Incorporation and distribution of strontium in bone

The distribution and incorporation of strontium into bone has been examined in rats, monkeys, and humans after oral administration of strontium (either strontium chloride or strontium ranelate). After repeated administration for a sufficient period of time (at least 4 weeks in rats), strontium incorporation into bone reaches a plateau level. This plateau appears to be lower in females than in males due to a difference in the absorption process. Steady-state plasma strontium levels are reached more rapidly than in bones, and within 10 days in the rat. The strontium levels in bone vary according to the anatomical site. However, strontium levels at different skeletal sites are strongly correlated, and the strontium content of the lumbar vertebra may be estimated from iliac crest bone biopsies in monkeys. The strontium levels in bone also vary according to the bone structure and higher amounts of strontium are found in cancellous bone than in cortical bone. Furthermore, at the crystal level, higher concentrations of strontium are observed in newly formed bone than in old bone. After withdrawal of treatment, the bone strontium content rapidly decreases in monkeys. The relatively high clearance rate of strontium from bone can be explained by the mechanisms of its incorporation. Strontium is mainly incorporated by exchange onto the crystal surface. In new bone, only a few strontium atoms may be incorporated into the crystal by ionic substitution of calcium. After treatment withdrawal, strontium exchanged onto the crystal is rapidly eliminated, which leads to a rapid decrease in total bone strontium levels. In summary, incorporation of strontium into bone, mainly by exchange onto the crystal surface, is dependent on the duration of treatment, dose, gender, and skeletal site. Nevertheless, bone strontium content is highly correlated with plasma strontium levels and, in bone, between the different skeletal sites.

Bioactive SrTiO(3) nanotube arrays: strontium delivery platform on Ti-based osteoporotic bone implants

Development of strontium releasing implants capable of stimulating bone formation and inhibiting bone resorption is a desirable solution for curing osteoporosis. In this work, well-ordered SrTiO(3) nanotube arrays capable of Sr release at a slow rate and for a long time are successfully fabricated on titanium by simple hydrothermal treatment of anodized titania nanotubes. This surface architecture combines the functions of nanoscaled topography and Sr release to enhance osseointegration while at the same time leaving space for loading of other functional substances. In vitro experiments reveal that the SrTiO(3) nanotube arrays possess good biocompatibility and can induce precipitation of hydroxyapatite from simulated body fluids (SBF). This Ti-based implant with SrTiO(3) nanotube arrays is an ideal candidate for osteoporotic bone implants. The proposed method can also be extended to load other biologically useful elements such as Mg and Zn.

Strontium 89 therapy for the palliation of pain due to osseous metastases

OBJECTIVE

To present the current state of systemic radiopharmaceutical therapy for the palliation of pain in individuals with metastatic cancer and to evaluate the palliative effect and degree of hemotoxicity of strontium chloride 89 (89Sr) in patients with painful osteoblastic metastases primarily from prostate and breast cancer.

DATA SOURCES AND STUDY SELECTION

A MEDLINE search through December 1994 was performed to identify English-language studies that met the following criteria. All eligible studies reported treatment of patients with painful osteoblastic bony metastases primarily from prostate or breast cancer treated with intravenous 89Sr. For study eligibility, evaluation of clinical response as assessed by the Karnofsky index, need for pain medication, or changes in mobility or sleep patterns was required. Hemotoxicity data were a requirement. A minimum of 10 prostate cancer cases was necessary for study inclusion. Only those studies assessing clinical response following one injection of 89Sr were included. Preliminary reports of cooperative studies were not included. Doses of 89Sr ranged from 0.6 MBq/kg (16 microCi/kg) to 400 MBq (10.8 mCi) per patient. Evaluation of patients for at least 3 months following 89Sr treatment was required. In addition, two studies examining issues of cost with regard to 89Sr treatment were identified.

DATA EXTRACTION

Baseline pain assessment and periodic pain estimates as measured by the Karnofsky index, medication diaries, changes in mobility, sleep patterns, and/or ability to work were the basis for assessment of response. Baseline and periodic complete blood cell counts were the basis for hemotoxicity evaluation.

