Parenteral aluminum administration in the dog: I. Plasma kinetics, tissue levels, calcium metabolism, and parathyroid hormone

Treatment of ionized hypercalcemia in 12 cats (2006-2008) using PO-administered alendronate

Background

Long‐term treatment of cats with ionized hypercalcemia using alendronate has not been evaluated.

Hypothesis/Objectives

Alendronate is well tolerated in treatment of ionized hypercalcemia in cats.

Animals

A total of 12 cats with ionized hypercalcemia.

Methods

Prospective study of 12 cats with ionized hypercalcemia of idiopathic origin was identified by telephone and email communication with a convenience sample of consulting veterinarians. Cats were treated with alendronate at a dose of 5–20 mg per feline PO q7d. Serum ionized calcium concentration (iCa) was measured before beginning treatment with alendronate, and after 1, 3, and 6 months of treatment. Alendronate dosage was adjusted according to iCa. Evaluation included physical examination, CBC, biochemistry profile, and diagnostic imaging. The owners and referring veterinarians were questioned about any observed adverse effects. The Wilcoxon matched‐pairs signed rank test was used to compare baseline iCa to iCa at different time periods.

Results

Alendronate treatment resulted in a decrease in iCa in all 12 cats. The median percentage change in iCa was −13.2%, −15.9%, and −18.1% (range, −29.6 to +7.6; −30.5 to −1.9; −45.8 to +1.5%) at the 1, 3, and 6 month time points, respectively. Baseline iCa was significantly different from 1 month (P = .0042), 3 months (P = .0005), and 6 months (P = .0015). No adverse effects were reported for any of the cats.

Conclusions and Clinical Importance

Alendronate was well tolerated and decreased iCa in most cats for the 6‐month period of observation.

Calcitriol, calcidiol, parathyroid hormone, and fibroblast growth factor-23 interactions in chronic kidney disease

Objective

To review the inter-relationships between calcium, phosphorus, parathyroid hormone (PTH), parent and activated vitamin D metabolites (vitamin D, 25(OH)-vitamin D, 1,25(OH)₂-vitamin D, 24,25(OH)₂-vitamin D), and fibroblast growth factor-23 (FGF-23) during chronic kidney disease (CKD) in dogs and cats.

Data Sources

Human and veterinary literature.

Human Data Synthesis

Beneficial effects of calcitriol treatment during CKD have traditionally been attributed to regulation of PTH but new perspectives emphasize direct renoprotective actions independent of PTH and calcium. It is now apparent that calcitriol exerts an important effect on renal tubular reclamation of filtered 25(OH)-vitamin D, which may be important in maintaining adequate circulating 25(OH)-vitamin D. This in turn may be vital for important pleiotropic actions in peripheral tissues through autocrine/paracrine mechanisms that impact the health of those local tissues.

Veterinary Data Synthesis

Limited information is available reporting the benefit of calcitriol treatment in dogs and cats with CKD.

Conclusions

A survival benefit has been shown for dogs with CKD treated with calcitriol compared to placebo. The concentrations of circulating 25(OH)-vitamin D have recently been shown to be low in people and dogs with CKD and are related to survival in people with CKD. Combination therapy for people with CKD using both parental and activated vitamin D compounds is common in human nephrology and there is a developing emphasis using combination treatment with activated vitamin D and renin-angiotensin-aldosterone-system (RAAS) inhibitors.

Toxicology of explosives and fireworks in small animals

Intoxication with explosives or fireworks in dogs or cats is not common, but serious toxicosis can result from exposure to different types of explosives depending on the chemical class of explosive involved. This article will discuss the different types of materials/chemicals, clinical signs of toxicosis, and their treatment. Despite the complexities of explosives and plethora of different devices currently in use worldwide, the toxic potential is more easily explained by looking at the relatively short list of chemical classes used to produce these materials. This article combines structurally similar explosives into different groups and focuses on the toxicity of the most commonly available explosives.

Effect of chronic poisoning with aluminum on the renal handling of phosphate in the rat

The effects of aluminum on renal function and phosphate handling were studied using clearance techniques in chronically-intoxicated rats. Rats were given aluminum hydroxide (80 mg/kg b.w., i.p.), three times per week during 6 months. The phosphate tubular transport capacity was evaluated by determining the maximum tubular transport (TmRPi) and the fractional excretion of phosphate (FE% Pi) during the infusion of phosphate solutions with increasing concentrations (0, 9, 18, 33 mM). Parathyroid gland function was studied using indirect methods: calcemia recovery after EDTA administration and the nephrogenic excretion of cAMP as indicative of renal PTH actions, by RIA. The systemic acid base status was determined and food intake and rat growth were controlled in both groups. No changes were observed in the renal function. Pi reabsorption values per ml glomerular filtration rate (TRPi/GFR microg/ml) for different Pi plasmatic concentrations were distributed following a saturation curve compatible with a saturation kinetics. Aluminum increased TmRPi/GFR in treated animals (T) 76+/-4 as compared with control animals (C) 57+/-7 microg/ml, without a statistical modification in the apparent affinity. The FE% Pi and FE% Na were significantly lower in treated animals than in control animals. There were neither systemic variations in the acid-base balance nor in the Ca and Pi concentrations in plasma. The calcemia recovery following a hypocalcemic stimulus and the nephrogenic excretion of cAMP (T: 44+/-4; C: 91+/-7 pmol/min) were diminished. Considering all these facts, it can be postulated that the aluminum renal effect is associated from a decrease in PTH phosphaturic capacity. Nevertheless, other associated factors like minor phosphate intestinal absorption rate may not be disregarded, even though there were no significant intake variations.

