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PubMed2000

Effect of estrogen on intestinal strontium absorption in postmenopausal women.

OBJECTIVES: there is considerable uncertainty about the underlying cause of decreased intestinal calcium absorption that occurs in postmenopausal women. In a previous study, estrogen treatment did not result in an increased intestinal calcium absorption using strontium as a marker. A possible explanation could be that the calcium/strontium load given to the women was too high ( approximately 600 mg Ca), which might result in an insensitive test with respect to the possible stimulation of active strontium transport by estrogen. Therefore, the purpose of this study was to reinvestigate the effect of estrogen on active intestinal strontium absorption using a load of 2.5 mmol of strontium only. METHODS: the effect of estrogen on intestinal strontium absorption was measured in eight normal postmenopausal women. The study included two baseline strontium absorption tests, which were performed with an interval of 10 days for calculating the within subject variation (SER). Thereafter the effect of 2 months of estrogen treatment on intestinal strontium absorption was assessed. Fractional absorption (FC(240)) and the area under the concentration time curve (AUC) 4 h after an oral strontium load of 2.5 mmol were calculated. RESULTS: the within subject SER of FC(240) and AUC(0-240) were 2.3+/-0.76 and 1.2+/-0.41, respectively. FC(240) and AUC(0-240) of strontium were unchanged after treatment with estrogen. CONCLUSIONS: in normal postmenopausal women, we did not find a modulating effect of short-term treatment with a (supra) physiological dose of estrogen on intestinal calcium absorption as measured by the strontium absorption test.

Area Under Curve↗
PubMed2006

Structural studies of human alkaline phosphatase in complex with strontium: implication for its secondary effect in bones.

Strontium is used in the treatment of osteoporosis as a ranelate compound, and in the treatment of painful scattered bone metastases as isotope. At very high doses and in certain conditions, it can lead to osteomalacia characterized by impairment of bone mineralization. The osteomalacia symptoms resemble those of hypophosphatasia, a rare inherited disorder associated with mutations in the gene encoding for tissue-nonspecific alkaline phosphatase (TNAP). Human alkaline phosphatases have four metal binding sites--two for zinc, one for magnesium, and one for calcium ion--that can be substituted by strontium. Here we present the crystal structure of strontium-substituted human placental alkaline phosphatase (PLAP), a related isozyme of TNAP, in which such replacement can have important physiological implications. The structure shows that strontium substitutes the calcium ion with concomitant modification of the metal coordination. The use of the flexible and polarizable force-field TCPEp (topological and classical polarization effects for proteins) predicts that calcium or strontium has similar interaction energies at the calcium-binding site of PLAP. Since calcium helps stabilize a large area that includes loops 210-228 and 250-297, its substitution by strontium could affect the stability of this region. Energy calculations suggest that only at high doses of strontium, comparable to those found for calcium, can strontium substitute for calcium. Since osteomalacia is observed after ingestion of high doses of strontium, alkaline phosphatase is likely to be one of the targets of strontium, and thus this enzyme might be involved in this disease.

Alkaline Phosphatase↗
PubMed2001

Strontium ranelate inhibits bone resorption while maintaining bone formation in alveolar bone in monkeys (Macaca fascicularis).

Strontium ranelate (S12911) has previously been shown to stimulate bone formation and inhibit bone resorption in rats. To determine whether strontium ranelate affects normal bone remodeling, we studied the effect of strontium ranelate on alveolar bone in monkeys. Strontium ranelate, at dosages of 100, 275, and 750 mg/kg per day, or vehicle, were given by gavage to 31 normal adult monkeys (Macaca fascicularis) (15 males, 16 females), aged 3-4 years. Treatment for 6 months with strontium ranelate resulted in an increase in plasma strontium concentration. Histomorphometric analyses of indices of bone formation and resorption were determined in standardized areas of alveolar bone. Treatment with strontium ranelate decreased the histomorphometric indices of bone resorption (osteoclast surface and number) with a maximal significant effect at the highest dose tested. In contrast to this inhibitory effect on bone resorption, strontium ranelate maintained bone formation. Although the amount of osteoid tended to increase, strontium ranelate, even at the highest dose, had no deleterious effect on bone mineralization, as evaluated by mineral apposition rate and osteoid thickness. These findings show that strontium ranelate decreases indices of bone resorption while maintaining bone formation in the alveolar bone in monkeys.