DATA SYNTHESIS

Palliation and hemotoxicity data were analyzed separately for each study. Some improvement occurred in as many as approximately 80% of patients. Several studies demonstrated complete relief of pain in at least 10% of patients The nadir of platelet and white blood cell counts appears at approximately 4 to 8 weeks following injection, with a partial return to baseline by 12 weeks. As many as 10 injections spaced 3 months apart have been given to some patients with repeated palliative effect and without serious hemotoxicity. Reinjection may be limited by a platelet count below 60 x 10(9)/L, a white blood cell count below 2.4 x 10(9)/L, or the absence of osteoblastic skeletal metastasis as seen on bone scan. Studies examining treatment costs suggest that 89Sr may decrease costs associated with palliation of pain due to metastatic disease.

CONCLUSIONS

As many as 80% of selected patients with painful osteoblastic bony metastases from prostate or breast cancer may experience some pain relief following 89Sr administration. In addition, as many as 10% or more may become pain free. Duration of clinical response may average 3 to 6 months in some cases. Hemotoxicity is mild. A decrease in treatment costs with administration of 89Sr to patients with painful osteoblastic bony metastases from prostate cancer may occur. These observations reflect the preliminary nature of knowledge in this field and point to the need for larger clinical trials of the use of 89Sr palliation.

A multicentre observational study of radionuclide therapy in patients with painful bone metastases of prostate cancer

A multicentre observational study was conducted by the Italian Association of Nuclear Medicine between 1996 and 1998. Twenty-nine Nuclear Medicine Departments participated. The aims of the study were to systematically evaluate the efficacy, toxicity and repeatability of radionuclide therapy of painful bone metastases (RTBM) in a large number of patients and to assess its incidence in patients with prostate cancer. Out of 818 treatments performed with a single i.v. dose of 148 MBq of strontium-89 chloride or 1,295 MBq of rhenium-186 hydroxyethylidene diphosphonate (HEDP), 610 could be evaluated (527 with 89Sr and 83 with 186Re-HEDP). Eighty-one patients received multiple (up to five) RTBM. The total number of retreatments was 100. Patients were followed up for a period of 3-24 months. Results, assessed according to pain relief and consumption of analgesic drugs, were expressed at four levels: 1, no response; 2, mild response; 3, good response; 4, excellent response. Responses were: level 1 in 19%, level 2 in 21.3%, level 3 in 33.3% and level 4 in 26.4% of cases. Retreatments showed significantly (P<0.01) worse responses (48% levels 3+4), in comparison to first RTBM. Duration of palliation was 5.0+/-3.5 months, and was longer in cases of excellent response, in first RTBM, in patients with limited metastases and when 89Sr was used. Better responses were found in cases of limited skeletal disease, under good clinical conditions, when life expectancy exceeded 3 months, and in radiologically osteoblastic or mixed bone lesions. The only statistically significant predictive factor was life expectancy (P<0.001). Flare phenomenon (14.1% of cases) did not correlate with the response. Haematological toxicity (mild to moderate in most cases) mainly affected platelets, and was observed in 25.5% of cases overall and in 38.9% of retreatments. RTBM did not seem to prolong life, though in some cases scintigraphic regression of bone metastases was observed. The two radiopharmaceuticals did not show any statistically significant differences in palliative efficacy and toxicity, either in first RTBM or in retreatments.

Strontium-89 for palliation of pain from bone metastases in patients with prostate and breast cancer

We have used strontium-89 chloride (89Sr) for the palliative treatment of metastatic bone pain. Seventy-six patients (50 males with prostate carcinoma and 26 females with breast cancer) were treated with 148 MBq of 89Sr. Sixteen patients were retreated, receiving two or three doses; the total number of injected doses was consequently 95. The Karnofsky performance status was assessed and pain and analgesia were scored on scales of 9 and 5 points, respectively. The efficacy of 89Sr was evaluated at 3 months of treatment. Three levels of response were considered: good - when there was an increase in the Karnofsky status and a decrease in the pain score (equal to or higher than 4) or analgesic score (equal to or higher than 1); partial - when there was an increase in the Karnofsky status and a decrease in the pain score (2 or 3 points) without significant changes in the analgesic score; no response - if no variation or deterioration in these parameters was observed. In prostate cancer patients, the response was good in 64% of cases and partial in 25%, and there was no response in the remaining 11%. In breast cancer patients, the response was good in 62% of cases and partial in 31%, and there was no response in the remaining 8%. Duration of the response ranged from 3 to 12 months (mean 6 months). In the patients who were retreated the effectiveness was as good as after the first dose of 89Sr. A decrease in the initial leucocyte and platelet counts was observed after the 1st month of treatment, with a gradual partial to complete recovery within 6 months. It is concluded that 89Sr is an effective agent in palliative therapy for metastatic bone pain in patients with prostate or breast carcinoma. If required, retreatment can be administered safely and with the same efficacy as is achieved by the first dose.

