve tension development, there may have been cholinoceptor facilitation and shortening of CE.

Preoptic-hypothalamic periventricular lesions reduce natriuresis to volume expansion

The present experiment was designed to determine if electrolytic ablation of the periventricular tissue surrounding the anteroventral third ventricle (AV3V) altered the natriuresis typically seen during isotonic volume expansion. Control and AV3V-lesioned rats received intravenous infusions of 0.9% NaCl at 0.5 ml/min until 10% body weight was given. Arterial blood pressure was monitored, and urine was collected throughout the experiment. Following expansion, blood was processed for analysis of natriuretic hormonelike activity by chromatographic separation of plasma extracts followed by measuring antinatriferic activity across the isolated toad bladder. Urinary sodium excretion and urine volume during expansion were significantly less in rats with lesions surrounding the AV3V region than in control rats. Toad bladder bioassay showed a high level of natriuretic hormonelike activity in control animals following volume expansion, but no natriuretic hormonelike activity in plasma from volume-expanded rats with AV3V lesions. These data demonstrate that AV3V periventricular ablation attenuates the natriuresis induced by isotonic-volume expansion. In addition, preliminary results indicate the AV3V region may be a central site critical for natriuretic hormonelike activity and control of extracellular fluid volume.

Diuretic and cardiovascular effects of indapamide in hypertensive subjects: a dose-response curve

In a single-blind, placebo-controlled study, the effects were evaluated of increasing doses of indapamide (1.0, 2.5 and 5.0 mg/day, each dose for 4 weeks) on volume and haemodynamic status of 10 hypertensive subjects. Body weight showed a decrease of 0.5 kg at the 1 mg dose, of 1.0 kg at the 2.5 mg dose and no further decrease at 5 mg. Plasma volume did not change. Mean arterial pressure decrease in 8 subjects by about 20 mmHg; 2 patients were classified as 'non-responders'. The decrease in blood pressure was accompanied by a reduction in total peripheral resistance and no change in cardiac output. LV end-diastolic volume decreased by about 20 ml. These results suggest that indapamide not only has a diuretic effect, but also acts as a veno-arterial vasodilator.

[Experience in pair-feeding of rats treated with nitrate or sodium nitrite]

A nutritional and toxicological study has been made of rats, using the pair-feeding technique. The animals were fed a diet containing 5% of NO-3 ion or 0.5% of NO-2 ion (in the form of sodium salts). Under these conditions, a decrease was noted in the consumption of solid food which caused a net loss of weight. Besides, nitrates notably increase liquid intake and diuresis while nitrites induce a significant decrease in the protein retention coefficient.

The place of indapamide in the treatment of arterial hypertension

Clinical efficacy is not the sole criterion today in the drug treatment of hypertension, a condition which is so often asymptomatic and one which demands prolonged, usually lifetime, management of the patient. Patient compliance with treatment is essential and the practical usefulness of a drug can be determined by its side-effect liability, convenience and simplicity of administration and low possible long-term risk potential. There is growing experimental and clinical evidence that indapamide, an antihypertensive agent with only limited diuretic activity at low dosage (2.5 mg as a single dose per day), is proving to be a consistently effective and well-tolerated alternative to the thiazides and beta-blockers as a first-line treatment, and a useful addition in multi-drug regimens. Some of the recent data, particularly from U.S. and Canadian studies, are briefly reviewed.

Decreased distal acidification in acute hypercapnia in the dog

The present studies evaluate the effect of acute hypercapnia on distal nephron H+ secretion (DNH+S) in vivo by means of the urine-blood PCO2 difference (U-B PCO2) in alkaline urine. Bicarbonaturia was induced by either a sodium bicarbonate infusion or L-lysine administration. Our results demonstrate that the U-B PCO2, as a function of the urinary bicarbonate concentration, was significantly lower during acute respiratory acidosis; this effect was not dependent on changes in glomerular filtration rate and/or fractional excretion of sodium, potassium, and chloride. Infusion of the sodium salts of sulfate, a nonreabsorbable anion, did not correct the diminished U-B PCO2. Amiloride caused the U-B PCO2 to fall in normocapnic dogs but not in hypercapnic dogs. When hypercapnia was superimposed in dogs with extracellular fluid volume contraction, there were no changes in the U-B PCO2. This study indicates that acute hypercapnia in the intact dog decreases DNH+S and is compatible with an effect of hypercapnia on the voltage-dependent component of urine acidification. The mechanism appears to be direct rather than secondary to factors that influence the rate of sodium delivery to the distal nephron.