Alveolar Bone Loss↗
PubMed2006

Comprehensive therapy in osteoporosis using a single drug: from ADFR to strontium ranelate.

In vitro, strontium ranelate increases collagen and non-collagenic proteins synthesis by mature osteoblast enriched cells. The effects of strontium ranelate on bone formation were confirmed as the drug enhanced preosteoblastic cell replication. In the isolated rat osteoclast, a preincubation of bone slices with strontium ranelate induced a dose-dependent inhibition of the bone resorbing activity of treated rat osteoclast. Strontium ranelate dose-dependently inhibited preosteoclast differentiation. In a phase II dose ranging trial Strontium ranelate (500 mg, 1000 mg, 2000 mg/day) or placebo were given to 353 postmenopausal women with prevalent vertebral osteoporosis. At the conclusion of this 2-year study, the annual increase in lumbar BMD of the group receiving 2000 mg of strontium ranelate was + 7.3%, a significant increase in bone alkaline phosphatase, over a 6-month period and a significant decrease in N-telopeptide crosslinks throughout the 2-year period were seen. During the second year of treatment, the dose of 2000 mg was associated with a 44% reduction in the number of patients experiencing a new vertebral deformity. The primary analysis of the SOTI study, evaluating the effect of strontium ranelate 2000 mg on vertebral fracture rates, revealed a 41% reduction in the relative risk of patient experiencing a first new vertebral fracture with strontium ranelate throughout the 3-year study. The TROPOS study showed a significant reduction in the risk of experiencing a first non-vertebral fracture by 16% in the group treated with strontium ranelate throughout the 3-year study. A reduction in the risk of experiencing a hip fracture by 36% was also demonstrated in the patients at high risk of hip fracture (age > or =74 years and Femoral Neck T score < or = -2.4 according to NHANES normative value). All these results suggest that strontium ranelate is a new, effective and safe treatment of vertebral and non-vertebral osteoporosis, with a unique mode of action.

Animals↗
PubMed1999

Removal of strontium by the chelating agent acetylamino propylidene diphosphonic acid in rats.

Studies of the effects of the chelating agent, calcium acetylamino propylidene diphosphonic acid (Ca-APDA), on the removal of radioactive strontium with two administration modalities were carried out in rats. The parenteral (intraperitoneal) administration of 150, 300, or 600 mg kg(-1) Ca-APDA was carried out for 3 d, 10 min after exposure of the animals to the strontium injection. On the first day post-treatment, the retention of strontium in the whole body decreased to 90.1%, 83.9%, and 35.1% that of the control level, respectively. The strontium deposited in femur of 600 mg kg(-1) Ca-APDA group was lowered to 28.4% of the control value. A single oral dose of 600 mg kg(-1) Ca-APDA administered simultaneously with, or 10 min after, oral administration of strontium, radionuclide retention in the whole body was reduced after 1 d to 42.9% and 31.9% of the control, respectively; meanwhile the strontium deposited in the femur was reduced to 16.9% and 29.3% of the control. In conclusion, the results indicate the efficacy of the new agent, Ca-APDA, to remove radioactive strontium from the body, or to inhibit the strontium intestinal absorption, in radio-strontium contaminated individuals.

Administration, Oral↗
PubMed1994

A comparison of the palliative effects of strontium-89 and external beam radiotherapy in metastatic prostate cancer.