Treatment of bone metastases of prostate cancer with strontium-89 chloride: efficacy in relation to the degree of bone involvement

This retrospective study evaluated the toxicity and efficacy of strontium-89 chloride (Metastron, Amersham) in 94 patients with painful bone metastases of prostate cancer (117 injections of 150 MBq) and compared the efficacy of treatment in patients with moderate and extensive bone involvement. The predictive value of flare response with regard to analgesic response was also studied. High-grade leukothrombopenias were observed after only 5% of injections. An improvement in quality of life was obtained in 65% of cases, a decrease in pain in 78% (31% complete response) and a reduction of analgesics in 60%. Efficacy was significantly better for pain decrease (P=0.005) and reduction of analgesics (P=0.018), and response was significantly longer (P<0.0035) in patients with moderate than in patients with extensive bone involvement. The flare response observed in 23% of cases was not predictive of pain response (P=0.919) or reduction of analgesics (P=0.353). A second dose prolonged analgesia in three-quarters of cases without any apparent increase in toxicity. These results confirm the benefit of 89Sr chloride for the treatment of metastatic bone pain and suggest that internal radiotherapy should be started earlier. A bone scan could be proposed at the time of hormonal escape resulting in bone pain, and internal radiotherapy could be initiated when several metastatic foci exist, even if only one is painful. In this way, pain-free follow-up could be prolonged, and the transition to other therapeutic approaches, particularly opioids, delayed.

Strontium induced rickets: metabolic basis

Dietary strontium inhibits both the synthesis of 1,25-dihydroxycholecalciferol and intestinal calcium absorption in vitamin D(3)-repleted chicks. 1,25-Dihydroxycholecalciferol restores calcium absorption to normal, while 25-hydroxycholecalciferol is without effect in the strontium-fed chick. It is suggested that strontium induces rickets by blocking the biosynthesis of 1,25-dihydroxycholecalciferol, the metabolically active form of vitamin D in the intestine.

A bioceramic scaffold composed of strontium-doped three-dimensional hydroxyapatite whiskers for enhanced bone regeneration in osteoporotic defects

Reconstruction of osteoporotic bone defects is a clinical problem that continues to inspire the design of new materials. Methods: In this work, bioceramics composed of strontium (Sr)-doped hydroxyapatite (HA) whiskers or pure HA whiskers were successfully fabricated by hydrothermal treatment and respectively named SrWCP and WCP. Both bioceramics had similar three-dimensional (3D) porous structures and mechanical strengths, but the SrWCP bioceramic was capable of releasing Sr under physiological conditions. In an osteoporotic rat metaphyseal femoral bone defect model, both bioceramic scaffolds were implanted, and another group that received WCP plus strontium ranelate drug administration (Sr-Ran+WCP) was studied for comparison. Results: At week 1 post-implantation, osteogenesis coupled blood vessels were found to be more common in the SrWCP and Sr-Ran+WCP groups, with substantial vascular-like structures. After 12 weeks of implantation, comparable to the Sr-Ran+WCP group, the SrWCP group showed induction of more new bone formation within the defect as well as at the implant-bone gap region than that of the WCP group. Both the SrWCP and Sr-Ran+WCP groups yielded a beneficial effect on the surrounding trabecular bone microstructure to resist osteoporosis-induced progressive bone loss. While an abnormally high blood Sr ion concentration was found in the Sr-Ran+WCP group, SrWCP showed little adverse effect. Conclusion: Our results collectively suggest that the SrWCP bioceramic can be a safe bone substitute for the treatment of osteoporotic bone defects, as it promotes local bone regeneration and implant osseointegration to a level that strontium ranelate can achieve.

