Cyanide poisoning: pathophysiology and current approaches to therapy

Considering the difficulties following the administration of nitrites (or aminophenols) or cobalt-EDTA as well as the ineffectivenes of hydroxycobalamin and pyruvate, we feel that a more sensible treatment for acute cyanide intoxication is hemodialysis combined with the intravenous administration of sodium thiosulfate. The addition of hemodialysis to such a regimen is helpful in three ways. First, it removes the small extracellular reservoir of cyanide, particularly if the poison is still being absorbed from the gastrointestinal tract. Second, it corrects the severe lactic acidosis seen in virtually all cases of cyanide toxicity. As with most poisons death from metabolic acidosis alone is likely. Third, the removal of thiocyanate, the end product of cyanide metabolism, results in a maneuver which should decrease both tissue and plasma cyanide levels. The immediate treatment of acute cyanide intoxication is supportive, as it is with most all drugs and poisons. Gastric lavage using activated charcoal should be initiated immediately to remove any remaining cyanide in the gastrointestinal tract. Simultaneously, high flow oxygen should be administered either by nasal cannula or by endotracheal intubation. Correction of the metabolic acidosis should be instituted with bicarbonate. Immediate hemodialysis should be performed with the concomitant administration of thiosulfate. Animal studies suggest that continuous infusion of thiosulfate (12 mg/kg/hr) is more effective for treating cyanide intoxication than is bolus administration (41, 51). Bolus administration is the currently recommended form of thiosulfate therapy in humans. The Lilly kit contains a 50 ml ampule of thiosulfate having 12.5 gm, which in adults may be repeated once at one-half the dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Dimethyl sulfoxide affects water flow through a nonosmolar action

Dimethyl sulfoxide (DMSO) is a dipolar organic compound commonly used as a solvent in studies of membrane transport. DMSO also has many effects on cell function and, although the precise mechanism of action is not known completely, it has been stated to exert its effect on transport solely through osmolality. The present study was designed to examine the effects of serosal DMSO at three osmolar concentrations on Basal Water Flow and vasopressin (AVP)- and cyclic AMP-stimulated water flow (Maximal Water Flow) in the toad bladder. The results obtained were compared to equi-osmolar concentrations of mannitol and NaCl. All three agents significantly enhanced Basal Water Flow after 60 min. The results obtained on Maximal Water Flow were different depending on the final osmolality. At 300 mOsm final concentration, all three agents increased AVP-stimulated water flow. When the serosal osmolality was 600 or 900 mOsm DMSO increased Maximal Water Flow, whereas mannitol and NaCl decreased it. When 300 mOsm DMSO plus 300 mOsm mannitol (600 mOsm total)-treated hemibladders were challenged with AVP, the water flow response was similar to that of 600 mOsm DMSO alone. In the presence of verapamil, AVP-stimulated water flow was decreased markedly; when DMSO was added to verapamil-pretreated hemibladders, and they were then challenged with AVP, water flow increased significantly. In similar experiments with mannitol, water flow remained inhibited. Dimethylsulfone did not enhance AVP-stimulated water flow as compared to the same concentration of DMSO. These results demonstrate that the effects of DMSO on water transport are not mediated solely by its osmolar action.(ABSTRACT TRUNCATED AT 250 WORDS)

Production of antibodies against the coenzyme pyrrolequinoline quinone

Polyclonal antibodies against pyrrolequinoline quinone have been elicited in rabbits. These antibodies react with free and protein-bound pyrrolequinoline quinone. In particular they react with native and denatured lentil seedling amine oxidase as detected by dot-blot and ELISA assays. The presence of 1 mol pyrrolequinoline quinone per mol of enzyme was determined by the last method.

Spectroscopic studies of the reaction between bovine serum amine oxidase (copper-containing) and some hydrazides and hydrazines

The carbonyl cofactor of bovine serum amine oxidase, recently identified as pyrroloquinoline quinone [Ameyama, Hayashi, Matsushita, Shinagawa & Adachi (1984) Agric. Biol. Chem. 48, 561-565; Lobenstein-Verbeek, Jongejan, Frank & Duine (1984) FEBS Lett. 170, 305-309], reacts stoichiometrically and irreversibly with hydrazides of phenylacetic acid and of benzoic acid. With the phenylacetic hydrazides a reversible intermediate step was detected by competition with substrate, carbonylic reagents or phenylhydrazine, a typical inhibitor of the enzyme. All hydrazides form an intense broad band with maximum absorbance in a narrow wavelength range (350-360 nm), irrespective of the acyl group, suggesting that the transition is located on the organic cofactor. A different situation is found with some phenylhydrazines, where extended conjugation can occur between the cofactor and the phenyl pi-electron system via the azo group, as shown by the lower energy and higher intensity of the transition. In this case the transition is sensitive to substituents in the phenyl ring. The c.d. spectrum of the adducts is influenced by the type of hydrazide (derived from phenylacetic acid or benzoic acid), by pH and by NN-diethyldithiocarbamate binding to copper, probably as a result of shifts of equilibria between hydrazone-azo tautomers.