Effect of aluminium hydroxide administration on normal mice: tissue distribution and ultrastructural localization of aluminium in liver

In order to assess the risk of parenteral aluminium (Al) exposure, we evaluated the effects of intraperitoneal administration of aluminium hydroxide, a compound widely used in medicine. Mice (strain Pzh:SFIS) received intraperitoneally, every two weeks 1 mg Al or 0.1 mg Al for five days a week. Controls received injections of saline. Al concentrations in liver, bone and brain were evaluated by electrothermal atomic absorption spectrometry after exposure to 2 mg, 4 mg, and 6 mg Al. The concentration was the highest in liver and occurred after exposure to only 2 mg Al (265.1 +/- 27.7 mg/kg, 233.5 +/- 28.0 mg/kg). Generally further accumulation was not dose- and treatment-dependent. The only exception was a significant Al increase in the liver after exposure to 6 mg Al, injected 0.1 mg Al five days/week. Development of resorption granulomas was observed in the liver, Al being revealed by Morin fluorescence in constituent macrophages and giant cells. By electron probe X-ray microanalysis, Al was identified predominantly in lysosomes of macrophages and Kupffer cells. In tibia of mice, a dose-dependent Al accumulation was observed. The highest level of Al concentration after the 6 mg treatment was 23.5 +/- 3.82 mg/kg and 25.06 +/- 2.3 mg/kg. The Al concentration in the brain of mice had not changed significantly during Al treatment.

Nephrotoxicities of aluminium and/or cadmium-metallothionein in rats: creatinine excretion and metabolism of selected essential metals

The effects of exposure to aluminium (Al) and cadmium (Cd) on urinary creatinine and protein excretion, and the concentrations of calcium, magnesium and copper in kidney and urine were studied in 32 male adult Wistar rats. The animals were divided into 8 groups, groups 1-4 given a calcium-deficient diet (0.01%, i.e. 0.01 g calcium/100 g diet weight) and groups 5-8 a calcium-adequate diet (0.9%) for 6 weeks. Single daily intraperitoneal injections of AlCl3 (10.8 mg Al/kg body weight, per day) were done on 6 consecutive days to groups 3, 4, 7 and 8 during the last week of the experiment. One single intraperitoneal injection of cadmium-metallothionein (Cd-MT, 0.4 mg Cd/kg) was administered 12 hr before the final Al dose to groups 2, 4, 6, and 8 and the rats were sacrificed 47 hr after the Cd-MT injection. The rate of creatinine clearance was significantly lower in rats injected intraperitoneally with either Cd-MT or Al, and the concentrations of magnesium and calcium in urine were lower in rats administered both Al and Cd-MT as compared to those in control groups. Histological examination showed that Al was toxic to the kidney tubule cells of rats, however, an adequate supply of calcium in food protected to some extent the renal tubules from Al toxicity as indicated by a higher creatinine clearance, and there was also less tubule damage as shown by histological examination. The copper concentrations in kidney tissue were lower in groups treated with either Al or Cd-MT.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary and biliary excretion of aluminoxamine and ferrioxamine in dogs with various renal function

We assessed the pharmacokinetics of aluminoxamine and ferrioxamine in dogs with sustained intermittent bile duct ligation and either normal renal function or stable chronic renal failure. A first group of male beagle dogs were given aluminoxamine and ferrioxamine, while a second group received desferrioxamine after loading them with iron and aluminum. Only minute amounts of ferrioxamine and aluminoxamine were found in the bile after administration of these compounds. The distribution volume of aluminoxamine and ferrioxamine appeared to be confined to the extracellular space and their renal excretion correlated with renal function. Administration of desferrioxamine to iron and aluminum-loaded dogs resulted in an increased biliary ferrioxamine but negligible aluminoxamine excretion. Renal clearance of the in vivo formed ferrioxamine and aluminoxamine in this group strongly correlated with renal function. Our observations indicate that biliary excretion of intravenously administered ferrioxamine and aluminoxamine is negligible even in renal failure. The data presented in this study provide indirect evidence that desferrioxamine administration to iron- and aluminum-loaded dogs results in the intra-hepatic formation of ferrioxamine which is partly excreted in the bile. Biliary excretion of aluminoxamine after desferrioxamine administration remained negligible.

Effects of aluminum on rat bone cell populations

Aluminum (Al) loading is associated with reduced bone formation and osteomalacia in human and certain animal models. However, uncertainty exists as to the cellular effect(s) of Al as both inhibition and stimulation of osteoblast proliferation have been reported. Furthermore, the extent to which Al affects osteoprogenitor cell populations is unknown. To determine the cellular effects of Al in the rat, an animal model in which Al bone disease has been produced, we compared the in vitro effect of 10-50 microns Al on the proliferation and hydroxyproline collagen formation of marrow osteoprogenitor stromal cell populations and perinatal rat calvarial osteoblasts. In subconfluent cultures, Al suppressed proliferation of both marrow fibroblast-like stromal cells and calvarial osteoblasts. In confluent cultures, however, Al selectively stimulated periosteal fibroblast and osteoblast DNA synthesis and collagen (hydroxyproline) production, both in the presence or absence of 1,25-dihydroxyvitamin D. Osteocalcin was not detected in osteoblast-conditioned media or extracellular matrix. These observations suggest that the bone formation defect associated with Al toxicity in growing rats may be a function of impaired patterns of osteoprogenitor/osteoblast proliferation. Furthermore, the Al-stimulated increase in collagen formation is consistent with the development of osteomalacia in Al-toxic humans and animals. The mechanism by which Al stimulated DNA synthesis and collagen production in more mature cultures awaits further study.