Melatonin-micronutrients Osteopenia Treatment Study (MOTS): a translational study assessing melatonin, strontium (citrate), vitamin D3 and vitamin K2 (MK7) on bone density, bone marker turnover and health related quality of life in postmenopausal osteopenic women following a one-year double-blind RCT and on osteoblast-osteoclast co-cultures

This one-year double blind randomized control trial assessed the effects of nightly melatonin, strontium (citrate), vitamin D3 and vitamin K2 (MK7; MSDK) on bone mineral density (BMD) and quality of life (QOL) in postmenopausal osteopenic women (ages 49-75). Compared to placebo, MSDK treatment increased BMD in lumbar spine (4.3%) and left femoral neck (2.2%), with an upward trend for total left hip (p=0.069). MSDK increased serum P1NP levels and reduced bone turnover (CTx:P1NP). Psychometric analyses indicated that mood and sleep quality improved for the MSDK group. MSDK-exposed human mesenchymal stem cells (hMSCs) and human peripheral blood monocytes (hPBMCs) plated in transwells or layered demonstrated increases in osteoblastogenesis, decreases in osteoclastogenesis, increases in OPG (TNFRSF11B) and decreases in RANKL (TNFSF11) levels. In transwell osteoblasts, MSDK increased pERK1/2 (MAPK1/MAPK3) and RUNX2 levels; decreased ERK5 (MAPK7); and did not affect the expression of NFκB (NFKB1) and β1integrin (ITGB1). In layered osteoblasts, MSDK also decreased expression of the metabolic proteins PPARγ (PPARG) and GLUT4 (SLC2A4). In adipose-derived human MSCs, MSDK induced osteoblastogenesis. These findings provide both clinical and mechanistic support for the use of MSDK for the prevention or treatment of osteopenia, osteoporosis or other bone-related diseases.

A comparative study of Sr-incorporated mesoporous bioactive glass scaffolds for regeneration of osteopenic bone defects

Recently, the use of the pharmacological agent strontium ranelate has come to prominence for the treatment of osteoporosis. While much investigation is focused on preventing disease progression, here we fabricate strontium-containing scaffolds and show that they enhance bone defect healing in the femurs of rats induced by ovariectomy.

INTRODUCTION

Recently, the use of the pharmacological agent strontium ranelate has come to prominence for the treatment of osteoporosis due to its ability to prevent bone loss in osteoporotic patients. Although much emphasis has been placed on using pharmacological agents for the prevention of disease, much less attention has been placed on the construction of biomaterials following osteoporotic-related fracture. The aim of the present study was to incorporate bioactive strontium (Sr) trace element into mesoporous bioactive glass (MBG) scaffolds and to investigate their in vivo efficacy for bone defect healing in the femurs of rats induced by ovariectomy.

METHODS

In total, 30 animals were divided into five groups as follows: (1) empty defect (control), (2) empty defects with estrogen replacement therapy, (3) defects filled with MBG scaffolds alone, (4) defects filled with MBG + estrogen replacement therapy, and (5) defects filled with strontium-incorporated mesopore-bioglass (Sr-MBG) scaffolds.

RESULTS

The two groups demonstrating the highest levels of new bone formation were the defects treated with MBG + estrogen replacement therapy and the defects receiving Sr-MBG scaffolds as assessed by μ-CT and histological analysis. Furthermore, Sr scaffolds had a reduced number of tartrate-resistant acid phosphatase-positive cells when compared to other modalities.

CONCLUSION

The results from the present study demonstrate that the local release of Sr from bone scaffolds may improve fracture repair. Future large animal models are necessary to investigate the future relationship of Sr incorporation into biomaterials.

Effects of low chronic doses of ionizing radiation on antioxidant enzymes and G6PDH activities in Stipa capillata (Poaceae)

Stipa capillata (Poaceae) seeds were harvested from a control area (displaying a gamma dose rate of 0.23 micro Sv h(-1)) (C plants) and from two contaminated areas (5.4 and 25 micro Sv h(-1)) on the Semipalatinsk nuclear test site (SNTS) in Kazakhstan. The plants were grown for 124 d in a greenhouse under controlled conditions and exposed to three different treatments: (0) control; (E) external gamma irradiation delivered by a sealed 137Cs source with a dose rate of 66 micro Sv h(-1); (E+I) E treatment combined with internal beta irradiation due to contamination by 134Cs and 85Sr via root uptake from the soil. The root uptake led to a contamination of 100 Bq g(-1) for 85Sr and 5 Bq g(-1) for 134Cs (of plant dry weight) as measured at harvest. The activity of SOD, APX, GR, POD, CAT, G6PDH, and MDHAR enzymes was measured in leaves. Under (0) treatment, all enzymes showed similar activities, except POD, which had higher activity in plants originating from contaminated areas. Treatment (E) induced an enhancement of POD, CAT, GR, SOD, and G6PDH activities in plants originating from contaminated areas. Only control plants showed any stimulation of APX activity. Treatment (E+I) had no significant effect on APX, GR, CAT, and POD activities, but MDHAR activity was significantly reduced while SOD and G6PDH activities were significantly increased. The increase occurred in plants from all origins for SOD, with a greater magnitude as a function of their origin, and it occurred only in plants from the more contaminated populations for G6PDH. This suggests that exposure to a low dose rate of ionizing radiation for almost a half century in the original environment of Stipa has led to natural selection of the most adapted genotypes characterized by an efficient induction of anti-oxidant enzyme activities, especially SOD and G6PDH, involved in plant protection against reactive oxygen species.