Thiazides stimulate calcium absorption in the turtle bladder

The mechanism of action of the thiazide diuretics on calcium transport is not completely understood. The present study was designed to examine the effect of hydrochlorothiazide (HTZ) on Na transport, proton secretion, and Ca45 flux in the turtle bladder, a high resistance membrane. When added to the mucosal solution, 1 mM HTZ had no effect on Na transport or proton secretion, but significantly increased mucosa-to-serosa Ca45 flux at 60 minutes (control 118.9 +/- 39.7 pmol/mg/60 min versus thiazide 286.0 +/- 64.9 pmol/mg/60 min, N = 16, P less than 0.02). In the presence of 5 X 10(-4) M ouabain, a maneuver which inhibits active Na transport, HTZ again significantly enhanced mucosa-to-serosa Ca45 flux. The increment of calcium transport under these conditions was 83.4 +/- 35.2 pmol/mg/60 min (N = 8, P less than 0.05). Mucosal HTZ had no effect on serosa-to-mucosa (that is, bath-to-lumen) Ca45 flux after a 60 minute incubation. Serosal addition of HTZ had no effect on either of the unidirectional Ca45 fluxes or on Na transport. Mucosal tissue Ca45 content was enhanced by HTZ (mucosal) in the presence or absence of ouabain. These results provide support for the view that thiazides have a direct stimulatory effect on calcium absorption at the luminal membrane, perhaps secondary to increased mucosal calcium permeability.

Inhibition of copper-dependent amine oxidases by some hydrazides of pyrrol-1-ylbenzoic and pyrrol-1-ylphenylacetic acids

Some hydrazides of pyrrol-1-ylbenzoic and pyrrol-1-ylphenylacetic acids were prepared, and their effect on copper-dependent amine oxidases (Cu-AOs) and FAD monoamine oxidases (MAOs) activities was tested. The compounds were not substrates for Cu-AO enzymes but acted as noncompetitive inhibitors. Hydrazides of pyrrol-1-ylphenylacetic acids were highly specific for plasma amine oxidase (Ki = 0.5-1 microM). In contrast, all the hydrazides were weak inhibitors of MAO activity. Incubation with the hydrazide derivatives led to irreversible inactivation of Cu-AOs. Therefore, the inhibition implied two distinct steps. The first one consisted of the rapid formation of the enzyme-inhibitor complex and was reversed by dialysis. In the second step, the complex was irreversibly transformed, probably by the formation of a Schiff base between the hydrazide and the prosthetic carbonyl group of the enzyme.

On the mechanism of toluene-induced renal tubular acidosis

This study was aimed to investigate the pathogenesis of toluene-induced renal tubular acidosis (RTA). In 5 individuals addicted to toluene sniffing we documented the occurrence of hypokalemia and hyperchloremic metabolic acidosis associated with inability to lower urine pH below 5.5 (6.06 +/- 0.24). Overall kidney bicarbonate reabsorption was normal or enhanced, a feature characteristic of the distal form of RTA (DRTA). These findings resemble those found during the administration of amphotericin B, a drug felt to cause DRTA by increasing hydrogen ion (H+) back-diffusion in the collecting tubule. In toluene sniffers, the urine pCO2 measured in a highly alkaline urine was reduced (47 +/- 8.8 mm Hg), suggesting a decrease in the rate of collecting tubule H+ secretion rather than H+ back-diffusion. To investigate these two mechanisms of altered distal acidification more directly we studied the effect of toluene on acidification by the urinary turtle bladder, an epithelial analogue of the mammalian collecting tubule. In this preparation, toluene resulted in a decrease in the rate of H+ secretion measured by either the pH stat technique or the reverse short circuit current. When mucosal pH was progressively lowered to examine H+ secretion against an H+ gradient, toluene-treated bladders displayed a significant decrease in proton conductance but the lowest mucosal pH required to nullify H+ secretion, (MpH) JH = O, was not different from that of control bladders (4.05 +/- 0.29 and 3.90 +/- 0.13, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium transport in turtle bladder