Single-dose toxicokinetics of aluminum in the rat

The toxicokinetics of aluminum (Al) in male Wistar rats was studied after single intragastric (IG) doses of 1000 and 12,000 micrograms Al/kg and intravenous (IV) doses of 10, 100, 1000, and 12,000 micrograms Al/kg. Serial blood samples, daily samples of urine and feces as well as brain, liver, kidney, spleen, quadriceps muscle, and femur samples were collected. Al was measured by atomic absorption spectrometry. Al blood profiles after IV doses were adequately described by a two-compartment open model. Al toxicokinetics was dose dependent and appeared to plateau at 12,000 micrograms/kg. At IV doses between 10 and 1000 micrograms/kg the terminal half-life of elimination from whole blood (t1/2 beta) increased from 29.9 +/- 7.8 to 209.3 +/- 32.6 min, and the total body clearance (CL) decreased from 2.45 +/- 0.64 to 0.28 +/- 0.03 ml min-1 kg-1. Following an IV bolus of 10 and 100 micrograms/kg the administered Al was recovered completely from urine (94.4% +/- 9.9% and 98.5% +/- 3.2%). Twenty-nine days after the IV dose of 1000 micrograms/kg daily renal excretion decreased to baseline values while only 55.1% +/- 8.0% of the dose was excreted. Nineteen days after the single IV dose of 1000 micrograms/kg Al accumulated in liver (28.1 +/- 7.7 versus 1.7 +/- 0.5 micrograms/g of control rats) and spleen (72.5 +/- 21.1 versus < 0.4 microgram/g). After the single 1000 micrograms/kg IG dose no absorption of Al was detectable. The IG dose of 12,000 micrograms/kg resulted in a maximum blood Al level of 47.9 +/- 12.4 micrograms/l after 50 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Parenteral nutrition-related bone disease

Parenteral nutrition (PN)-related bone disease remains a problem in patients of all ages. Understanding of the pathogenesis of PN-related bone disease is complicated by the effect of underlying illnesses, therapeutic interventions, and pre-existing nutrition deficiencies before the initiation of PN therapy. Interrelation of various nutrients, for example, calcium, phosphorus, and vitamin D, in their effects on bone mineralization, demands simultaneous assessment of the role of multiple nutrients and increases the difficulty in defining the role of a single nutrient in the development of bone disease. However, recent reports indicate that there exist a number of factors important in the development of PN-related bone disease and some factors such as increased mineral requirement are unique to growing infants whereas other factors such as aluminum toxicity may be common to both adult and pediatric populations. Nonnutritional factors, including chronic use of potent loop diuretics and altered acid-base status, can affect urine mineral loss, cell metabolism, and bone mineralization, particularly in small, preterm infants. Current evidence indicates that the cause of PN-related bone disease is multifactorial, and the prevention of PN-related bone disease awaits better delineation of the exact sequence of pathogenic events.

Effect of fluoride on aluminum-induced bone disease in rats with renal failure

Aluminum (Al) accumulation in renal failure is an etiological factor in the pathogenesis of low turnover bone disease. Aluminum-induced impairment of mineralization has been related to a reduced extent of active bone-forming surface. The present study investigated the effect of fluoride, a potent stimulator of osteoblast number, on the toxicity of aluminum in rats with renal failure (Nx). Following a large parenteral aluminum load (3.2 mg/kg x day) over a period of nine weeks, bone histomorphometry of vertebral cancellous bone revealed a severe low-turnover osteodystrophy as evidenced by a fall in osteoblastic osteoid surfaces and mineral apposition rates. Concurrent administration of fluoride [20 mg/liter (F20) or 40 mg/liter (F40) supplied with the drinking water] resulted in a significant increase in the number of osteoblasts (Nx+Al+F40 vs. Nx+Al, 33.75 +/- 2.83 vs. 1.81 +/- 0.43 mm-1, P less than 0.001) together with an overall reduced deposition of aluminum in bone (469.3 +/- 24.6 vs. 592.2 +/- 28.3 micrograms/g, P less than 0.01). However, there was an increase in the fraction of osteoid surface exhibiting stainable aluminum at the bone-osteoid interface (70.7 +/- 7.1 vs. 44.3 +/- 6.0%, P less than 0.005). Fluoride-exposed rats accumulated a significantly larger osteoid volume, suggesting an exacerbation of the osteomalacic lesion, and furthermore, dynamic histomorphometric parameters remained depressed. These results indicate that fluoride has a distinct effect on the pattern of aluminum deposition in bone. In addition, fluoride antagonizes the aluminum-induced reduction in osteoblast number but provides no amelioration of the impaired mineralization in aluminum-intoxicated rats. Thus, in this model a decrease in the extent of osteoblast surface does not account for the development of aluminum-related bone disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue distribution and urinary excretion of essential elements in rats orally exposed to aluminum chloride

The purpose of this study was to determine disorders in the metabolism of the essential elements (Ca, Fe, Cu, and Zn) in some tissues of rats, as well as to detect the dynamics of urinary excretion of these metals after oral administration of 20 mgAl/kg every day for 8 wk. The elements were determined in brain, kidneys, blood, and urine of the animals in 1st, 2nd, 3rd, 4th, and 8th wk after the exposure to AlCl3. After the 1st wk of aluminium administration, we observed increase of Ca and a decrease of Fe in blood. In brain Ca, Fe, and Cu concentrations were significantly higher in Al-treated rats than in controls after 8-wk exposure. The concentration changes of the essential metals in the tissue were accompanied by increase of the Ca, Fe, and Zn urinary excretion. We assume that the increase in urinary excretion of Ca and the decrease of Fe in the blood may be sensitive indicators of oral aluminium administration.

Kinetics of aluminum in rats. II: Dose-dependent urinary and biliary excretion

Previous iv studies from our laboratories have shown that the disappearance half-life of blood aluminum increased with dose. Experiments were initiated to determine if saturation of biliary and/or urinary excretion could be responsible for this dose-dependent behavior. Biliary aluminum excretion (0-12 h) accounted for less than 1% of the injected amount at 0.1- and 1.0-mg/kg doses. During the same interval, urinary excretion accounted for 16.7 +/- 2.66 and 8.85 +/- 2.2% of administered dose at the low and high doses, respectively (p less than 0.05); corresponding long term (0 to 13 or 22 days) urinary recoveries were 37.6 +/- 3.67 and 28.4 +/- 1.88% of the injected dose (p less than 0.05), with most (66-70%) of the excretion occurring in the first 24 h. This is consistent with many previous reports showing that urinary excretion is one major elimination pathway for aluminum. Both biliary and urinary clearances decreased with increasing blood aluminum concentration; the biliary and urinary clearance values at low concentrations (500-900 ng/mL) were approximately four- and threefold higher than the corresponding values at higher concentrations (10,000-12,000 ng/mL), respectively. It appears that this apparent saturability of biliary clearance may be due to concentration-dependent of transfer from blood to liver, rather than from liver to bile. In vitro ultrafiltration studies support the hypothesis that decreases in urinary clearance were due to decreased filterability of aluminum at the glomerulus as its blood concentration was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminium intoxication in a dog

A two-year-old male Barsoi dog was presented after a two-week period of muscle twitching and convulsions during exercise, which worsened to a state of tetraparesis and coma. Removal of a gastric foreign body, containing aluminium, resolved the presenting signs. Parallel with this clinical recovery the elevated serum levels of aluminium decreased to values of two normal control dogs, suggesting that the neurological signs were due to A1 intoxication.

