Cyclic AMP in urine, kidney and liver following long-term administration of fluoride to rats

Rats were exposed to fluoride (F) for up to 8 weeks through the drinking water containing 100 p.p.m. F. Urine samples were regularly collected, together with tissue samples of liver and kidney at termination. All samples were assayed for cyclic AMP. No F-effect was found on liver or kidney levels of cyclic AMP. In the urine from the F-exposed rats there was an overall increase in the cyclic AMP concentration, but a decreased or unaffected 24 hrs urinary excretion of cyclic AMP. However, the F-exposed rats exhibited a considerably lower diuresis than the control animals. Because a significant negative correlation was found between diuresis and urinary concentration of cyclic AMP, the material was corrected to similarity in the mean diuresis between the two groups. Then no effect of F-exposure could be detected either in the urinary concentration or the daily excretion of cyclic AMP.

Synthesis and some pharmacological properties of oxytocin and vasopressin analogues with sarcosine or N-methyl-L-alanine in position 7

Eight analogues of oxytocin and arginine-vasopressin were synthesized, in which the proline residue in position 7 was replaced by either sarcosine or N-methylalanine; some of the pharmacological properties of these analogues were evaluated. In peptides containing a beta-mercaptopropionic acid residue in position 1, the additivity of the effects of deletion of the amino group in position 1 and of the above-noted replacements in position 7 on biological properties of these analogues was ascertained. All of the analogues were found to be potent in either antidiuretic or uterine activity and also selective in action. From the point of view of pharmacological properties, substitution of sarcosine in position 7 of oxytocin gave analogues with higher oxytocic and milk-ejecting activities than did the substitution of N-methylalanine. The opposite structure-activity relationship was observed with arginine-vasopressin, where the N-methylalanine-containing analogues were more potent than the sarcosine-containing analogues with respect to pressor activity and also, if not deaminated, with respect to antidiuretic activity.

The effect of dietary sodium and protein on urine volume and water intake

To test the notion that water intake and urine volume are related to dietary sodium or protein intake in free-living persons, we studied normal men at three levels of sodium intake and two levels of protein intake. Twenty-four men received 10, 200, and 400 mEq/day sodium intake for 7 days while protein and caloric intake were maintained constant. Eight men received 80 or 180 gm/day protein intake for 7 days while caloric and sodium intake were maintained constant. Although sodium, solute, and urea nitrogen excretion changed appropriately according to the regimens, there was no demonstrable influence of sodium or protein intake on water intake and urine volume. We conclude that in normal free-living American man, water consumption is independent of either sodium or protein intake.

Furosemide and mannitol in the treatment of acute experimental intracranial hypertension

Intracranial hypertension was induced in dogs and a small number of baboons by the inflation of epidural balloons. The resulting increased intracranial pressure (ICP) was treated with standard clinical doses of furosemide (0.7 mg/kg), "mini" doses of mannitol (0.75 g/kg), or both agents in combination. Mannitol consistently and rapidly reduced ICP in all animals. When results were averaged, furosemide used alone caused a slow reduction in ICP, but the results were variable in individual animals--with ICP actually increased in some. When furosemide and mannitol were given together, the ICP fell rapidly and remained low for considerably longer than after either agent alone.

2-(Aminomethyl)phenols, a new class of saluretic agents. 5. Fused-ring analogues

A number of bicyclic ring-fused analogues of 2-(aminomethyl)phenol were synthesized and tested orally in rats and intravenously in dogs for saluretic and diuretic effects. Of the 15 alicylic, aromatic, and heterocyclic ring-fused compounds tested, only 2-(aminomethyl)-4-chloro-1-naphthalenol hydrochloride (2) and 7-(aminomethyl)-6-hydroxy-5,8-dimethyl-1,2,3,4-tetrahydronaphthalene hydrochloride (6) displayed a high order of activity.

The mechanism of polyuria in rats pretreated with lithium studies by in vitro microperfusion

The collecting ducts in papillae taken from normal rats have a measurable increase in diffusional tritiated water (THO) permeability with ADH 5 mu unit/ml and this increase is maximal with antidiuretic hormone (ADH) 100 mu unit/ml added to media. The presence of plasma from rats pretreated with lithium to make them polyuric inhibited the response to ADH. The lowest concentration of ADH that caused a measurable increase in diffusional water permeability was 50 mu unit/ml and the increase was maximal with ADH 2000 mu unit/ml. The maximum response to ADH did not differ whether plasma from control or lithium pretreated rats was used. However, the dose-response curve to ADH was shifted to the right by the plasma from lithium-pretreated rats. Lithium added to the plasma from control rats did not alter the response to ADH. It is proposed that lithium given to rats causes a circulatory factor to be produced that inhibits in a competitive fashion the response of the collecting duct to ADH. Such an effect would explain many features of the impairment of water excretion associated with lithium use.