Unidirectional 45Ca fluxes were measured in the turtle bladder under open-circuit and short-circuit conditions. In the open-circuited state net calcium flux (JnetCa) was secretory (serosa to mucosa) and was 388.3 +/- 84.5 pmol.mg-1.h-1 (n = 20, P less than 0.001). Ouabain (5 X 10(-4) M) reversed JnetCa to an absorptive flux (serosal minus mucosal flux = -195.8 +/- 41.3 pmol.mg-1.h-1; n = 20, P less than 0.001). Amiloride (1 X 10(-5) M) reduced both fluxes such that JnetCa was not significantly different from zero. Removal of mucosal sodium caused net calcium absorption; removal of serosal sodium caused calcium secretion. When bladders were short circuited, JnetCa decreased to approximately one-third of control value but remained secretory (138.4 +/- 54.3 pmol.mg-1.h-1; n = 9, P less than 0.025). When ouabain was added under short-circuit conditions, JnetCa was similar in magnitude and direction to ouabain under open-circuited conditions (i.e., absorptive). Tissue 45Ca content was approximately equal to 30-fold lower when the isotope was placed in the mucosal bath, suggesting that the apical membrane is the resistance barrier to calcium transport. The results obtained in this study are best explained by postulating a Ca2+-ATPase on the serosa of the turtle bladder epithelium and a sodium-calcium antiporter on the mucosa. In this model, the energy for calcium movement would be supplied, in large part, by the Na+-K+-ATPase. By increasing cell sodium, ouabain would decrease the activity of the mucosal sodium-calcium exchanger (or reverse it), uncovering active calcium transport across the serosa.

[Substances inhibiting amine oxidases. III. Synthesis and amine oxidase inhibition of imidazoquinoline derivatives]

The activity of copper and FAD dependent amine oxidases was tested with some derivatives of 3H-imidazo[4,5-h]quinoline and its isomers 3H-imidazo[4,5-f]quinoline, the chemistry of which is described in the literature (1), and Ki calculated. The methyl derivative of 3H-imidazo[4,5-f]quinoline was found to activate the copper bovine serum enzyme, but inhibits the FAD mitochondrial enzyme.

Effect of parathyroid hormone fragments on calcium transport in toad bladder

Parathyroid hormone (PTH) has a variety of biologic effects which are both dependent and independent on activation of adenylate cyclase. We studied the effects of intact PTH and PTH fragments on water flow and Ca transport in isolated toad bladder sacs. As reported previously by us, PTH (1-84) significantly stimulated basal water flow in isolated toad bladder sacs. Synthetic PTH 1-34, 44-68, 53-84 and 65-84 (1 microgram/ml) had no effect on basal water flow after a 60-min incubation period. Intact PTH (1-84) and synthetic 1-34 PTH significantly inhibited both arginine-vasopressin and cyclic AMP-stimulated water flow. Synthetic PTH 44-68, 53-84 and 65-84 (1 microgram m/ml) had no effect on arginine-vasopressin or cyclic AMP-stimulated water flow after a 60-min incubation. Intact PTH (1-84) and synthetic 1-34 PTH significantly stimulated 45Ca uptake without affecting 45Ca efflux. Synthetic PTH 44-68, 53-84 and 65-84 had no effect on either 45Ca uptake or 45Ca efflux. Although these results suggest that the intact hormone is required for the maximal effect of PTH on water flow, substantial activity resides in the amino terminal fragment of the hormone. No activity per se resides in the carboxy terminal portion of the hormone as regards water flow. Alterations in Ca transport appear to mediate the effect of PTH on water flow. These effects are independent of activation of adenylate cyclase because these hormones also inhibit cyclic AMP-stimulated water flow.

Effect of parathyroid hormone on transport by toad and turtle bladder

We recently demonstrated that parathyroid hormone (PTH) inhibited both vasopressin- and cyclic AMP-stimulated water transport in the toad bladder. This was associated with an increase in calcium uptake by isolated epithelial cells. We postulated that PTH exerts its action on H2O transport by directly stimulating calcium uptake. The current study was designed to compare the effects of PTH and the calcium ionophore, A23187, on H2O and Na transport and H+ secretion in toad and turtle bladders. In toad bladder, PTH and A23187 decreased arginine vasopressin (AVP)-stimulated H2O flow and short-circuit current (SCC) after 60 min serosal incubation. In turtle bladder A23187 decreased SCC to 79.3 +/- 3.6% of base line (P less than 0.05), and significantly decreased RSCC as well. PTH had no effect on SCC or H+ secretion in turtle bladders. Both PTH and A23187 increased 45Ca uptake in toad bladder epithelial cells; only A23187 increased 45Ca uptake in the turtle bladder. The different action of PTH in these two membranes, compared with that of the calcium ionophore, illustrates the selectivity of PTH on membrane transport. PTH increases calcium uptake and decreases transport only in a hormone-sensitive epithelium, whereas the ionophore works in virtually all living membranes. The mode of action of these two agents to increase calcium uptake is, therefore, likely different.