Gallium-67 as a potential marker for aluminium transport in rat brain: implications for Alzheimer's disease

Evidence of a link between aluminium and Alzheimer's disease, parkinsonism-dementia of Guam, and dialysis encephalopathy raises questions regarding the role of this element in the pathogenesis of these conditions. Therefore, we have investigated the use of gallium-67 (67Ga) as a marker for brain uptake of aluminium. The binding of 67Ga to plasma proteins has been studied, and the blood-brain barrier permeability and autoradiographic distribution of this isotope in rat brain determined in vivo. The autoradiographic distribution of 125I-Fe-transferrin receptors in rat brain has also been determined in vitro. Results show that 67Ga was bound to plasma transferrin, entered the brain with a blood-brain barrier permeability of 2.48 x 10(-6) ml/min/g, and showed a marked regional distribution that was very similar to that of 125I-Fe-transferrin receptors. Our data suggest that the vulnerability of the hippocampus, amygdala, and cerebral cortex in conditions such as those mentioned above may be partly due to an increased uptake and deposition of aluminium in these regions by the iron transport system.

Ultrastructural localization of aluminium in liver of aluminium maltol-treated rabbits by laser microprobe mass analysis

By means of laser microprobe mass analysis (LAMMA), we have studied the ultrastructural localization of aluminium in livers of aluminium maltol-treated rabbits. This animal model was developed to study long-term aluminium toxicity using systemic (intravenous) administration of aluminium. We could only detect aluminium in electron-dense inclusion bodies found in large, sometimes multinucleated cells. These results prove that the actual observation of aluminium deposits in liver with LAMMA gives more information than bulk analysis and can be very useful to explore mechanisms of toxicity.

Elevated aluminum persists in serum and tissues of rabbits after a six-hour infusion

The half-life of aluminum was estimated in selected tissues and fluids in a representative mammal, the rabbit. After a single iv aluminum infusion, half-lives were determined by serial killing of rabbits and aluminum quantitation in selected tissues and fluids by electrothermal atomic absorption spectroscopy. Tissues and fluids demonstrating a significant increase 4 hr after the 200 mumol/kg aluminum dose were the bile, kidney, liver, lung, serum, and spleen. Aluminum concentration did not significantly increase above control in the adrenal gland, bone, heart, muscle, testis, thyroid gland, or selected central nervous system regions. Biliary aluminum concentration returned to control within 12 hr after infusion. Estimated half-lives were 113 days in spleen, 74 days in liver, 44 days in lung, 42 days in serum, 4.2 days in kidney cortex, and 2.3 days in kidney medulla. The kidney also demonstrated another half-life greatly exceeding 100 days. The results demonstrate that aluminum persists in various tissues and fluids for different lengths of time. The calculated half-life of aluminum in these tissues is substantially longer than previously estimated half-lives based on serum aluminum determination. The persistence of aluminum in the liver and other tissues may serve as a source of continuous aluminum exposure for sensitive target organs such as the brain. These calculated half-lives establish the normal rate of aluminum elimination from tissues. Future studies could determine the influence of factors such as uremia or chelation therapy on the rate of aluminum elimination from storage sites as well as serum.

The influence of early parathyroidectomy on aluminum-induced rickets in growing uremic rats

Rats were subjected to a two-stage 5/6 nephrectomy and treated with aluminum for 2 and 4 weeks with a cumulative dose of 4.2 and 8.4 mg of aluminum, respectively. Other animals were parathyroidectomized and loaded with 8.4 mg of aluminum for 4 weeks. Histomorphometry and electron microscopy (tibiae), aluminum tissue (bone, kidney, liver) determination, serum (Ca, Mg, Zn, P, urea, creatinine, alkaline phosphatase, 1,25(OH)2D3, PTH) and urine (creatinine, A1) revealed that: (a) a dose of 8.4 mg aluminum was sufficient to induce rickets within 4 weeks of treatment and was associated with decreased serum calcitriol values and high aluminum accumulation within organs (electron-dense material was found in osteoblasts only); (b) previous parathyroidectomy prevented the occurrence of any aluminum-induced alteration of bone. It was associated with higher calcitriol and phosphorus values than in corresponding non-parathyroidectomized rats and significantly reduced aluminum accumulation within organs. The results was influenced neither by a drop in serum calcium values nor by different degrees of renal failure. We suggest that aluminum-induced rickets in growing uremic rats is prevented or delayed when previous parathyroidectomy has been performed.

Kinetics of aluminum in rats I: Dose-dependent elimination from blood after intravenous administration

Aluminum (Al) kinetics after intravenous bolus administration were studied in the rat. The animals received either 0.1 or 1.0 mg/kg (n = 6 at each dose) of elemental Al as the sulfate salt. The Al content of serial blood samples was determined by flameless atomic absorption spectrophotometry. Blood and plasma Al-time profiles after both doses were monoexponential in most cases. Increasing the administered dose increased the elimination half-life (mean +/- SD) from 1.20 +/- 0.25 to 2.41 +/- 0.26 h. A corresponding decrease in systemic clearance was observed (49.6 +/- 11.0 to 18.4 +/- 4.6 mL/kg.h). Both changes were significant (p less than 0.05). Significant differences were also observed in the volume of distribution, the values of which were 78.3 +/- 17.2 and 58.9 +/- 8.5 mL/kg at the low and high doses, respectively. At both doses, blood:plasma ratios ranged from 0.8 to 1.0, indicating considerable uptake/binding of the element by blood cells.