From 1988 to 1991, 284 patients with prostatic cancer and painful bone metastases were treated with either radiotherapy or strontium-89 (200 MBq). Patients were first stratified according to suitability for local or hemibody radiotherapy, then randomly allocated that form of treatment or strontium-89 (i.v. injection). After 4, 8 and 12 weeks pain sites were mapped, toxicity monitored, and all additional palliative treatments recorded. There was no significant difference in median survival (after > 80% had died); 33 weeks following strontium-89 and 28 weeks following radiotherapy (p = 0.1). All treatments provided effective pain relief; improvement was sustained to 3 months in 63.6% after hemibody radiotherapy compared with 66.1% after strontium-89, and in 61% after local radiotherapy compared with 65.9% in the comparable strontium-89 group. Fewer patients reported new pain sites after strontium-89 than after local or hemibody radiotherapy (p < 0.05). Radiotherapy to a new site was required by 12 patients in the local radiotherapy group compared with 2 after strontium-89 (p < 0.01), although there was no significant difference between hemibody radiotherapy (6 patients) and strontium-89 (9 patients) in this respect. Platelets and leukocytes fell by an average 30-40% after strontium-89 but sequelae were uncommon, and other symptoms rare.

Aged↗
PubMed1993

Results of a randomized phase-III trial to evaluate the efficacy of strontium-89 adjuvant to local field external beam irradiation in the management of endocrine resistant metastatic prostate cancer.

PURPOSE: A large proportion of the practice of radiotherapy in the management of metastatic adenocarcinoma of the prostate is associated with palliation of pain from osseous metastases and improving quality of life. Radiation therapy is well known to be effective in treating painful sites and may also be effective in reducing the propensity for adjuvantly treated disease to become symptomatic. Strontium-89 is a systemic radionuclide that has clinical efficacy in the palliation of pain from bony metastases. METHODS AND MATERIALS: The study was a Phase-III randomized placebo control trial performed in eight Canadian Cancer Centers to evaluate the effectiveness of strontium-89 as an adjunct to local field radiotherapy. Patients with endocrine refractory metastatic prostate cancer received local field radiotherapy and either strontium-89 as a single injection of 10.8 mCi or placebo. RESULTS: One hundred twenty-six patients were recruited. No significant differences in survival or in relief of pain at the index site where noted. Intake of analgesics over time demonstrated a significant reduction in the arm treated with strontium-89. Progression of pain as measured by sites of new pain or the requirement for radiotherapy showed statistically significant differences between the arms in favor of strontium-89. Tumor makers including prostate specific antigen, acid phosphatase, and alkaline phosphatase were also reduced in patients receiving strontium-89. A Quality-of-Life analysis was performed as a multivariate data set and demonstrated an overall superiority of strontium-89 with alleviation of pain and improvement in physical activity being statistically significant. Toxicity was evaluated and demonstrated increased hematological toxicity in the group receiving strontium-89. CONCLUSIONS: It is concluded that the addition of strontium-89 is an effective adjuvant therapy to local field radiotherapy reducing progression of disease as evidenced by new sites of pain and the requirement of further radiotherapy and improving quality-of-life and need for analgesic support in this group of patients.

Aged↗
PubMed1999

Increased serum strontium levels in dialysis patients: an epidemiological survey.

BACKGROUND: We previously reported on increased bone strontium levels in dialysis patients with osteomalacia versus those presenting other types of renal osteodystrophy. A causal role of strontium in the development of osteomalacia was established in a chronic renal failure rat model. METHODS: To further elucidate the latter issue and to find out whether dialysis patients from particular centers/countries are at an increased risk for strontium accumulation, a worldwide multicenter study was established. In total, 834 patients from 34 dialysis centers in 23 countries were included. In each of the patients, a serum sample was taken for strontium determination, and water and dialysate samples were taken at the various steps of the water purification process. For each patient clinical data and for each center dialysis modalities were recorded. RESULTS: Strontium levels in serum of dialysis patients showed major differences between the various centers, ranging from mean values of 25 +/- 8 microgram/liter in the center with the lowest level up to 466 +/- 90 microgram/liter in the center with the highest concentration. It is of interest that these high levels were mainly found in developing countries. Furthermore, our data point toward a role of the final dialysate in the accumulation of the element, as indicated by the strong correlation (r = 0.74, P < 0.001) between mean serum and dialysate strontium levels. As the high tap water concentration of strontium was adequately reduced during the water purification process, contamination of the final dialysis fluid occurred by the addition of concentrates contaminated with strontium. Besides the dialysate, other factors, such as duration of dialysis, vitamin D supplements, or types of phosphate binders, played a less important role in the accumulation of the element. CONCLUSIONS: Data of this multicenter study indicate patients of particular dialysis centers to be at an increased risk for strontium accumulation, the clinical consequence of which is under current investigation.