The use of drugs in renal failure

We have tried to emphasize specific variables that impact upon the use of drugs in the patient with renal disease. These variables are complex, often interrelated, and if neglected by the physician will surely lead to unwarranted drug reactions and serious harm to the patient. We have purposely limited the tables of "Selected Pharmacologic Agents" to a few prototypic drugs from each class, emphasizing the newer agents recently introduced in clinical medicine. We strongly recommend that as new drugs are used, the original literature be consulted for verification.

Parathyroid hormone inhibits water flow in the isolated toad bladder

These experiments studied the effect of parathyroid hormone (PTH) (1-84) on water and Ca transport in isolated toad bladder sacs and toad bladder epithelial cells. Serosal addition of PTH significantly inhibited maximal water flow induced by vasopressin or exogenous cyclic AMP. This effect was seen over a wide range of concentrations, with the threshold for the effect occurring at 1 ng/ml. Pretreatment of the toad bladder sacs with prostaglandin inhibitors (indomethacin or ibuprofen, 1 X 10(-6) M) or preincubation in low-Ca medium (0.089 mM) abolished the effect of PTH on vasopressin-stimulated water flow. Pretreatment of the toad bladders with lanthanum (5 X 10(-5) M) also abolished the effect of PTH on vasopressin-stimulated water flow. Synthetic PTH (1-34) inhibited vasopressin-stimulated water flow only at a high concentration (1 microgram/ml). PTH increased 45Ca uptake by toad bladder epithelial cells but had no effect on 45Ca efflux. These results demonstrate that PTH inhibits water transport beyond the generation of cyclic AMP. That the effect of PTH was abolished in a low-Ca medium or by pretreatment with lanthanum suggests that cell Ca uptake is required for the effect of PTH on water transport. That prostaglandin inhibitors also block the effect of PTH on vasopressin-stimulated water flow suggests that prostaglandin synthesis is required for the effect. These data suggest that the effect of PTH on water flow is mediated by an increased cellular uptake of Ca that stimulates prostaglandin release. Prostaglandin release, in turn, appears to mediate the inhibitory effect of PTH on vasopressin-stimulated water transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodialysis clearance of metronidazole and its metabolites

Metronidazole is now being used with increasing frequency for various infectious conditions in patients with renal failure. It is commonly administered to septic patients who have developed acute renal failure requiring hemodialysis. The hemodialysis clearances of metronidazole and its metabolites were evaluated in nine renal failure patients on maintenance hemodialysis. The mean +/- standard deviation clearance and the extraction ratio were 106.9 +/- 16.3 ml/min and 0.65 +/- 0.08, respectively, when regenerated cellulose dialysis membrane was used. The clearance and the extraction ratio with the use of cuprophan membrane were 72.1 +/- 17.3 ml/min and 0.44 +/- 0.12, respectively. The clearances and extraction ratios for the metabolites were similar to those of the parent drug. For both metronidazole and the hydroxy metabolite, the clearance and the extraction ratio demonstrated a statistically significant difference between the regenerated cellulose membrane and the cuprophan membrane. In summary, metronidazole and its metabolites were found to be highly dialyzable with different clearances depending on the specific type of membrane used. However, owing to the relatively wide therapeutic index of the drug, dosage supplementation may be necessary only in seriously ill patients to ensure therapeutic effect.

Effect of cyclic AMP on acidification in the isolated turtle bladder

Cyclic AMP (10 mM) has been demonstrated to inhibit hydrogen ion secretion in the isolated turtle bladder. These experiments were designed to study the effect of cyclic AMP on hydrogen ion secretion in the isolated turtle bladder using both the pH stat and the reverse short circuit current techniques. Sodium transport was measured as the short circuit current. Studies were carried out at 0% CO2 and 1% CO2 at pH 7.4. Cyclic AMP (10 mM) was added to either the serosal or mucosal solutions, and hydrogen ion secretion was measured from 0 to 120 min. In the presence or absence of carbon dioxide, cyclic AMP and dibutyryl cyclic AMP had no effect on hydrogen ion secretion in fasted turtles. The addition of theophylline (10 mM) to the serosal solution, with or without cyclic AMP had no effect on proton secretion. Sodium transport was unchanged from control following serosal or mucosal addition of 10 mM cyclic AMP in the presence or absence of carbon dioxide. In chronically bicarbonate-loaded turtles proton secretion was the same as control fasted turtles. In these animals, however, serosal administration of 10 mM cyclic AMP significantly stimulated bicarbonate secretion. Stimulation of bicarbonate secretion occurred in the presence of a 20 mM bicarbonate gradient. When there was no bicarbonate gradient, cyclic AMP was without effect; cyclic AMP had no effect on bicarbonate permeability when measured in the presence of acetazolamide. These results indicate that cyclic AMP has no effect on hydrogen ion secretion or sodium transport in the isolated turtle bladder when studied at two different rates of acidification (0 and 1% CO2). Cyclic AMP appears to stimulate active bicarbonate secretion.