Renal clearance of aluminium: studies in the isolated perfused rat kidney

The model of isolated rat kidney was used to study the renal handling of aluminium (Al). The kidney function remained unchanged at perfusate concentrations of Al in a range of 0.04-12.4 micrograms/ml during a perfusion period of 60 min. The clearance values of Al decreased with increasing concentrations of Al in the perfusate. The fractional Al clearance was reduced from 70% at the lowest Al concentration in the perfusate to 8.2% at the highest Al concentration. The Al content of the kidneys increased dose-dependently and reached a maximum value of 4 micrograms Al per kidney at a perfusate concentration of 5 micrograms Al/ml. Protein-binding studies with Al confirmed the suggestion that renal elimination of Al is dependent on the degree of Al binding. It is proposed that at low Al load in the plasma, the kidney possesses the capability to eliminate Al in an effective manner.

Recent developments in aluminum toxicology

Aluminum is now recognised as an important toxin causing considerable morbidity and mortality, particularly in patients with chronic renal failure. Diseases that have been associated with aluminium include dialysis dementia, renal osteodystrophy and Alzheimer's disease. Aluminum also has an effect on red blood cells, parathyroid glands and chromosomes. Accumulation of aluminium in the body tends to occur when the gastrointestinal barrier is circumvented. This has been identified as a problem during dialysis or intravenous fluid administration. Renal functional impairment results in decreased aluminum excretion and promotes accumulation of the element in the body. Many sources have been shown to be contaminated with aluminium. These include the water used for dialysis; medicines containing aluminium, such as aluminium-containing phosphate binding gels; total parenteral nutrition solutions; processed human serum albumin; intravenous fluids in infants; and other environmental and industrial sources. The management of aluminium toxicity involves the identification of these contaminated sources and subsequent removal of the element. This includes regular monitoring of water used in dialysis. The use of aluminium-containing phosphate binding gels in patients with compromised renal function should be reviewed and alternatives sought. The development of effective aluminium-free phosphate binders is desirable. Once a patient has aluminium toxicity, desferrioxamine (deferoxamine) has been shown to be an effective agent in its chelation and removal.

The influence of dietary calcium reduction on aluminum absorption and kinetics in the rabbit

There is considerable evidence of an aluminum (Al)-calcium (Ca) interaction, including potentiation of Al accumulation and toxicity by Ca deficiency. To elucidate the influence of dietary Ca on Al absorption, rabbits were maintained on a low-Ca (0.024%) or a Ca-replete (0.83%) diet for 2 wk prior to testing. Once weekly, Al hydroxide, nitrate, citrate, or lactate or sucralfate was given orally, or Al lactate was given intravenously (iv). Oral Al bioavailability was determined by comparison of the area under the Al concentration-time curve to that obtained after iv Al. Neither oral Al bioavailability nor the pharmacokinetic parameters of iv Al lactate was significantly affected by dietary Ca concentration. When measured before the weekly Al treatments, total serum Ca of rabbits fed the low-Ca diet averaged 88% of rabbits fed the Ca-replete diet. Total serum Ca 1-72 h after Al treatment decreased from 1% (Al hydroxide) to 15% (Al citrate) below pretreatment concentrations.

Mutagenicity, carcinogenicity and teratogenicity of aluminium

Aluminium and its salts, which are extensively used in the household and in industry, do not constitute a carcinogenic, mutagenic or teratogenic hazard, except, perhaps, in cases of extremely high exposure. The large majority of the experiments performed to assess the carcinogenicity of aluminium in laboratory animals gave negative results or even suggested some antitumor activity. Moreover, epidemiological studies have not provided clear evidence of a carcinogenic hazard of aluminium to man, and short-term tests made in vitro and in vivo to demonstrate mutagenic activity of A1 were negative except for some experiments in plants. The embryotoxic properties suggested by the studies on birds and mammals could result from the influence of A1 on phosphate and calcium metabolism or from interference with the polymerization of microtubules.

Influence of renal impairment, chemical form, and serum protein binding on intravenous and oral aluminum kinetics in the rabbit

The influence of renal impairment on the intravenous kinetics of aluminum (Al) lactate and the oral absorption of eight representative Al forms was determined. The serum protein binding of Al was assessed. Creatinine clearance in renally impaired rabbits was 23% of controls. Systemic clearance of Al was less in renally impaired rabbits (39 vs. 53 ml/hr/kg), as were the steady-state volume of distribution (516 vs. 1175 ml/kg), the half-life of elimination (14 vs. 27 hr), and the mean residence time of Al (14 vs. 25 hr). The shorter Al half-life and mean residence time in renally impaired rabbits were due to a diminished volume of Al distribution. Oral bioavailability of Al in renally intact rabbits ranged from 0.3 to 2.2% (Al borate less than glycinate less than hydroxide less than chloride less than sucralfate less than lactate less than nitrate less than citrate). Renal impairment had little influence on oral bioavailability of most Al forms, although it increased Al citrate absorption to 4.6%. In vitro and in vivo determination of Al ultrafilterability (less than 30,000 D) as an estimate of serum protein binding suggested a greater percentage of ultrafilterable Al species in renally impaired rabbit serum than in control rabbit serum. The increase in ultrafilterable Al species produced the less than expected reduction in Al clearance in renally impaired rabbits. The ultrafilterability of various Al concentrations was greater for citrate greater than lactate greater than nitrate greater than chloride, perhaps partially explaining the similar rank order of oral absorption of these Al forms. The physicochemistry of the eight Al forms was further characterized by determination of their octanol/water partitioning coefficients and their water solubility. There was a significant correlation between the percentage absorbed and the log of the octanol/water partition coefficient. Knowledge of the physicochemistry of Al aids in the understanding of Al pharmacokinetics.