Adult↗
PubMedDate not supplied

Strontium isotopic identification of water-rock interaction and ground water mixing.

87Sr/86Sr ratios of ground waters in the Bighorn and Laramie basins' carbonate and carbonate-cemented aquifer systems, Wyoming, United States, reflect the distinctive strontium isotope signatures of the minerals in their respective aquifers. Well water samples from the Madison Aquifer (Bighorn Basin) have strontium isotopic ratios that match their carbonate host rocks. Casper Aquifer ground waters (Laramie Basin) have strontium isotopic ratios that differ from the bulk host rock; however, stepwise leaching of Casper Sandstone indicates that most of the strontium in Casper Aquifer ground waters is acquired from preferential dissolution of carbonate cement. Strontium isotope data from both Bighorn and Laramie basins, along with dye tracing experiments in the Bighorn Basin and tritium data from the Laramie Basin, suggest that waters in carbonate or carbonate-cemented aquifers acquire their strontium isotope composition very quickly--on the order of decades. Strontium isotopes were also used successfully to verify previously identified mixed Redbeds-Casper ground waters in the Laramie Basin. The strontium isotopic compositions of ground waters near Precambrian outcrops also suggest previously unrecognized mixing between Casper and Precambrian aquifers. These results demonstrate the utility of strontium isotopic ratio data in identifying ground water sources and aquifer interactions.

Environmental Monitoring↗
PubMed2006

The employment of strontium to activate mouse oocytes: effects on spermatid-injection outcome.

The present research investigated the effects of various strontium concentrations, in combination with different incubation periods, on mouse parthenogentic oocyte activation and blastocyst development. The results for blastocyst development showed a trend indicating that 10 mM strontium for 3 h was the optimal strontium protocol. Ethanol, an agent that incites oocyte activation via a monotonic rise in calcium, was employed as a control. The outcome of blastocyst formation arising from parthenogenic ethanol activation was significantly less (P < 0.001) than that achieved by the optimal strontium protocol. To assess the impact of strontium oocyte activation on embryo viability following fertilization with immature germ cells, the protocol of 10 mM strontium for 3 h was applied to oocytes injected with round spermatids and then compared with other protocols. The results indicate that following round-spermatid injection the benefits derived from strontium artificial oocyte activation are evident during both pre- and post-implantation development. However, in order to adjust the protocol to the most effective round-spermatid injection in relation to the oocyte cell cycle, injection was done 1.5 h after strontium activation followed by another 1.5 h activation in strontium. The implementation of round-spermatid injection in combination with this oocyte-activation protocol led to live-birth outcomes not significantly different to those outcomes obtained by mature spermatozoa.

Animals↗
PubMed1976

Metabolic balances of strontium in man.

Stable strontium balances were determined in man under strictly controlled dietary conditions in control studies and during both oral and intravenous administration of stable strontium. The diet contained about 1 mg strontium per day and most of this (88%) was excreted in stool while 17.5 per cent was excreted in urine, so that the balance was very slightly negative. During the oral intake of 1536 mg strontium per day, given as the lactate, the urinary and the fecal strontium excretions increased markedly and the balance became strongly positive. During the 6-day periods of intravenous infusions of stable strontium as the gluconate, 30-40 per cent of the infused amount was excreted in the urine and 5-10 per cent in stool. A high percentage of the strontium retained during both oral and intravenous administration was excreted in 30 days after the discontinuation of the strontium administration and there was no evidence of long term retention. The administration of stable strontium, given either orally or intravenously, was associated with an increase of the urinary calcium excretion.