Effect of chronic salt loading on renal Na-K-ATPase activity in the rat

The effect of chronic salt loading in rats fed regular chow diet on renal Na-K-ATPase was studied. The high salt intake was associated with increased filtered load of sodium (control: 126 +/- 3.9 mueq/min, salt loaded: 146 +/- 2.5, mueq/min, P less than 0.001), increased net reabsorption of sodium (control: 125.3 +/- 3.9 mueq/min, salt load: 134.8 +/- 2.4 mueq/min, P less than 0.05), increased urinary excretion of potassium (control: 2.4 +/- 0.09 mueq/min/min; salt loaded: 3.0 +/- 0.1 mueq/min, P less than 0.001) and increase in single kidney weight (control: 0.798 +/- 0.010 g, salt loaded: 0.937 +/- 0.015 g, P less than 0.001). The above mentioned changes were associated with significant increase in renal microsomal and whole homogenate medullary Na-K-ATPase activity in the salt loaded group (microsomes: control 74.1 +/- 4.9 mumole Pi/mg prot/hr, salt loaded 112.7 +/- 6.0 mumole Pi/mg prot/hr, P less than 0.001; whole homogenate: control 22.7 +/- 1.0 mumole Pi/mg prot/hr, salt load 29.4 +/- 1.6 mumole Pi/mg prot/hr, P less than 0.005), while cortical and papillary Na-K-ATPase activity remained unchanged. Taken together, these results show that increased filtered and reabsorbed load of sodium, which follows high salt intake, is associated with an increased renal Na-K-ATPase activity. The preferential rise in medullary enzymatic activity may be interpreted as suggesting that these changes may stem from increased delivery and reabsorption of sodium in the ascending limb of Henle's loop.

[Use of antipotassiuretic diuretic amiloride in patients with chronic cardiac failure]

Amyloride causes moderate natriuresis and a considerable reduction in urinary potassium excretion. Chlorine excretion and diuresis are less affected in their increase, while hydrogen ions secretion shows a slight decrease. Amyloride effect is localized in convoluted tubules of the kidney, and perhaps collecting tubules as well. When taken orally, its effect becomes evident within 2-3 hours, reaches its peak within 5-6 hours, and slowly declines within 16-18 hours. A daily dose of 10-15 mg is recommended. During a treatment course, the effect is in evidence throughout the whole of the 6-8 days of observation, without any signs of hyperpotassemia or shifts in acid-base balance. Amyloride combined with furosemide, uregit or hypothiazid produces an additive effect on natriuresis and essentially reduces renal loss of potassium and hydrogen ions.

Inhibition of mitochondrial function is not the diuretic mechanism of ethacrynic acid in the dog

Kidney metabolites were studied in five anesthetized dogs before and after 5 mg/kg i.v. of ethacrynic acid, followed by 3 mg X kg-1 X hr-1. This dose, which inhibits most of the reabsorption of sodium and chloride in the diluting segment, improved the energy state in biopsies from the outer medulla and caused an increase in ATP and a decrease in ADP and AMP levels and the lactate/pyruvate ratio. This was probably related to ongoing rapid metabolism in the control biopsies (with improved results after ethacrynic acid due to a primary reduction in an ATP requiring process) before they were completely frozen in liquid nitrogen. No changes occurred in ATP, ADP or phosphocreatine levels or the lactate/pyruvate ratio in cortical biopsies, which was in agreement with the previously shown lack of effect on proximal tubular reabsorption at this dosage of ethacrynic acid. These results indicate that the saluretic effect and parallel reduction in outer medullary metabolic rate with ethacrynic acid cannot be due to a direct inhibition of mitochondrial ATP production as suggested by others from in vitro experiments. The reduced rate of ATP production in vivo must be secondary to a reduced ATP demand.