Aluminum intoxication in vitamin D-deficient rats: studies of bone aluminum localization and histomorphometry before and after vitamin D repletion

Aluminum accumulation by both dialysis patients and nonuremic patients, requiring chronic total parenteral nutrition, may be an etiological factor in the development of severe osteomalacia. To study the role of aluminum toxicity in bone, further experiments have been conducted in the nonuremic, vitamin D-deficient rat. Weanling rats were raised on vitamin D-deficient diets, and half received parenteral aluminum (5 mg/wk), for 30 days. In the first experiment low doses of 25-OH cholecalciferol (500 ng/week) were given subcutaneously for a further 30 days. Control rats were maintained on a similar protocol, but were supplemented with cholecalciferol (5 micrograms/week) from the outset until sacrifice at 60 days. In the second experiment a single bolus of cholecalciferol (5 micrograms) was given to study short-term changes in serum biochemistry and bone histology at 96 hr. Quantitative bone histomorphometric analyses of the proximal tibial metaphysis were made in all experimental groups. In the experimental vitamin D-deficient group, with the highest bone aluminum content (as assessed by extraction of whole bone aluminum), X-ray microanalysis was performed to determine the distribution of aluminum in bone tissue and bone cell organelles. The results showed that control rats treated with prolonged aluminum therapy (30 mg over 60 days) had evidence of both reduced osteoid matrix synthesis and mineralization. However, in vitamin D-deficient rats, there was no evidence that aluminum exacerbated the osteomalacic lesion, even though there was histochemical evidence of aluminum deposition at the bone-osteoid interface.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum and bone disorders: with specific reference to aluminum contamination of infant nutrients

Aluminum (Al) impairment of bone matrix formation and mineralization may be mediated by its direct effect on bone cells or indirectly by its effect on parathyroid hormone and calcium metabolism. Its toxic effects are proportional to tissue Al load. Al contamination of nutrients depends on the amount of Al present naturally in chemicals or from the manufacturing process. Intravenous calcium, phosphorus, and albumin solutions have high Al (greater than 500 micrograms/L), whereas crystalline amino acid, sterile water, and dextrose water have low Al (less than 50 micrograms/L) content. Enteral nutrients including human and whole cow milk have low Al, whereas highly processed infant formulas with multiple additives, such as soy formula, preterm infant formula, and formulas for specific disorders are heavily contaminated with Al. Healthy adults are in zero balance for Al. The gastrointestinal tract excludes greater than 95% of dietary Al, and kidney is the dominant organ for Al excretion. However, even with normal renal function, only 30-60% of an Al load from parenteral nutrition is excreted in the urine, resulting in tissue accumulation of Al. The risk for Al toxicity is greatest in infants with chronic renal insufficiency, recipients of long term parenteral nutrition, i.e., no gut barrier to Al loading, and preterm infants with low Al binding capacity. The rapid growth of the infant would theoretically potentiate Al toxicity in all infants, although the critical level of Al loading causing bone disorders is not known. To minimize tissue burden, Al content of infant nutrients should be similar to "background" levels, i.e., similar to whole milk (less than 50 micrograms/L).

Effects of 1 alpha,25- and 24R,25-dihydroxyvitamin D3 on aluminum-induced rickets in growing uremic rats

Rats were subjected to a two-stage subtotal nephrectomy or sham operation, and treated with aluminum (Al) or both aluminum and vitamin D3 metabolites for 5 weeks with a cumulative dose of 13.6 mg aluminum. Animals were injected with 3H-thymidine and 3H-proline. The following analyses were performed: quantitative histology of tibial metaphyses and cytomorphometric electron microscopy of osteoclasts, quantitative (ICP-spectroscopy) and qualitative determination (histochemical staining) of aluminum within organs, and serum biochemistry (Ca, P, Mg, vitamin D3 metabolites, alkaline phosphatase, urea). The following new facts of the aluminum-related bone disease became evident: (a) Application of aluminum to growing uremic rats induced rickets, whose major epiphyseal growth plate changes were 1 alpha,25(OH)2D3-dependent. Addition of 1 alpha,25(OH)2D3 prevented the formation of rachitic metaphysis, but failed to prevent osteoid accumulation on epiphyseal and metaphyseal trabecular surfaces. Moreover, calcitriol produced hyperosteoidosis and osteosclerosis in the same rats. Aluminum did not alter the function of osteoblasts, while osteoclasts seemed inactivated. (b) The development of rickets was associated with suppressed serum levels of 1,25(OH)2D3, reduced phosphorus level and the high content of aluminum in the bone, kidney, and liver. The addition of 24R,25(OH)2D3 markedly exaggerated the reduction of serum levels of calcitriol. We suggested that aluminum induces rickets in growing uremic rats, which consists of two components: vitamin D refractory osteomalacia and 1 alpha,25(OH)2D3-dependent epiphyseal growth plate changes.

Enhanced gastrointestinal absorption of aluminum in uremic rats

To investigate the possibility of enhanced gastrointestinal absorption of aluminum in uremia, we measured the urinary aluminum excretion of rats following an oral load of 11 mg aluminum. Rats, in which uremia had been established by the remnant kidney model, excreted 1.5 to 2.2-fold higher amounts of aluminum in their urine over a collection period of five days compared with their controls. Within this period of time up to 0.17 +/- 0.08% of the oral dose of aluminum was recovered in the urine of the uremic animals. Serum concentrations of aluminum were significantly elevated five hours after ingestion of aluminum, but this increase was similar in rats with normal or reduced renal function. Uremic rats excreted significantly less aluminum during the first 24 hours after i.v. administration of 15 micrograms aluminum if the data were corrected for the higher baseline excretion rates. The excretion rate showed a negative correlation with the serum creatinine. Selective parathyroidectomy had no effect on the pattern or amount of urinary aluminum excretion after an oral load in either uremic rats or in rats with normal renal function. We conclude that the gastrointestinal absorption of aluminum is increased in uremic rats, and that parathyroid hormone has no detectable effect on the magnitude of aluminum absorption, regardless of the renal function in this model.