Administration, Oral↗
PubMed2006

Strontium ranelate: an increased bone quality leading to vertebral antifracture efficacy at all stages.

Strontium ranelate is a new antiosteoporotic treatment with a dual mode of action, both increasing bone formation and decreasing bone resorption, which rebalances bone turnover in favor of bone formation and increases bone strength. The antifracture efficacy of strontium ranelate, 2 g per day orally, in the treatment of postmenopausal osteoporosis has been investigated in a large-scale, international, multicenter, phase 3 program in which more than 7000 patients were recruited. This article deals with the vertebral antifracture efficacy of strontium ranelate in postmenopausal women with osteoporosis. A significant early (after 1 year) and sustained (over 3 years) antifracture efficacy of strontium ranelate, compared with placebo, was demonstrated in patients with prevalent vertebral fracture with reductions in risk of new vertebral fracture of 49% after 1 year (P < 0.001) and 41% over 3 years (P < 0.001). In addition, the relative risk of clinical vertebral fracture was significantly reduced by 52% (P = 0.003) after 1 year and by 38% (P < 0.001) over 3 years in the strontium ranelate group compared with placebo. Strontium ranelate was also demonstrated to significantly decrease the relative risk of vertebral fractures by 45% (P < 0.001) in patients without prevalent vertebral fracture over 3 years, vs. placebo. Bone mineral density was linearly increased during 3 years of treatment with strontium ranelate in comparison with placebo. Strontium ranelate was well tolerated throughout the entire duration of the clinical trials. Thus, strontium ranelate, 2 g per day orally, is a new, effective, and safe treatment for postmenopausal patients with osteoporosis, to reduce the vertebral fracture risk in patients with or without a history of vertebral fracture.

Bone Density Conservation Agents↗
PubMed2001

Strontium ranelate increases cartilage matrix formation.

Based on previous studies showing that strontium ranelate (S12911) modulates bone loss in osteoporosis, it could be hypothesized that this drug also is effective on cartilage degradation in osteoarthritis (OA). This was investigated in vitro on normal and OA human chondrocytes treated or not treated with interleukin-1beta (IL-1beta). This model mimics, in vitro, the imbalance between chondroformation and chondroresorption processes observed in vivo in OA cartilage. Chondrocytes were isolated from cartilage by enzymatic digestion and cultured for 24-72 h with 10(-4)-10(-3) M strontium ranelate, 10(-3) M calcium ranelate, or 2 x 10(-3) M SrCl2 with or without IL-1beta or insulin-like growth factor I (IGF-I). Stromelysin activity and stromelysin quantitation were assayed by spectrofluorometry and enzyme amplified sensitivity immunoassay (EASIA), respectively. Proteoglycans (PG) were quantified using a radioimmunoassay. Newly synthesized glycosaminoglycans (GAGs) were quantified by labeled sulfate (Na2(35)SO4) incorporation. This method allowed the PG size after exclusion chromatography to be determined. Strontium ranelate, calcium ranelate, and SrCl2 did not modify stromelysin synthesis even in the presence of IL-1beta. Calcium ranelate induced stromelysin activation whereas strontium compounds were ineffective. Strontium ranelate and SrCl2 both strongly stimulated PG production suggesting an ionic effect of strontium independent of the organic moiety. Moreover, 10(-3) M strontium ranelate increased the stimulatory effect of IGF-I (10(-9) M) on PG synthesis but did not reverse the inhibitory effect of IL-1beta. Strontium ranelate strongly stimulates human cartilage matrix formation in vitro by a direct ionic effect without stimulating the chondroresorption processes. This finding provides a preclinical basis for in vivo testing of strontium ranelate in OA.

Cartilage↗
PubMed2002

Strontium ranelate in osteoporosis.