Strontium-89 chloride in the treatment of bone metastases from breast cancer

Sixty-four patients with painful metastatic breast cancer in bone were treated with 2 MBq/kg of strontium-89 chloride as a single intravenous injection. Patients were followed with records of medication, hematology parameters, serial bone and Sr-89 bremsstrahlung images and with a point pain score scale (10-0). The response was assessed during a 6-month period of follow-up. Fifty-two of 64 patients (81%) showed at least a moderate improvement. Eighteen out of the 52 responders showed a dramatic decrease in bone pain (35%), 21 (40%) presented a satisfactory response and in 13 cases (25%) the response was moderate. Only 12 patients (19%) from the whole group did not feel any improvement on pain palliation. A statistically significant decrease of pretreatment levels of platelets and leukocyte counts was observed after 4-6 weeks of therapy in 50 (70%) patients. Although most patients showed no change in their bone scans after 3 months of treatment, an obvious improvement was observed in 3 of them. Furthermore no additional painful metastases on their bone scintigraphic images were observed. The selective strontium-89 local uptake in metastatic sites was also confirmed directly by bremsstrahlung scans which were absolutely comparable to the respective 99mTc bone scans. Precautions have been taken against Sr-89 contamination from the patients' blood or excretions.

Strontium-89 (Metastron) and the bisphosphonate olpadronate reduce the incidence of spinal cord compression in patients with hormone-refractory prostate cancer metastatic to the skeleton

Spinal cord compression (SCC) is a devastating complication of metastatic cancer. We investigated the potential beneficial effect of two palliative therapies--strontium-89 (Metastron) and the nitrogen-containing bisphosphonate olpadronate--on the incidence of SCC in hormone-refractory prostate cancer (HRPC) metastatic to the skeleton. We retrospectively studied 415 patients with histologically proven prostate cancer who underwent bone scintigraphy at the time of diagnosis and were followed up at the Leiden University Medical Center between 1990 and 1999. Medical or surgical castration was undertaken in 172 patients with evidence for skeletal metastases. Within 2 years, 147 of these patients (85%) developed HRPC associated with severe progressive bone pain. Palliative treatment was given to 131 patients in the form of local radiotherapy ( n=10), 89Sr ( n=46) or intravenous olpadronate ( n=66), with ( n=57) or without ( n=9) maintenance oral olpadronate. Nine patients received both 89Sr and olpadronate at various intervals. Sixteen patients who did not receive any of these treatments were used as historical controls. There was no significant difference in baseline characteristics between treatment modalities. The incidence of SCC was 17% in the whole group, and highest in controls receiving no palliation (50%). None of the patients treated with local radiotherapy, only 4% of patients receiving 89Sr and 21% of patients given olpadronate developed this complication. Our findings suggest a significant reduction in SCC in patients with symptomatic HRPC metastatic to the skeleton who receive palliative therapies. Local radiotherapy completely prevents the incidence of SCC, 89Sr leads to an important decrease in this complication and olpadronate induces a significant, albeit smaller decrease in the incidence of SCC. The use of these agents opens new avenues in the difficult management of patients with advanced prostate cancer who are most at risk of developing SCC.

A novel topical formulation containing strontium chloride significantly reduces the intensity and duration of cowhage-induced itch