Effect of inhibitors of prostaglandin synthesis on induced diuresis in cirrhosis

The effect of inhibitors of prostaglandin synthesis on diuretic action was examined in patients with ascites due to chronic liver disease and in normal subjects. In patients with ascites, natriuresis after 80 mg i.v. furosemide was reduced 82% by pretreatment with indomethacin. Creatinine clearance was reduced only 16%. These effects were likely due to inhibition of renal prostaglandin synthesis, since urinary prostaglandin E2 fell and there was also reduction in natriuresis with naproxen (52%). The effects were not specific for furosemide since spironolactone-induced natriuresis was also reduced by indomethacin (82%), naproxen (52%), and aspirin (33%). In normal subjects, indomethacin reduced furosemide natriuresis by only 14% while creatinine clearance was not affected. The mechanisms of these drug interactions are uncertain but probably involve renal hemodynamics which appear to be supported importantly by renal prostaglandins in patients with ascites due to liver disease.

Substance P-induced changes in kidney function in the conscious rat: relation to the renal prostaglandin system

Infusion of substance P into the renal artery was previously shown to cause a significant natriuresis which was associated with increased kallikrein excretion. Since the renal kinin and prostaglandin (PG) systems may be interrelated, the present study was performed to investigate the effects of substance P on renal function and its potential interaction with the renal PG system in the conscious rat. 24 female Sprague-Dawley rats were infused intravenously with substance P (1 ng . min-1 . kg-1 body weight) and the body weight was kept constant by an intravenous infusion of 0.45% saline. Substance P had no effects on arterial blood pressure, glomerular filtration rate (GFR) and 125I-hippuran clearance in the absence or presence of indomethacin (INDO). Basal UPGE2 V was unaltered by substance P infusion but was suppressed by INDO before and during substance P by 80 and 88%, respectively. Substance P raised urinary flow rate (V) by 105%, CH2O by 96%, UNaV by 378%, UKV by 48% and UPO4V by 147% (p less than 0.001). Although INDO significantly suppressed V, CH2O, and UNaV during all collection periods, it did not affect absolute UPO4V and UKV and the relative rise in V, CH2O, and UNaV induced by substance P. Thus, the diuretic and natriuretic effects of substance P are not mediated by renal PG, but are partially blunted by INDO through increased distal absorption of sodium and water, INDO has no effect on substance P-induced alterations in proximal tubular function.

The possible mode of action of indapamide: a review

It is not clear whether indapamide reduces blood pressure by a vasodilator or a diuretic action. This review attempts to answer this fundamental question. Cardiovascular studies show small increases in cardiac output, heart rate and stroke volume with a significant reduction in peripheral resistance. Indapamide, in vitro, directly inhibits pressor stimuli probably through a reduction of calcium flux in vascular smooth muscle, whilst diuretics are inactive. In vivo studies in man also show a reduction in sensitivity to pressor doses of noradrenaline and angiotensin without an increase in adrenergic sensitivity. However, indapamide does have mild diuretic activity at therapeutic doses, as shown by changes in plasma sodium, potassium, urea, uric acid and a reduction in body weight, but the changes are appreciably less than with thiazides. These results would suggest that indapamide has both diuretic and vasodilator properties. A low urinary excretion and specific accumulation into arterial smooth muscle of this lipophilic molecule may provide a rationale for this dual activity.

The role of vasopressin suppression in phencyclidine-induced diuresis

Phencyclidine (PCP; 10 mg/kg, s.c.) produced a marked diuresis which occurred without significant changes in solute excretion. This diuresis occurred predominantly within 2 h of PCP injection, and was blocked by pretreatment with vasopressin. The maximum diuresis corresponded temporally to a significant fall in plasma vasopressin and rise in mean arterial pressure. Thus, PCP-induced diuresis is due, at least in part, to suppression of plasma vasopressin. This suppression is probably related to the rise in blood pressure, though direct effects of PCP on the neurohypophysis cannot be excluded.