Strontium ranelate is composed of an organic moiety (ranelic acid) and of two atoms of stable non-radioactive strontium. In vitro, strontium ranelate increases collagen and non-collagenic proteins synthesis by mature osteoblast enriched cells. The effects of strontium ranelate on bone formation were confirmed as strontium ranelate enhanced pre-osteoblastic cells replication. The stimulation by strontium ranelate of the replication of osteoprogenitor cells and collagen as well as non-collagenic protein synthesis in osteoblasts provides substantial evidence to categorise SR ranelate as a bone forming agent. In the mouse calvaria culture system, SR ranelate induces a dose-dependent inhibition of labelled calcium release. The inhibitory effects of SR ranelate on bone resorption were close to those of salmon calcitonin. In the isolated rat osteoclast assay, a pre-incubation of bone slices with SR ranelate induced a dose-dependent inhibition of the bone resorbing activity of a treated rat osteoclast. SR ranelate also dose-dependently inhibited, in a chicken bone marrow culture, the expression of both CA II and the alpha-subunit of the vitronectin receptor. These effects showing that SR ranelate significantly affects bone resorption due to direct and/or matrix-mediated inhibition of osteoclast activity and also inhibits osteoclasts differentiation are compatible with the profile of an anti-resorptive drug. In normal rats, administration of SR ranelate induces an improvement in the mechanical properties of the humerus and/or the lumbar vertebra associated with a commensurate increase in bone dimension, shaft and volume. This was not related to any change in the stiffness, suggesting the absence of a mineralisation defect. After oral administration of SR ranelate in humans, the absolute bio-availability of SR ranelate is 27 % after a dose of 2g is given as sachets. The simultaneous intake of SR ranelate and calcium remarkably reduces the bio-availability of SR. SR ranelate was administered in 160 early postmenopausal women, in a 24-month, double-blind, placebo-controlled, prospective randomized study. Daily oral dose of 125 mg, 500 mg, 1 g of SR ranelate were compared to a placebo. At the conclusion of the study, the percent variation of lumbar adjusted BMD from baseline was significantly different in the group receiving 1 g/day of SR as compared to placebo (+ 1.41 % versus 0.98 % respectively). Increase in total hip and neck BMD averages respectively 3.2 % and 2.5 %. SR ranelate does not induce any significant adverse reaction compared to those observed in women receiving a placebo for the same duration. In a phase II study, the effect of SR ranelate in postmenopausal women with vertebral osteoporotic fractures were assessed during a double-blind, placebo-controlled trial. SR ranelate (500 mg, 1 g, 2 g per day) or placebo were given to 353 Caucasian women with prevalent osteoporosis. At the conclusion of this two-year study, the annual increase in lumbar adjusted BMD of the group receiving 2 g of SR ranelate was + 2.97 %. This result was significantly different as compared to placebo. A significant decrease in pyridinium crosslinks (NTX) and an increase in bone specific alkaline phosphatase were evident after 3 and 6 months of treatment. During the second year of treatment, the dose of 2 g was associated with a 4 % reduction in the number of patient experiencing a new vertebral deformity. Bone histomorphometry showed no mineralisation defects. The same percentage of withdrawal following an adverse effect was observed for patients receiving placebo and for those receiving 2 g of strontium ranelate. Currently, strontium ranelate is further investigated in a large Phase III program that includes two extensive trials for the treatment of severe osteoporosis, one assessing SR ranelate effects on the risk of vertebral fractures (SOTI) and one evaluating the effects of SR ranelate on peripheral (non spinal) fractures (TROPOS). The primary analysis of the SOTI study, evaluating the effect of 2 g of strontium ranelate on vertebral fracture rates are expected to be released during the summer 2002.

Animals↗
PubMed1987

Incorporation of strontium into the calcium carbonate crystals of the endolymphatic sac in the tree frog (Hyla arborea japonica).