The aim of this double-blinded, vehicle-controlled study was to test the antipruritic efficacy of topical strontium to relieve a nonhistaminergic form of itch that would be clinically relevant for chronic pruritic diseases. Itch induced with cowhage is mediated by PAR2 receptors which are considered to play a major role in itch of atopic dermatitis and possibly other acute and chronic pruritic conditions. The topical strontium hydrogel formulation (TriCalm®) was tested in a head-to-head comparison with 2 common topical formulations marketed as antipruritics: hydrocortisone and diphenhydramine, for their ability to relieve cowhage-induced itch. Topically-applied strontium salts were previously found to be effective for reducing histamine-induced and IgE-mediated itch in humans. However, histamine is not considered the critical mediator in the majority of skin diseases presenting with chronic pruritus. The current study enrolled 32 healthy subjects in which itch was induced with cowhage before and after skin treatment with a gel containing 4% SrCl2, control vehicle, topical 1% hydrocortisone and topical 2% diphenhydramine. Strontium significantly reduced the peak intensity and duration of cowhage-induced itch when compared to the control itch curve, and was significantly superior to the other two over-the-counter antipruritic agents and its own vehicle in antipruritic effect. We hereby show that a 4% topical strontium formulation has a robust antipruritic effect, not only against histamine-mediated itch, but also for non-histaminergic pruritus induced via the PAR2 pathway, using cowhage.

Effectiveness of desensitizing agents

This study was conducted to evaluate the efficacy of desensitizing agents for the treatment of dentin hypersensitivity. Seventy-five hypersensitive teeth in 10 patients were studied. These were divided into five groups of 15 hypersensitive teeth: group I, control (triple distilled water); group II, 10% strontium chloride; group III, 5% potassium nitrate; group IV, 2% sodium fluoride; and group V, 40% formalin. The stimulus used to test thermal sensitivity was cold water at 15 degrees C, 10 degrees C, 5 degrees C, and 0 degrees C applied on every alternate day for 10 days. Results showed that 10% strontium chloride solution, 2% sodium fluoride solution, and 40% formalin solution significantly reduced dentin hypersensitivity, whereas a 5% solution of potassium nitrate did not.

Strontium-89 chloride (Metastron) for palliative treatment of bony metastases. The University of Minnesota experience

Strontium-89 chloride (Metastron) is an FDA-approved treatment for palliation of cancer pain. We evaluated blood count changes and pain relief in 28 patients with widespread painful bony metastasis treated with strontium-89 at the University of Minnesota Hospital and Clinics. Eighteen patients had prostate cancer (all hormone-refractory cancer), seven patients had breast cancer, and three patients had lung cancer, all previously treated with either radiation, chemotherapy, or a combination of the two. Serial blood counts were performed weekly up to 8 weeks and at 12 weeks after administering Metastron. Pain scale and blood values were monitored simultaneously. The mean baselines of hemoglobin (Hgb), white blood count (WBC), and platelets (Plts) were 11.4, 5900, and 258,000, respectively. The mean dose of Metastron was 3 mCi (range 2.2-4.4). The median time (range) to nadir was about 6 weeks. The percentage reductions relative to baseline were 32% (range 0-72%) for WBC; 14% (range 0-50%) for Hgb; 15% (range 0-47%) for the red blood cell (RBC) count; and 40% (range 0-85%)for Plts. We did not find a close relationship among the baseline blood count, reduction of subsequent blood counts, or previously irradiated active bone marrow volume. The median time of survival was 23 weeks (range 2-66 weeks). At 12 weeks, 29% of patients had moderate to dramatic improvement of pain, 32% had some relief of pain, and 50% had no improvement in pain. Thirty-two percent of the treated patients required additional palliative external beam radiation to their bony lesions within the study period. Our results show that Metastron for palliation for bony metastases should be used with caution because of moderate to severe bone marrow toxicity, especially in platelets, associated with its use. Careful evaluation of patients given Metastron is needed to assess accurately its full benefit.

