Absence of gastrointestinal absorption or urinary excretion of aluminium from an allantoinate complex contained in two antacid formulations in patients with normal renal function

We studied the plasma and urinary excretion levels of aluminum (Al) on day 0, 10 and 30 in 79 patients with gastrointestinal symptoms and normal renal function who were receiving a complex based on Al allantoinates [C4H5N4 O3 Al (OH)2] and [C4H5N4 O3 Cl Al2 (OH)4]. We evaluated the extent of Al absorption after repeated administration of this complex in two antacid formulations, Ulfon Lyoc in lyophilised tablet form (group 1; n = 40) and Ulfon suspension (group 2; n = 39). The total Al load for each antacid and patient was 512 mg daily for a total of 15360 mg during the 30-day treatment. No significant rise in plasma Al concentration was noted with either formulation between day 0 and 10, day 0 and 30 or day 10 and 30, nor was there any significant increase in urinary excretion levels. Al absorption was not increased and no toxic effects were noted, indicating that such formulations are suitable for long-term therapy in patients with gastrointestinal symptoms.

Interaction of metaiodobenzylguanidine with cardioactive drugs: an in vitro study

Metaiodobenzylguanidine (MIBG), an analogue of noradrenaline, is used to explore the functional integrity of sympathetic nerve endings in the human heart. Various drugs inhibit noradrenaline transport systems and may block the uptake of MIBG. As in vivo studies of the effect of these drugs on myocardial [123I]MIBG uptake are often difficult to perform, we used an in vitro human blood platelet model for this purpose. A platelet preparation from healthy volunteers was incubated with [125I]MIBG alone or different concentrations of drugs currently used in cardiology. Labetalol and propranolol inhibited [125I]MIBG uptake, whereas all other drugs tested (other beta-blockers, calcium inhibitors, digoxin and amiodarone) had no effect even at doses exceeding 50 microM. The labetalol dose inhibiting 50% of [125I]MIBG uptake was lower than the plasma concentration of this drug in treated patients, whereas the propranolol dose was higher. This in vitro study of the effect of drugs on MIBG uptake by human blood platelets is predictive of their in vivo effect on myocardial uptake of [123I]MIBG in treated patients, provided that plasma concentration is taken into account.

Gentamicin-induced kidney damage and lipid peroxidation in rats

Although it has been reported that injections of gentamicin induces lipid peroxidation in rat renal cortex (Ramsammy et al. (1985) Biochem. Pharmacol. 34, 3895-3900), our results showed no modification of thiobarbituric-reagent substances (TBARS) or in analysis of the polyunsaturated fatty acid profile. Moreover, endogenous vitamin E and glutathione were not consumed. In in vitro systems, gentamicin incubated with microsomes, homogenates and kidney slices from the normal rat failed to induce lipid peroxidation. We show that the increase in TBARS in vivo detected by Ramsammy et al. was wrongly attributed to the oxidant power of gentamicin. As this antibiotic does react positively to thiobarbituric acid in the presence of a system generating free radicals, it is possible that these authors accidentally introduced such a system into their experiments.

Rapid and specific high-performance liquid chromatographic method for the determination of iodide in urine

A rapid and specific method for the determination of iodide in urine by high-performance liquid chromatography on an anion-exchange column with electrochemical detection is described. The assay is reproducible as judged by the coefficient of variation of less than 4% at all concentrations used. The limit of detection was 0.1 mumol, and the calibration graph was linear for concentrations between 0.1 and 200 mumol. Using this method, healthy volunteers were found to excrete 69 +/- 39 mumol of iodide per mole of creatinine.

Lack of correlation between TBARS production and PUFA degradation during incubation of membrane erythrocytes in an OH. (Fe2+/H2O2) generator system

We investigated the effects of an OH. (Fe2+/H2O2) generator system on erythrocyte membrane, particularly the time-course of lipid peroxidation as estimated by measurement of conjugated dienes, thiobarbituric reactive substances (TBARS), lipofuscin-like pigments, and alpha-tocopherol. Polyunsaturated fatty acids (PUFAs), especially arachidonic acid (20:4 omega 6) and docosahexenoic acid (22:6 omega 3), were also measured. Erythrocyte membranes were suspended in phosphate buffer containing Fe2+ (200 microM) and H2O2 (1.42 mM), and incubated in a shaking water bath at 37 degrees C. Initially, there was an increase in TBARS and lipofuscin-like pigments, two well-known end products of PUFA oxidative degradation, whereas PUFAs remained unchanged (incubation time: 1 h). After two or more hours of incubation, marked lipid peroxidation was noted, with the appearance of conjugated dienes and a decrease of PUFAs, indicating that lipid peroxidation had occurred after a lag phase during which TBARS were not produced from PUFAs. This suggests that another OH. target was involved.