Morphometric, biochemical, and physiological assessment of perinatally induced renal dysfunction

Three chemicals, known either to alter renal development when administered during fetal development or to affect renal function when administered to adult rats, were administered to Sprague-Dawley rats at critical periods of renal development. Chlorambucil (CHL) was administered ip on d 11 of gestation at doses of 0, 3, and 6 mg/kg; nitrofen (2,4-dichlorophenyl p-nitrophenyl ether) (NIT) was given po on d 8-16 of gestation at 0, 4.17, 12.5, and 25 mg/kg . d; and mercuric chloride (MER) was given sc on postnatal d 1 at 0, 14, and 28 micrograms/pup. To assess the effects of these toxicants on the functional development of the kidneys, a diuresis test with and without antidiuretic hormone was applied on postnatal d 3 (PD 3); a hydropenia test on PD 6; and kidney weights, glomerular counts in midhilar cross sections, and the specific activity of renal alkaline phosphatase were determined on PD 3 and 6. Data from pups with obvious malformations of the kidneys was eliminated from the statistical analyses of the data so that emphasis could be placed on alterations of functional development in individuals with apparently morphologically normal kidneys. CHL retarded the growth and biochemical differentiation of the kidney at 6 mg/kg. Pups from this treatment groups showed an attenuated response to exogenously administered antidiuretic hormone. NIT impaired growth and altered renal morphology at a dose of 12.5 mg/kg . d and altered physiological responses in the absence of anatomical changes at a dose of 4.17 mg/kg . d. MER, at doses near the maximum tolerated, failed to alter any parameter, indicating that the very young animal differs markedly from the adult in response to that compound. The data indicate that relatively simple tests of renal function are useful in the detection of perinatally induced nephrotoxicity.

Slow rise and diurnal change of blood pressure with saralasin and angiotensin II in rats

Our objectives were to determine whether saralasin, like angiotensin II, raises blood pressure gradually when given by constant infusion and whether either agent alters the diurnal variation of arterial pressure. Eight female Wistar rats were infused intravenously with 5% dextrose for 2 days, then with saralasin at 10 micrograms . kg-1 . min-1 for 4 days, and finally with dextrose for 2 days. Six other rats were infused with angiotensin II (20 ng . kg-1 . min-1) instead of saralasin. Mean arterial pressure (MAP) was recorded continuously. Saralasin and angiotensin II gradually raised MAP in all rats, by 22.0 mmHg on the 4th day of saralasin and by 41.7 mmHg on the 4th day of angiotensin II. Both agents also increased the diurnal variation of blood pressure, MAP increasing 8.3-20.6 mmHg during the night and falling 6.7-19.1 mmHg during the day. Variability of arterial pressure was also increased by saralasin and in an earlier experiment by angiotensin II. We conclude that saralasin has a slow pressor action similar to that of angiotensin II but distinct in its timing both from the rapid agonist action of saralasin and from the acute vasoconstrictor action of angiotensin II. These effects of saralasin may compromise interpretation of experiments in which the drug is given by prolonged infusion to assess the role of angiotensin II.

Diuretic effect of slow-release furosemide in elderly patients

To compare the natriuretic and diuretic effects of a slow-release and a standard formulation of furosemide, 18 elderly patients with stable congestive heart failure were hospitalized and treated with one of these formulations in a double blind randomized trial. Patients received placebo on the first 2 days, furosemide on the third day and placebo again on the last 2 days of the study. In patients receiving the standard formulation mean urine output was increased only on the day of active treatment. However, in patients who had received the slow-release preparation, increased urine excretion was seen both on the day of active treatment and on the subsequent day. The total diuresis (0-48 h) in the 2 groups was equal, but a peak diuresis (0-6 h) was seen only in patients on the standard formulation of furosemide. Sodium excretion followed the pattern of urine excretion. Furosemide in a slow-release formulation offers advantages in maintenance therapy in congestive heart failure, especially in elderly patients.