Use of strontium for bovine oocyte activation

Strontium efficiently activates mouse oocytes, however, there is limited information on its use in cattle. Thus, the objective of this study was to establish a suitable protocol for activating bovine oocyte with strontium. For pronuclear development, the absence of calcium and magnesium in the activation medium (TALP) with 10 and 50 mM strontium (34.4 and 53.1%, respectively) was superior to the complete TALP (6.5 and 19.4%, respectively). In all activation media, better results were observed with 25 and 50 mM strontium (21.9-53.1 and 19.4-53.1%, respectively). Incubation for 4 h promoted similar results in all strontium concentrations. However, strontium at 15, 20, and 25 mM for 6 and 8 h (40.7, 46.7, and 48.3%, and 29.3, 48.3, and 40.7%, respectively) were superior to control (15.5 and 10%, respectively). After in vitro maturation for 26 h, strontium (S; 20 mM in Ca2+- and Mg2+-free TALP for 6 h), ionomycin+strontium (IS), and strontium+ionomycin (SI) (60, 63.3, and 65%, respectively) were similar in pronuclear development and superior to ionomycin (I; 5 microM for 5 min; 36.7%). In treatments S and I, only 1 PN zygotes were observed. In treatment S, most of them had 1 and 2 PB (35.7 and 60.7%, respectively), and in treatment I, 0, 1, and 2 PB (14.3, 57.1, and 28.6%, respectively). Most of the zygotes in treatment IS and SI were 1 PN 2 PB (77.4 and 61.6%, respectively). The number of oocytes with clusters of cortical granules was similar in all treated groups (11-29%). Cortical granule exocytosis in treatment IS (68%) was similar to S (54%) and superior to I, SI, and control (27, 45, and 5.0%, respectively). Cleavage and blastocyst rates were similar for S, I, IS, and SI treatments (61.7-76.7, and 8.3-13.3%, respectively) and the same was observed for ICM, TE, and total cell number, and ICM/total cell ratio (22-25, 64-69, and 86-95, and 0.26-0.27). In conclusion, strontium may be efficiently applied for bovine oocyte activation at 20 mM in Ca2+- and Mg2+-free TALP medium for 6 h.

Strontium release from Sr2+-loaded bone cements and dispersion in healthy and osteoporotic rat bone

Drug functionalization of biomaterials is a modern and popular approach in biomaterials research. Amongst others this concept is used for the functionalization of bone implants to locally stimulate the bone healing process. For example strontium ions (Sr²⁺) are administered in osteoporosis therapy to stimulate bone growth and have recently been integrated into bone cements. Based on results of different analytical experiments we developed a two-phase model for the transport of therapeutically active Sr²⁺-ions in bone in combination with Korsmeyer-Peppas kinetics for the Sr²⁺ release from bone cement. Data of cement dissolution experiments into water in combination with inductively coupled plasma mass spectrometry (ICP-MS) analysis account for dissolution kinetics following Noyes-Whitney rule. For dissolution in α-MEM cell culture media the process is kinetically hindered and can be described by Korsmeyer-Peppas kinetics. Time of flight secondary ion mass spectrometry (ToF-SIMS) was used to determine the Sr²⁺ diffusion coefficient in healthy and osteoporotic trabecular rat bone. Therefore, bone sections were dipped in aqueous Sr²⁺-solution by one side and the Sr²⁺-profile was measured by classical SIMS depth profiling. The Sr²⁺ mobility can be described by a simple diffusion model and we obtained diffusion coefficients of (2.28±2.97)⋅10^-12cm²/s for healthy and of (1.55±0.93)⋅10^-10cm²/s for osteoporotic bone. This finding can be explained by a different bone nanostructure, which was observed by focused ion beam scanning electron microscopy (FIB-SEM) and transmission electron microscopy (TEM). Finally, the time and spatially resolved drug transport was calculated by finite element method for the femur of healthy and osteoporotic rats. The obtained results were compared to mass images that were obtained from sections of in vivo experiments by ToF-SIMS. The simulated data fits quite well to experimental results. The successfully applied model for the description of drug dispersion can help to reduce the number of animal experiments in the future.

Titanium and strontium-doped phosphate glasses as vehicles for strontium ion delivery to cells

This study investigated the use of a Ti-containing quaternary phosphate glass system P(2)O(5)-Na(2)O-CaO-TiO(2) as a vehicle for strontium ion delivery to cells. Four glass compositions were manufactured: 0.5P(2)O(5)-0.15Na(2)O-0.05TiO(2)-(0.3 - x)CaO-xSrO (x = 0, 0.01, 0.03, and 0.05). Structural characterization revealed that sodium calcium phosphate is the dominant phase in all the glasses. Degradation studies demonstrated highly linear glass degradation, with Sr-containing glasses degrading at higher rates than the Sr-free glass. Biocompatibility studies using MG63 cells showed that the Sr-containing glasses possess excellent cell attachment and growth, particularly over short periods (~4 days).