An attempt to quantitate the contribution of antidiuretic hormone to the diuresis of left atrial distension in conscious dogs

In order to quantitate the contribution of the antidiuretic hormone (ADH) to the diuresis of left atrial distension 52 experiments have been performed in 12 conscious, chronically instrumented beagle dogs. Left atrial pressure was increased by a reversible mitral stenosis by about 10 cm H2O (1.0 kPa) for 60 min. Plasma ADH concentration (range between 1.3 and 6.0 pg . ml-1) (radioimmunoassay) decreased in every experiment, the average decrease being about 50%. An i.v. infusion of vasopressin (0.05 mU . min-1 . kg-1) abolished the diuretic effect of left atrial distension or decreased the urine volume below control values; natriuresis was not affected. The magnitude of the vasopressin effect was dependent on the concurrent sodium excretion: when sodium excretion was low during left atrial distension, vasopressin was more effective in reducing the urine volume than when sodium excretion was high. It is concluded that the diuresis of left atrial distension is mediated (a) by a suppression of ADH and (b) by factors controlling sodium excretion, the contribution of these two mechanisms being dependent on the concurrent sodium excretion.

Determinants of bumetanide response in the dog: effect of probenecid

The pharmacokinetics and pharmacodynamics of intravenous bumetanide (0.250 mg/kg), alone (treatment I) and after probenecid pretreatment (treatment II), were studied in four mongrel dogs. Lactated Ringer's solution was administered by vein throughout both treatments at a flow rate of 2 ml/min to avoid fluid and electrolyte depletion. Bumetanide and probenecid concentrations were analyzed by HPLC, sodium by flame photometry, and creatinine by colorimetry. Although the probenecid markedly reduced the plasma and renal clearances of bumetanide, as well as the fraction excreted unchanged in the urine, there was no significant difference between treatments I and II in the 4-hr natriuretic and diuretic responses. However, analysis of the dose-response curves between treatments I and II showed that sodium excretion was better correlated with bumetanide urinary excretion rate than with plasma concentration. The reasons for a poor correlation between treatments during the early time periods are discussed.

Acetylsalicylic acid suppresses the renal hemodynamic effect and reduces the diuretic action of furosemide in cirrhosis with ascites

To investigate if lysine acetylsalicylate influences the hemodynamic and diuretic responses to furosemide in cirrhosis, 21 nonazotemic patients with ascites were studied. In 8 patients (group 1), the renal plasma flow and glomerular filtration rate were serially measured before and during three 30-min periods after the i.v. administration of lysine acetylsalicylate (450 mg). In 7 patients (group 2), renal plasma flow, glomerular filtration rate, urine volume, and sodium excretion were measured before and during three 20-min periods after the i.v. administration of furosemide (40 mg). After a 45-min period in which urinary losses were restored, a similar study was performed before and after a second injection of furosemide (40 mg). Six patients (group 3) were studied with an identical protocol as group 2, except that the second injection of furosemide was preceded by the administration of lysine acetylsalicylate (450 mg). In 6 patients of group 1, lysine acetylsalicylate caused a marked and reversible reduction of renal plasma flow and glomerular filtration rate. In groups 2 and 3, the i.v. injections of furosemide alone produced a significant increase in renal plasma flow and glomerular filtration rate, and a marked diuresis and natriuresis. In patients of group 3, pretreatment with lysine acetylsalicylate suppressed the renal hemodynamic effect and markedly reduced the diuretic effect of the second injection of furosemide. Lysine acetylsalicylate did not cause the appearance of renal insufficiency in any of these patients. These results suggest that prostaglandins are involved in the renal response to furosemide in cirrhosis with ascites and that furosemide protects these patients from developing renal insufficiency after acute administration of nonsteroidal antiinflammatory agents.

Angiotensin II and bradykinin: interactions between two centrally active peptides

Two neuropeptides, bradykinin (BK) and angiotensin II (ANG II), produce an increase in blood pressure when injected into the brain ventricles. This study is an example of central peptide-peptide interaction and was carried out to determine if BK and ANG II share a common mechanism in the brain to control blood pressure and drinking in rats. Prior injection of saralasin [10 micrograms intraventricularly (ivt)] was found to enhance the pressor response to ivt BK (5 micrograms) by 44%. The same dose of saralasin attenuated the pressor response to ivt ANG II (200 ng) by 55%. 50 ng ANG II and 5 micrograms BK given together ivt did not significantly alter blood pressure or urine conductance compared to 50 ng ANG II alone. Drinking to ivt infusions of ANG II (14 ng/min) was significantly attenuated when combined with BK (0.7 micrograms or 2.8 micrograms/min). Pretreatment with 10 micrograms indomethacin ivt diminished the pressor response to 5 micrograms ivt BK. Prostaglandin E2 (1.4 micrograms/min), but not prostaglandin A2, inhibited drinking to 14 ng/min ivt infusions of ANG II. The results suggest that ANG II and BK share an interrelationship with respect to their central actions: ANG II inhibits the BK pressor response and BK acts to inhibit drinking induced by ANG II. Prostaglandins of the E series may mediate these central actions of bradykinins.