Tree frogs were loaded with strontium chloride (SrCl2). The incorporation of strontium metal into the calcium carbonate (CaCO3) crystals located both in the inner ear and in the endolymphatic sac was studied by x-ray microanalysis (XMA) and scanning electron microscopy (SEM). In the inner ear, strontium was not recognized except for traces in a few crystals. When observed by SEM, these crystals had a faceted body and two pointed ends with rather smooth surfaces. However, in the endolymphatic sac, which greatly expands into the spinal canal, strontium was clearly present at every surface of all crystals. Careful examinations by point and line XMA revealed that strontium x-ray counts were highest at the pointed ends and decreased sharply and then gradually toward the equator of the crystals. SEM observations revealed that the crystals in the endolymphatic sac always had rough and irregular surfaces regardless of their shapes and sizes. Calcium was always found in crystals of both organs. Except for calcium and strontium, other elements including sodium and heavier elements were negligible in XMA. These findings suggest that strontium is incorporated into the crystals only in the endolymphatic sac, and the rough-surfaced covering of these crystals reflects newly deposited strontium salt. It seems to indicate that these crystals grow predominantly by accretion.

Animals↗
PubMed1979

Inhibition of active strontium transport from erythrocyte ghosts by internal calcium: evidence for a specificity controlling site.

The inhibition of strontium transport from erythrocyte ghosts by internal calcium was investigated. When active strontium transport was measured in the presence of increasing levels of internal calcium it was found that the inhibition of strontium transport started at an internal calcium level of 0.3 mM and was virtually complete when this concentration reached 1.0 mM. It was also noted that calcium transport was virtually constant between concentrations of 0.3 and 1.0 mM. This experiment indicated that calcium did not inhibit strontium transport by competing for the active site of the transport system. This inhibition was partially reversed by increasing the internal magnesium concentration from 1 to 4 mM. A higher level of magnesium at the time of lysis and during incubation enhanced strontium transport. However, the inhibition remained noncompetitive with respect to calcium. Manganese was also found to support calcium and strontium transport. However, it could not reverse the inhibition of strontium transport by internal calcium at any concentration tested. In fact, manganese restored the inhibition of strontium transport by calcium in ghosts that were prepared and incubated in solutions that had high magnesium levels.

Biological Transport, Active↗
PubMed1999

Relative and combined effects of ethanol and protein deficiency on strontium and barium bone content and fecal and urinary excretion.

Strontium metabolism has attracted considerable interest because of to its interaction with calcium, the bone alterations detected after treatment with strontium, and its potential value as a paleodietary indicator. The effects of ethanol on strontium and barium metabolism-another divalent cation which also accumulates in bone--is largely unknown. Based on this fact, we have determined bone content and fecal and urinary excretion of Ba and Sr in four groups of eight animals each pair-fed for 8 wk with (1) a nutritionally adequate diet, (2) a 36% (as energy) ethanol-containing isocaloric diet, (3) a 2% protein, isocaloric diet, and (4) a 36% ethanol, 2% protein isocaloric diet, following the Lieber-DeCarli model. Five additional rats were fed with the control diet ad libitum. We have found that ethanol tends to decrease and a low protein diet to increase bone strontium content; the decrease in bone strontium in the ethanol-fed rats is accompanied by an increase in the absolute excretion of strontium in urine. Ethanol also decreases bone barium content, but the effect of ethanol on urinary barium excretion is opposite that of strontium, a decrease. Thus, we conclude that ethanol alters both barium and strontium metabolism and bone deposition.

Animals↗
PubMed2004

The biological role of strontium.

This review summarises old and more recent literature on the biological role of the bone-seeking trace metal strontium (Sr). It covers areas of chemistry, nutrition, toxicity, transport across biological membranes, homeostasis, general physiology, calcium-strontium interactions, and particularly the role of strontium in bone. The promoting action of strontium on calcium uptake into bone at moderate strontium supplementation, and the rachitogenic action of strontium at higher dietary strontium levels are emphasised. The literature is summarised of the novel antiosteoporotic drug strontium ranelate, which appears to act by a combination of reduced bone resorption and increased uptake of calcium into bone.

Animals↗