Cellular mechanisms of drug-induced papillary necrosis

2-Bromoethylamine hydrobromide (BEA) causes complete papillary necrosis within 24-hr of i.v. administration. The mechanism of this effect is unknown. To characterize further the effect of BEA in transporting epithelia, the urinary bladders of toads and turtles were exposed to varying concentrations of BEA in vitro. In the toad bladder, both cyclic AMP- and vasopressin-stimulated water flow were significantly inhibited after 3 hr of exposure to BEA at a concentration as low as 2.5 X 10(-4) g/ml; after 1 and 2 hr no effect on water transport was observed. Serosal administration of BEA to both toad and turtle bladders significantly inhibited sodium transport to 54% of control at the end of 3 hr. The effect on sodium transport was seen as early as 10 min. The threshold for the effect on sodium transport occurred at a concentration less than that observed for water transport. By contrast, BEA had no effect on hydrogen ion secretion in the isolated turtle bladder over a wide range of concentrations. In fact, after 1 hr, BEA significantly stimulated hydrogen ion secretion. In homogenates of stripped turtle bladder mucosa, BEA significantly inhibited total Na-K adenosine triphosphatase and ouabain sensitive Na-K adenosine triphosphatase. Thus, in anuran membranes, BEA inhibits water and sodium transport but has no effect on acidification. These results suggest that its action in vivo may be related to alterations in cell volume regulation resulting from inhibition of sodium transport rather than a nonspecific toxic effect on the inner medullary epithelium.

Treatment of acute cyanide intoxication with hemodialysis

A dramatic response was noted in a patient at our hospital who received hemodialysis therapy for severe acidosis secondary to an unknown toxin, subsequently identified as cyanide. We were unable to find any information concerning the hemodialysis clearance and extraction ratio of cyanide; thus, we studied the effect of hemodialysis in dogs receiving a constant infusion of cyanide with and without a simultaneous infusion of thiosulfate. The hemodialysis clearance of cyanide in the presence of thiosulfate was 38.3 +/- 5.4 ml/min with an extraction ratio of 0.43 +/- 0.06 (n = 4). Hemodialysis was found to increase the lethal dose of cyanide without thiosulfate infusion, and a further increase was noted with the thiosulfate infusion. Thiosulfate promotes mitochondrial metabolism of cyanide to thiocyanate. The end product, thiocyanate, is quickly removed by hemodialysis. We believe that the demonstrated effectiveness of hemodialysis in the treatment of acute cyanide intoxication is related not only to the hemodialysis clearance of cyanide, but also to the removal of its metabolic end product, thiocyanate. Based on our observations, we feel that hemodialysis is an effective adjunct in the treatment of acute cyanide intoxication.

Pathophysiology of drug-induced papillary necrosis

Papillary necrosis, a common cause of renal failure, is a life-threatening pathophysiologic event which may have a multiplicity of mechanisms. The primary functional lesions are salt wastage, impairment of urinary concentrating ability, polyuria, and imbalances of potassium, calcium and phosphate homeostasis; urinary acidification is completely normal. Papillary necrosis is associated with a profound decrease in juxtamedullary nephron glomerular filtration rate, in addition to damage to the papillary collecting duct. 2-Bromoethylamine hydrobromide (BEA) has proved to be a useful tool in elucidating the generation of this important clinical syndrome.

Oxygraphic assay of 3,4-dihydroxyphenylalanine decarboxylase activity by coupled reaction with free and immobilized serum amine oxidase

An oxygraphic method for the assay of 3,4-dihydroxyphenylalanine (Dopa) decarboxylase activity which makes use of the coupled reactions of Dopa decarboxylase with serum amine oxidase is presented. Both free and immobilized amine oxidases were utilized. The assay is simple, rapid, and allows a continuous monitoring of the reaction. The kinetic parameters for Dopa decarboxylase obtained with the coupled assay do not significantly differ from those obtained by standard methods.