Antidiuresis and decreased sodium excretion during cyclo-oxygenase inhibition in the conscious dog

Studies were undertaken to further elucidate the role of endogenous prostaglandins in normal renal function in the awake dog. Meclofenamate (2 mg/kg and 2 mg/kg/h, i.v.) was administered after control measurements. Parallel time control experiments were also performed. Inhibition of renal prostaglandin synthesis was documented by significant reduction in urinary prostaglandin E2 excretion rate. Urine flow and sodium excretion were reduced by meclofenamate infusion. In addition, fractional excretion of sodium was reduced, implying enhanced sodium reabsorption during prostaglandin synthesis inhibition. Renal hemodynamics, glomerular filtration and systemic hemodynamics were unaffected. It is concluded that endogenous prostaglandin release is important in influencing sodium and water excretion in the conscious dog.

Effects of a nonpressor analogue of vasopressin on plasma renin activity and salt and water excretion in water-loaded, anesthetized dogs

The object of this study was to determine the importance of vasoconstrictor activity in the suppression of renin secretion by vasopressin. Arginine vasopressin (AVP) (0.05 and 0.1 ng/kg/min) and a nonpressor analogue of vasopressin, 1-deamino-[4-threonine, 8-D-arginine]-vasopressin (dTDAVP) (0.01 and 0.05 ng/kg/min), were infused intravenously in anesthetized hypophysectomized dogs. Neither dTDAVP nor AVP influenced arterial pressure or heart rate but both suppressed plasma renin activity. Infusion of dTDAVP at 0.01 and 0.05 ng/kg/min suppressed plasma renin activity to 86 +/- 4% (p less than 0.05) and 63 +/- 6% (p less than 0.01) of the control values respectively. Infusion of AVP at 0.05 and 0.1 ng/kg/min suppressed plasma renin activity to 60 +/- 8% (p less than 0.01) and 59 +/- 12% (p less than 0.05) of the control values respectively. dTDAVP and AVP both produced significant increases in sodium excretion. These data demonstrate that vasoconstrictor activity is not required for the effects of vasopressin on renin secretion and sodium excretion.

Hyponatremic disorders due to vasopressin excess

Vasopressin is capable of being stimulated by several nonosmotic factors such as hypovolemia, hypotension, pharmacologic agents and stress. Vasopressin levels of only 1-2 pg/ml are capable of decreasing substantially renal water excretion. If water is ingested or given intravenously in this setting, positive water balance with hypotonicity and hyponatremia of extracellular fluid (ECF) occur. Such dilution of the ECF results in water movement into cells and potential central nervous system complications [3]. Many disorders (see Tab. 1) may be associated with nonosmotic stimulation of vasopressin release. In these clinical settings, judicious administration of free water and monitoring of serum sodium concentration is necessary. A knowledge of clinical conditions associated with vasopressin-mediated water retention may have therapeutic implications as well. Thus, in recent years it has become appreciated that selected pharmacologic agents such as lithium and demeclocycline can impair the water retaining property of vasopressin [26]. Although lithium appears too toxic for routine usage, demeclocycline has proved to be efficacious therapy in some patients with high vasopressin levels and hyponatremia due to the syndrome of inappropriate secretion of antidiuretic hormone who are unable to limit their water intake [9]. More recently, other compounds that selectively antagonize the hydro-osmotic effect of vasopressin are being tested and soon may be available [13].

Dysfunction of the proximal tubule underlies maleic acid-induced type II renal tubular acidosis