Aluminium induced damage of the lysosomes in the liver, spleen and kidneys of rats

The influence of repeated aluminium (Al) administration (0.05 or 0.5 mg 100 g-1 b.w.t. i.p. 5 times weekly for 12 weeks) on the lysosomal enzymes N-acetyl-beta-D-glucosaminidase (beta-NAG) and beta-glucuronidase (beta-Gluc) in serum, liver, spleen and kidneys of adult female rats with intact kidneys, (NR), or following partial nephrectomy (5/6 NX) was investigated. After A1 loading, at the high dose only, the beta-NAG in serum and the free beta-NAG in liver, spleen and kidneys increased. Latent beta-NAG levels decreased in all three organs the effect being dose related. Following A1 loading no elevation in total enzyme activity was observed, with one exception. Depending on A1 doses the spleen of the non-operated animals, the liver of both groups of animals and the serum showed a decrease in beta-Gluc activity. No effect on beta-Gluc activity was observed in the spleen of 5/6 NX animals or in the kidneys of either group of animals. The results confirm that high doses of Al induce toxic effects and damage the lysosomes in the liver, the spleen and the kidneys. The results indicate that the extent of lysosomal damage correlates with dose and duration of Al loading. Repeated administration of Al also interferes selectively with enzyme synthesis.

Uptake and distribution of aluminium in rat hepatocytes and its effect on enzyme leakage and lactate formation

Aluminium (Al) chloride (10-200 microM) increased the Al content in hepatocytes isolated from fed male rats in a time- and concentration-dependent manner. After 60 min of incubation with 100 microM Al about 45% of cellular Al was found each in the mitochondrial and the postmitochondrial fraction of hepatocytes, whereas about 5% of Al sedimented with nuclei and cell debris. Concomitantly, the leakage of lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) increased in the presence of Al time- and concentration-dependently, but only to a moderate extent. Aluminium (10-200 microM) also accelerated the formation of lactate by hepatocytes. No significant differences were found in Al uptake and distribution and its effect on LDH leakage and lactate formation when the metal ion was given as AlCl3, Al(NO3)3 or Al(lactate)3. Al concentrations (AlCl3) exceeding 250 microM severely disturbed the determination of LDH, AST and lactate in a cell free system. The data suggest only a moderate toxicity of Al compounds to isolated hepatocytes, when given in amounts approximating (patho)physiological conditions.

Hepatic abnormalities associated with aluminum loading in piglets

Cholestasis is a common complication of total parenteral nutrition (TPN) in infants. A contributing factor to the hepatic dysfunction may be a contaminant of the TPN solution, such as aluminum, that accumulates in liver and may act as a hepatotoxin. To study the hepatic effects of aluminum, growing piglets were given daily intravenous injections of aluminum, 1.5 mg/kg, for 50 days; pair-fed controls were given heparinized saline. At sacrifice, liver and serum were obtained. Liver was analyzed for histopathology and for aluminum content and localization. The hepatocyte lysosomes of the experimental group showed aluminum peaks by x-ray microanalysis, whereas the control group did not. No differences in ultrastructure were noted between the two groups when examined by electron microscopy. Mean serum total bile acid levels (27.8 +/- 15.9 SD vs 6.3 +/- 1.5 mumol/liter, p less than 0.05), mean alkaline phosphatase (309 +/- 108 vs 180 +/- 27 IU/liter, p = NS), and mean hepatic copper content (24.8 +/- 4.5 vs 14.4 +/- micrograms/g dry weight, p less than 0.01), were elevated in the aluminum-loaded piglets, indicating that cholestasis may have been produced. Also, a small but significant reduction in serum levels of 25 hydroxy-vitamin D was found in the aluminum-loaded piglets, suggesting that vitamin D hydroxylation may be impaired. Inasmuch as lysosomal contents are excreted into the bile, aluminum accumulation in lysosomes may alter lysosomal function and possibly affect bile flow or content.

Aluminum action on mouse bone cell metabolism and response to PTH and 1,25(OH)2D3

Aluminum (Al) accumulation in bone is associated with low bone formation and mineralization rates; resorption may also be reduced. The mechanism of these Al-induced changes was investigated using cultured mouse osteoblast-like (OB) and osteoclast-like (OC) cells. The Al effect on bone resorption was measured by the in vitro release of 45Ca and beta-glucuronidase from mouse fetal limb-bones. Al had a biphasic effect. High concentrations (greater than 1.5 X 10(-6) M) of Al inhibited collagen and DNA synthesis, ornithine decarboxylase and alkaline phosphatase activity in OB, and depressed tartrate-resistant acid phosphatase activity in OC. Lower Al concentrations stimulated these cellular activities and 45Ca and beta-glucuronidase release from fetal bones. Al had no effect on basal cAMP levels in OB but inhibited the stimulating effect of bPTH on cAMP content. Al also altered the 1,25(OH)2D3 effects on the ornithine decarboxylase activity of OB cells. These data suggest that: (i) the low bone formation observed in vivo during Al intoxication may be due to the inhibition of collagen synthesis and to depressed cell proliferation; and (ii) Al may indirectly influence bone remodeling by interfering with the actions of bPTH and 1,25(OH)2D3 on bone cells.

The role of aluminum in the development of hypercalcemia in the rat

The present study evaluates the effect of an intravenous (i.v.) aluminum infusion on total and ionized calcium. Seven groups of rats were studied, and it was found that the magnitude of hypercalcemia was dose dependent. During a two hour i.v. infusion containing 0.4 mg aluminum per 100 grams of body weight, the total plasma calcium increased from 9.7 +/- 0.2 to 12.7 +/- 0.7 mg/dl (X +/- SE, P less than 0.02) while the ionized calcium decreased from 5.1 +/- 0.12 to 4.05 +/- 0.24 mg/dl (P less than 0.001). The increase in plasma calcium occurred in intact and parathyroidectomized rats, and the hypercalcemia could not be attributed to changes in PTH, arterial pH, plasma protein, or plasma phosphate. In vitro studies indicate that the addition of aluminum to rat plasma results in decreased ionized calcium concentration. Similarly, ultrafilterable calcium declined from 5.4 +/- 0.17 to 4.53 +/- 0.12 mg/dl (P less than 0.001) after the addition of aluminum to rat plasma. In summary, high levels of intravenous aluminum increase total plasma calcium and decrease ionized calcium. As also supported by in vitro data, the most probable mechanism is increased binding of calcium in the plasma which decreases ionized calcium. As a result of the decreased concentration of ionized calcium, movement of bone and interstitial calcium into the vascular space may occur, thus increasing total plasma calcium.