Decreased cerebral 5-HT1A receptors during ageing: reversal by Ginkgo biloba extract (EGb 761)

Investigation of [3H]8-hydroxy-2(di-n-propylamino)tetralin binding to 5-HT1A receptors in cerebral cortex membranes of Wistar rats showed that the maximal number of binding sites (Bmax) was reduced significantly (22%) in aged (24-month-old) as compared with young (4-month-old) animals. Chronic treatment with Ginkgo biloba extract did not alter binding in young rats but increased binding density significantly (33%) in aged rats. These results confirm previously described age-related 5-hydroxytryptaminergic alterations. Together with data in the literature, they also suggest a restorative effect in aged rats, associated with decreased receptor density resulting from the protective action of Ginkgo biloba extract treatment on neuronal membrane.

Iron- and lactic acid-induced lipid peroxidation in rat kidney homogenates and slices

Lactic acid 4 mM acted as a lipoperoxidant by increasing production of thiobarbituric acid-reactive substances (TBARS) in rat kidney slices and homogenates. This effect occurred mainly when slices and homogenates were incubated in a pH 5.4 medium conductive to full expression of compound acidity. TBARS increase was only slight when incubation was performed in Krebs buffer, pH 7.4. Moreover, sodium lactate 4 mM increased TBARS production only when homogenates were incubated in the pH 5.4 medium. Deferoxamine (1 mM) inhibited the prooxidant effect of lactic acid 4 mM, and TBARS increase was correlated with iron release. The iron mobilized may come from reserves where it is weakly bound or from ferritin; and ascorbic acid, present in low quantities in kidney, might trigger the release of this product.

Age-related changes of noradrenergic-NPY interaction in rat brain: norepinephrine, NPY levels and alpha-adrenoceptors

Noradrenergic-neuropeptide Y interaction, which is implicated in different physiological functions, was studied in senescent rats. Norepinephrine (NE) and neuropeptide Y (NPY) levels were measured in brainstem and hypothalamus, and alpha-adrenergic binding was investigated in brainstem in young (4 months) and old (34 months) Wistar rats. NE concentration was the same in senescent rats, whereas NPY concentration was decreased both in brainstem and hypothalamus compared to levels in young rats. [3H]prazosin binding to alpha 1-adrenoceptors was not modified, but [3H]rauwolscine binding to alpha 2-adrenoceptors was altered with age. In fact, the density of alpha 2-adrenoceptors (Bmax) was lower, while the binding affinity (Kd) was increased in old compared to young rats. These results suggest that the decrease of NPY levels could be one of the possible reasons for changes in [3H]rauwolscine binding to alpha 2-adrenoceptors in old rats. The G-protein-adenylate cyclase system, which is impaired in senescent rats, could be involved in the disorganization of noradrenergic-NPY interaction.

Endothelin modulates dihydropyridine receptor decreased binding in hippocampal slices from normotensive and spontaneously hypertensive rats

Previous studies in rats have demonstrated both the link between voltage-operated calcium channels and endothelin and their cerebral involvement in the pathophysiology of spontaneous hypertension. In the present study, the interaction of endothelin with specific dihydropyridine (DHP) binding sites was investigated using the brain slices model. In rat hippocampal slices, pre-incubation with Bay K 8644 decreased [3H] (+) PN 200-110 binding. There was no difference in agonist-induced decrease of DHP binding in normotensive and spontaneously hypertensive (SH) rats. The effect of Bay K 8644 was partially inhibited by endothelin but not by angiotensin in both normotensive and hypertensive rats. These data compared to those of other studies suggest that DHP binding sites which are regulated by endothelin are post-synaptic. We conclude that brain slices provide a good in vitro model to study DHP receptor regulation and to explore endothelin interactions with DHP-sensitive Ca2+ channels.