To investigate whether dysfunction of the proximal tubule underlies maleic acid-(MA) induced type II ("proximal") renal tubular acidosis (RTA II), we intravenously administered either MA or acetazolamide to eight conscious trained dogs undergoing water diuresis and examined the relationship between fractional solute-free water clearance (Ch2o/GFR), a measure of NaCl reabsorption in the post-proximal nephron, and either fractional urine flow (V/GFR), a measure of total solute rejected by the proximal tubule, or the sum of fractional excretion of Cl- and Ch2o/GFR [(Ccl + Ch2o)/GFR], a measure of proximally rejected solute that is potentially reabsorbable by the thick ascending limb. When MA or acetazolamide induced brisk bicarbonaturia at normal plasma bicarbonate concentrations: 1) V/GFR, (Ccl + Ch20)GFR, and Ch2o/GFR increased strikingly; 2) at any increment of Ch2o/GFR ws not; 3) the increments of V/GFR correlated positively with those of fractional excretion of bicarbonate (P less than 0.001); 4) during hyperchloremic acidosis, MA-induced bicarbonaturia was greatly attenuated; the increment in V/GFR was halved and approximated that in Ch20/GFR, which was unchanged; 5) when plasma bicarbonate was abruptly increased, bicarbonaturia increased strikingly and V/GFR increased further but Ch20/GFR and aminoaciduria did not. We conclude that MA induces a reduction in the net rate at which the proximal tubule reabsorbs HCO-3, Na+, and Cl-. This dysfunction underlies RTA II and evokes greatly increased reabsorption of Cl- and Na+ in the post-proximal tubule.

Renal autotransplantation in sheep--preparation and physiology

A novel procedure for renal autotransplantation in sheep is described. The operative procedure involved two preliminary operations for preparation of carotid artery and jugular vein loops and of a Wright-type parotid fistula. At transplantation the renal artery and vein were anastomosed end-to-end to carotid artery and jugular vein and the ureter was anastomosed end-to-end to the parotid duct. The cranial ends of the carotid artery, jugular vein and parotid duct were ligated and the parotid gland was denervated. The remaining abdominal kidney was removed 2 days after transplantation. Over periods now as long as 36 months, glomerular filtration rate was 24.1 +/- 0.7 ml/min and effective renal plasma flow was 204 +/- 6 ml/min (73 determinations in 7 sheep), compared to values of 48 +/- 4 and 305 +/- 26 ml/min previously reported for sheep with both kidneys in situ. The physiological response of the kidneys to water load and deprivation, arginine-vasopressin injection, intravenous hypertonic sodium load and 24 h sodium depletion have been examined and show the transplanted kidneys responded in the appropriate manner. Maximum urine osmolality of up to 1000 mOsmol/kg was observed after 24 h water deprivation, and minimum osmolality of 108 +/- 25 mOsmol/kg was observed after administration of 75 ml/kg oral water load. Fractional sodium reabsorption was greater than 99.9% after 24 h sodium depletion, whilst it fell to 92.5 +/- 0.5% after intravenous administration of a hypertonic NaCl load. All these values are in the same range as observed for normal sheep following similar treatment. This preparation provides a sole kidney with immediate access to its blood vessels and secretions for physiological and pharmacological research.

Renal Na+-K+-ATPase in renin release

The effects of ouabain and furosemide on renin secretion, renal function, and renal Na+-K+-ATPase were investigated in anesthetized dogs. Furosemide (2 mg/kg) induced significant diuresis, natriuresis, an increase in renal blood flow (RBF), and a fivefold increase in renin secretory rate (RSR), but no changes in glomerular filtration rate (GFR). Infusion of ouabain (1 microgram . kg-1 . min-1) into one renal artery during furosemide diuresis increased fractional sodium excretion from 22 +/- 2 to 30 +/- 3% from the ipsilateral kidney but did not change urine flow, RBF, or GFR, whereas RSR fell to control values (698 +/- 203 to 137 +/- 43). When ouabain preceded furosemide, the rise in RBF and RSR induced by furosemide was abolished but sodium excretion increased. Ouabain infused in vivo inhibited Na+-K+-ATPase in microsomal fractions from cortex (34%) and medulla (27%) as compared with control. Neither saline nor furosemide exerted any effect on Na+-K+-ATPase. Moreover, the effect of ouabain alone on Na+-K+-ATPase was not different from that of ouabain plus furosemide. No changes in Mg2+-ATPase were detected in any of the experiments. These results indicate that inhibition of renal Na+-K+-ATPase abolishes furosemide-induced renin secretion despite potentiation of the natriuretic effect of the diuretic. It is apparent that the level of activity of Na+-K+-ATPase is of prime importance for renin secretion. In addition, ouabain may act directly on the juxtaglomerular cells to inhibit renin secretion.