[Artificial blood. Experimental studies on fluorocarbons as chemical blood substitutes]

Fluorocarbonates are organic compounds capable of carrying oxygen and surrendering it to tissues by means of biological sound modalities. Experimentation of an emulsion consisting of perfluorotripropylamine and perfluorodecaline (Fluosol DA 20%) as a blood substitute is reported. Acute (Ht less than 1%) and chronic morphological (Ht = 15%) studies were performed on rats, and a semi-acute biochemical and morphological protocol (Ht = 21%) was experimented in pigs. The first signs of altered cerebral electrical activity occurred at Ht = 2% in the acute experiments, and death due to respiratory arrest took pace at Ht = 0.5%. In the semiacute and chronic experiments, widespread infiltration of fluorocarbonic micelles was noted on histological and electron microscope lung and liver preparations.

Pharmacological studies with beclobrate, a new hypolipidemic agent

A new diphenylmethane derivative with potent hypolipidemic activity, ethyl-(+/-)-2-[[alpha-(p-chlorophenyl)-p-tolyl]-oxy]-2-methylbutyrate (Sgd 24774, beclobrate) has been investigated in animals. From a comparison of the ED25 values of beclobrate and clofibrate, the new drug is 11 times more potent with respect to its hypocholesterolemic activity and 36 times more hypotriglyceridemic in normally fed rats, and lowers fructose-induced hypertriglyceridemia in rats 20 times as effectively as does clofibrate. On a similar basis of comparison, the hepatomegalic effect of beclobrate in rats is 22 times that of clofibrate. High doses of beclobrate did not reveal any other peripheral or central effects in a wide range of pharmacological tests, indicating a high specificity of the action of the drug on blood lipids. On the basis of the results of interaction studies performed with beclobrate in animals, administration of the substance in man should be largely free from risk.

Inhibition of prostaglandin synthesis and the action of vasopressin during extracellular volume expansion in the dog

The increased renal sodium and water excretion after an intravenous infusion of Ringer solution has been investigated in anaesthetized dogs. The response of the kidneys has been examined in four combinations. The functional parameters of renal function have been compared during volume expansion by 1.5-2.0% body weight Ringer solution and overhydration by 2.5% Ringer solution for 60 min. In the control animals, volume expansion by 2% body weight Ringer solution resulted in a significant increase in sodium excretion and urine flow. When these animals were infused with 2.5% body weight Ringer solution a marked increase in water excretion was observed with a smaller increment in sodium excretion, and the urine became hypo-osmotic as compared to the plasma. No difference was found in glomerular filtration rate and PAH clearance. In the group No. 2, the effect of 4 mg/kg indomethacin infusion was studied. The inhibition of prostaglandin synthesis considerably reduced the diuretic effect of Ringer infusion and did not affect sodium excretion. In the group No. 3, the animals received lysine-8-vasopressin i.v. in a preliminary dose of 10 mU/kg during 10 min and then 50 mU/kg over 60 min in infusion. Volume expansion with 2.5% body weight of Ringer solution resulted in a marked increase in sodium and water excretion but no difference was found in glomerular filtration rate and PAH clearance. Dilution of the urine i.e. a decrease of urinary osmolarity, in spite of the vasopressin infusion, was significantly higher in this group than in the control animals (group No. 1). In the fourth series, after 4 mg/kg of indomethacin the same dose of vasopressin was administered as in group No. 3. Indomethacin was observed to inhibit the diuretic effect of vasopressin and did not affect the saluretic effect. From these data it was concluded that medullary tonicity affected renal water handling during extracellular isosmotic hypervolaemia induced by Ringer infusion. This mechanism depends on medullary prostaglandin synthesis and is independent from the plasma vasopressin concentration. Our findings clearly indicate that extracellular hypervolaemia increases renal sodium excretion and lysine-8-vasopressin was found to potentiate this effect. This sodium excretion increasing mechanism does not depend on renal prostaglandin secretion, nor were glomerular factors responsible for the increase of sodium and water excretion.

Eating, drinking and urine output after prolonged cerebroventricular vasopressin infusions in rats

Prior studies suggested that centrally administered single doses of vasopressin (VP) do not affect consummatory behavior or peripheral hydration. To reduce uncertainties related to factors of unknown distribution, concentration and duration, we infused VP (0.5 or 50 ng/h) continuously for 5 h or 5 days into a lateral cerebroventricle of conscious male rats. Eating and drinking behavior, as well as urine volume and sodium and potassium output, were unaffected by these treatments. The results suggest that VP, at sites reached from cerebrospinal fluid, does not alter peripheral hydration of rats.