The effects of aluminum loading on the renal response to parathyroid hormone in the vitamin D-replete rat

Aluminum (Al) may cause vitamin D-resistant osteomalacia and depress the serum levels of immunoreactive parathyroid hormone (iPTH) in patients treated with maintenance dialysis and those on total parental nutrition (TPN). Both conditions have been associated with low serum levels of 1,25(OH)2-vitamin D (1,25(OH)2D). Al may inhibit PTH secretion in vitro; however, induction of hypocalcemia can enhance endogenous PTH secretion in Al-loaded dogs and TPN patients. Despite hypocalcemia and/or increased endogenous iPTH levels, Al-loaded TPN patients fail to show the expected rise in serum 1,25(OH)2D levels. Such observations suggest that Al may impair the renal response to PTH. We studied vitamin D-replete rats given Al or saline vehicle IP for 5 days. Al and control rats then received a saline infusion with an IV bolus of PTH 1-34. Urinary cyclic AMP and P excretion rose in Al and control rats by 1 hr post-PTH, without differences between the groups. Serum P and ionized Ca levels were not different between Al and control rats. In other Al and control rats, serum 1,25(OH)2D levels were measured after saline without PTH. Serum 1,25(OH)2D levels were higher in controls given PTH than in those without, but 1,25(OH)2D levels were not different between Al rats given PTH and those with none. Thus, aluminum does not affect cyclic AMP or P excretion but may impair 25(OH)D-1 alpha-hydroxylase activity in response to PTH.

Tissue distribution of subcutaneously administered aluminum chloride in weanling rabbits

The purpose of our investigation was to determine blood and tissue levels of aluminum (Al) in normal young rabbits. Furthermore, we wished to determine tissue distribution and accumulation of Al as related to its blood concentration in Al-dosed rabbits. The levels of Al accumulated were determined in different tissues of growing rabbits after continuous subcutaneous administration of Al chloride (3.78 mg/d) for 28 d. No signs of toxicity were apparent from comparisons of hematocrit or weight gain between control and Al-dosed rabbits. The largest concentration of the Al was observed in bone, which was also found to have the highest levels in the control rabbit tissues. Following bone, the experimental animals showed the greatest increase of Al levels in kidney cortex, kidney medulla, liver, testes, skeletal muscle, heart, brain white matter, and brain hippocampus, in that order. No significant difference was found in brain grey matter between control and experimental animals. As the brain tissue of the Al-treated animals had the lowest Al level of the tissues measured, it appears that there is a partial blood-brain barrier to entry of Al.

Absorption and disposition of aluminum in the rat

The kinetics of aluminum were determined in the rat. Intravenous bolus and oral doses of 8.1-mg/kg of aluminum as the chloride salt were administered to six rats. Serial blood samples and total urine and feces were collected and assayed for aluminum by atomic absorption spectrophotometry. The fraction absorbed orally (mean +/- SEM) was 0.27 +/- 0.03; the half-life was 5.29 +/- 0.47 h; the steady-state volume of distribution was 38.4 +/- 6.4 mL/kg, and the clearance was 8.87 +/- 1.76 mL X h-1 X kg-1. It was found that aluminum did not significantly penetrate the cellular components of blood. Plasma protein binding was determined to be approximately 98%. Sixty percent of the intravenous dose was excreted in the urine and the remaining 40% was excreted in the feces.

Influence of aluminum on mineralization during matrix-induced bone development

A model of de novo mineralization employing matrix-induced endochondral bone formation in rats was used to study the short-term effects of aluminum on the deposition of calcium and phosphate in vivo. In experiments where systemic aluminum concentrations were elevated, the cellular processes associated with bone development appeared to be normal, if somewhat delayed, however precipitation of the mineral phase was prevented. This suggests a primary direct physical chemical effect of aluminum in vivo on calcification, as suggested by in vitro studies which demonstrate that aluminum is a potent inhibitor of calcium phosphate precipitation. Aluminum salts implanted locally with the matrix appeared to be toxic to the cellular processes leading to chondrogenesis and osteogenesis.

Renal effects of aluminium in uraemic rats and in rats with intact kidney function

The effect on renal function following administration of aluminium (i.p., five times weekly (0.05 or 0.5 mg kg-1 body weight) for 12 weeks) to partially nephrectomized (5/6 NX) or intact female rats was examined. The observed loss of concentrating ability, characterized by increased urine volume and an increased sodium excretion, as well as increased renal excretion of p-aminohippurate (demonstrable after low-dose treatment with nephrotoxins) can be interpreted as an initiation of kidney function injury. No distinct differences in response were observed between partially nephrectomized and intact animals.

Aluminum accumulation in individuals with normal renal function

In individuals with normal renal function, oral aluminum may be absorbed, but the kidneys are able to excrete the load, and significant pathology is not seen. If aluminum is given parenterally, however, it can accumulate in tissues and lead to osteomalacia or aplastic bone lesions. Low calcitriol and PTH levels are often seen, and may contribute to the bone disease. These findings in individuals with normal renal function add to the growing body of evidence that aluminum is toxic to bone.

The case against aluminum affecting parathyroid function

Although there seems to be an interrelationship between aluminum metabolism and toxicity and parathyroid function, this relationship is complex and complicated. At present, the data seem to be too variable to know with certainty what, if any, effect aluminum has on parathyroid function. It is more likely that parathyroid function determines aluminum skeletal toxicity than aluminum determines parathyroid function. This is suggested by the fact that patients with overt hyperparathyroidism are protected from developing aluminum-related bone disease even when they are given large parenteral loads of aluminum. And chronic, parenteral loads of aluminum seem to have little or no effect on the hyperparathyroid state. It remains to be elucidated just how parathyroid hormone might augment total body aluminum burden after oral loading of the element. Also unclear is how parathyroid hormone enhances bone aluminum uptake.