Evidence of lipoperoxidation induced by lactic acid on kidney homogenates

Sawas and Gilbert (Arch. Int. Pharmacodyn. Ther., 276 (1985) 301-312) reported that the commercial solution of haloperidol induces lipoperoxidation of kidney homogenates from Sprague-Dawley rats. However, it would appear that this effect is attributable to the excipient, lactic acid, rather than to haloperidol itself. Lactic acid enhances susceptibility to lipoperoxidation of kidney homogenates in a dose- and time-dependent manner by increasing production of thiobarbituric acid-reactive substances and slightly decreasing polyunsaturated fatty acids such as arachidonic acid and docosahexaenoic acid. This stimulation of lipoperoxidation may be attributed to a mechanism less dependent on enzymatic action than on Fe2+ and Fe3+. Lactic acid may facilitate iron release and formation of iron complexes, factors which increase susceptibility to oxidative stress.

A comparative study of enzymuria, in the rat, of the drug combinations amikacin/vancomycin and amikacin/teicoplanin

The aim of this study was to compare nephrotoxicity of the combinations amikacin/vancomycin and amikacin/teicoplanin. Eighteen male Wistar rats were divided into 3 groups of 6 animals each. The first group received 50 mg.kg-1 of amikacin (i.m. route) and 100 mg.kg-1 of vancomycin (i.p. route). The second group received 50 mg.kg-1 of amikacin (i.m. route) and 40 mg.kg-1 of teicoplanin (i.p. route). The third group received an isotonic solution of sodium chloride. The antibiotics were injected for a period of 6 days. Urine samples of animals were taken 24 h before the beginning of the experiment, then every day, throughout the duration of the treatment (6 days), continuing for an additional 3 days following completion of the administration of the drugs. There were no significant modifications in the urinary excretions of alanine aminopeptidase and the creatinine between the 3 groups; but in the group receiving amikacin/teicoplanin, we observed between days 3 and 8 an increase in the excretion of N-acetyl-beta-D- glucosaminidase when compared to the group receiving amikacin/vancomycin (p < or = 0.05) and to the control group (p < or = 0.01).

Cu(2+)-induced lipid oxidation in plasma: questionable relation between cholesterol oxidation and LDL modification

Oxidatively modified low-density lipoproteins (LDL) may be involved in the process of cholesterol deposition in arteries. Because of their cytotoxicity, oxysterols resulting from cholesterol oxidation could be a contributing factor in this process. Studies in this area have generally been performed on purified LDL, but in our research whole plasma was exposed to the oxidizing action of copper. Oxidation of the ring structure, which is at the origin of oxysterols, apparently occurs once most polyunsaturated fatty acids have disappeared. Hydrated LDL density reaches a value identical to that obtained during oxidation of LDL by endothelial cells, whereas the ring structure remains unmodified.

Chrononephrotoxicity in Rat of a Vancomycin and Gentamicin Combination

The effect of time of administration on excretion of two brush border enzymes--alanine aminopeptidase (AAP) and gamma-glutamyl transferase (gamma GT), and a lysosomal enzyme, N-acetyl-beta-D-glucosaminidase (NAG) with a single high dose of vancomycin, gentamicin or a combination of vancomycin and gentamicin was studied in male Wistar rats and compared with elimination of a control group. The rats received vancomycin intraperitoneally (200 mg.kg-1), gentamicin intramuscularly (100 mg.kg-1) or the combination of the drugs by the same route. A control group received isotonic NaCl solution. The four groups of animals received a single injection at 8 a.m., 2 p.m., 8 p.m., and 2 a.m. and urine excretion values for AAP, gamma GT and NAG were determined 24 hr later. The results show that the nephrotoxicity of gentamicin + vancomycin is greater than that observed with gentamicin, which again is greater than that observed with vancomycin. Furthermore, circadian variations in renal toxicity were observed, the least occurring at 8 a.m.

Rapid high-performance liquid chromatographic assay of chlorophacinone in human serum

A simple procedure for the determination of chlorophacinone in human serum by high-performance liquid chromatography is reported. After addition of a suitable internal standard, unknown samples were extracted at acid pH with ethyl acetate. The reconstituted methanolic extract was directly injected into the liquid chromatograph. Separation was performed with a Lichrospher C18 5-microns column with a methanol-phosphate buffer (85:15, v/v) mobile phase. The eluent was monitored with UV detection at 286 nm. The method was found to be sufficiently rapid, reproducible, selective, and sensitive for use in clinical and experimental pharmacokinetic studies. Application of this method to 20 intoxicated patients indicated that the risk of bleeding syndrome, which is always associated with this kind of intoxication, is no longer present when chlorophacinone levels drop to below 1 microgram/mL.

[Circadian variations in the nephrotoxicity of the vancomycin-gentamicin combination in rats]

Male Wistar rats were used to evaluate the influence of time of administration of a single high dose of vancomycin (V), gentamicin (G) or vancomycin-gentamicin combination (V/G) on excretion of a brush border enzyme, alanine aminopeptidase (AAP) and of a lysosomal enzyme, N-acetyl-beta-D-glucosaminidase (NAG). Increased urinary excretion is considered as an early manifestation of renal toxicity. The rats were placed in temperature-controlled quarters with intermittent lighting (12 hours light/12 hours dark). V was given intraperitoneally in a dose of 200 mg/kg, G was given intramuscularly in a dose of 100 mg/kg, and the V/G combination was given in the same doses and by the same routes as each drug alone. A control batch of rats received an intraperitoneal injection of saline. In the four batches, the injection was given at 8 am, 2 pm, 8 pm and 2 am. Substantial brush border toxicity was found. Toxicity of G was greatest at 2 pm and lowest at 2 am, whereas for V, toxicity was greatest at 2 am and lowest at 2 pm. With the V/G combination, brush border toxicity was greatest at 2 am and lowest at 8 am. Lysosomal toxicity was no significant after administration of V or G. In contrast, the V/G combination induced very significant lysosomal toxicity which was greatest at 2 pm and smallest at 8 am. These results show that circadian variations in renal toxicity occur not only with V and G alone but also with the V/G combination.

Aluminum transfer as glutamate complex through blood-brain barrier. Possible implication in dialysis encephalopathy

In vitro distribution of aluminium between plasma and erythrocytes has been studied in the presence of variable amounts of sodium L-glutamate. With a red blood cell suspension in isotonic sodium chloride, aluminium remains confined in erythrocytes even when the sodium L-glutamate concentration increases in the medium. Aluminium initially present in plasma penetrates red blood cells when sodium L-glutamate increases in whole blood, showing that this metal is able in vitro to cross the erythrocyte membrane as glutamate complex. In vivo experiments with male Wistar rats prove that aluminium is also able to pass the blood--brain barrier as glutamate complex and deposit in the brain cortex.

Seasonal effects on the daily variations of gentamicin-induced nephrotoxicity

The effect on kidney damage of the season of year at which gentamicin was administered to rats was studied. Rats received a single intramuscular dose of 200 mg/kg gentamicin at four different times of the day (08.00, 14.00, 20.00 or 02.00 hours. Studies were carried out in January-February, March-April, June-July and October-November. The nephrotoxicity was assessed by the increase of three urinary enzymes: two brush border enzymes, gamma-glutamyl transferase and alanine aminopeptidase, and a lysosomal enzyme: N-acetyl-beta-D-glucosaminidase. The results show that when the injection is administered at 20.00 hours in the January-February and the October-November studies and at 08.00 hours in the March-April study and at 14.00 hours in the June-July study there is a significant increase in the excretion of these enzymes. The renal toxicity of gentamicin therefore has circadian variations as well as seasonal variations. The peak enzyme level is displaced from the start to the end of the rest period of rats depending upon the time of year.

Polyunsaturated fatty acid profiles and alpha-tocopherol levels in plasma and whole blood incubated with copper. Evidence of inhibition of lipoperoxidation in plasma by hemolysate

Polyunsaturated fatty acid (PUFA) profiles and alpha-tocopherol levels were studied in human plasma and whole blood incubated with copper under air or nitrogen. In plasma, both PUFAs and alpha-tocopherol disappeared. The results were completely different in whole blood: (i) in plasma, while alpha-tocopherol decreased in the same manner as in plasma incubated alone, profiles of PUFA were only slightly modified. So, in spite of the absence of alpha-tocopherol, lipoperoxidation was not very marked. That is why the release of a protective factor from erythrocytes during hemolysis was under consideration. This was confirmed by the complete inhibition of degradation of PUFAs in plasma when hemolysate was added; (ii) In erythrocytes, no modification in PUFA profiles could be detected while alpha-tocopherol decreased slightly. Thus, not only do erythrocytes resist the copper-dependent oxidative stress in an incredible manner, but they also seem to protect plasma at the time of hemolysis.