Surface treatment of injectable strontium-containing bioactive bone cement for vertebroplasty

A novel injectable bioactive bone-bonding cement (SrHAC) composed of strontium-containing hydroxyapatite (Sr-HA) as the inorganic filler and bisphenol A diglycidylether dimethacrylate (Bis-GMA) as the organic matrix for vertebroplasty was developed previously. In this study, the Sr-HA powders were surface treated with methyl methacrylate (MMA) to improve the interface integration of the two phases. After surface treatment, the compression strength and Young's modulus, which were tested after immersion in distilled water at 37 degrees C for 24 h according to ISO 5833, were increased by 68.65 % (p <.001) and 31.02% (p <.001), respectively. The bending strength and bending stiffness of the bioactive bone cement were significantly improved by 54.44% (p <.001) and 83.90% (p <.001). In addition, the handling property of the cement was also enhanced. In vitro biomechanical testing showed that the stiffness of the fractured spine recovered to 82.5% (p <.01) of the intact condition after cementation with surface-treated SrHAC. The failure load of the spine cemented with original and MMA-treated SrHAC improved by 14.25% (p <.05) and 46.91% (p <.05) in comparison with the fractured spines. Results from this study revealed that the MMA-treated SrHAC has a better mechanical effect for orthopedic applications.

Systemic radionuclide therapy in pain palliation

Several radiopharmaceuticals were investigated to determine their efficacy and toxicity in the palliation of painful bone metastases. Data on the influence of rhenium-188 hydroxyethylidene diphosphonate (188Re-HEDP), rhenium-186 hydroxyethylidene diphosphonate (186Re-HEDP), and strontium-89 (89Sr) on pain symptoms, quality of life, and bone-marrow function were obtained in 64 patients with breast and prostate cancer. Thirty-one patients were treated with 188Re-HEDP (3194 +/- 387 MBq), 15 patients with 186Re-HEDP (1358 +/- 158 MBq), and 18 patients with 89Sr (152 +/- 19 MBq). The 188Re-HEDP group included six breast cancer patients and 25 prostate cancer patients; the 186Re-HEDP group included three breast cancer patients and 12 prostate cancer patients; and the 89Sr group included three breast cancer patients and 15 prostate cancer patients. All subjects participated in an interview using a standardized sets of questions before and after the 12-week term of therapy. Blood counts were taken weekly for six weeks and after 12 weeks. Results showed that 77 percent of patients reported pain relief after treatment with 188Re-HEDP, 67 percent after treatment with 186Re-HEDP, and 72 percent after treatment with 89Sr. Sixteen percent of patients treated with 188Re-HEDP, 13 percent treated with 186Re-HEDP, and 17 percent treated with 89Sr were able to discontinue their analgesics and were pain-free. Patients described an improvement on Karnofsky performance status (KPS) from 73 +/- 7 percent to 85 +/- 8 percent 12 weeks after 188Re-HEDP (p < 0. 05), from 72 +/- 13 percent to 79 +/- 12 percent after 186Re-HEDP (p = 0.251), and from 62 +/- 14 percent to 69 +/- 16 percent after 89Sr (p = 0.415). Only three patients undergoing 188Re-HEDP therapy, one undergoing 186Re-HEDP therapy, and three undergoing 89Sr therapy had thrombocytopenia (platelet count below 100 x 10(3)/microl) following treatment. The maximum nadir of platelet and leukocyte counts was observed between the second and fifth week after treatment for all radionuclides and was reversible within 12 weeks. The nadir was earlier for 188Re-HEDP with a shorter physical half-life compared with 89Sr. There were no significant differences in bone marrow toxicity (p = 0.123-0.421). Results of this study indicate that all evaluated radiopharmaceuticals were effective in pain palliation without induction of severe side effects. The increase in KPS after 188Re-HEDP was the only statistically significant finding (p = 0.001).

Strontium nitrate suppresses chemically-induced sensory irritation in humans

Skin care products are complex formulations that may cause sensory irritation symptoms, characterized by stinging, burning, and itching. Substances capable of counteracting sensory irritation are of great practical interest. Strontium salts have been demonstrated to inhibit sensory irritation and inflammation when applied topically. In this double-blind study, we evaluated the efficacy of strontium nitrate in reducing chemically-induced skin sensory irritation in 8 subjects. In a random order, 20% strontium nitrate in 70% glycolic acid (pH=0.6) (mixture) was applied to the volar aspect of the forearm and a positive control (70% glycolic acid, pH=0.6) to the contralateral forearm. The irritation sensation was evaluated each min for the first 20 min after topical application using a scale from 0-4. The duration of the irritation sensation in min was also recorded. Strontium nitrate mixed with glycolic acid, in comparison with glycolic acid alone, markedly (p<0.01) shortened the duration of the irritation sensation from 24.4+/-4.1 (mean+/-SEM) min to 8.9+/-3.7 (mean+/-SEM) min, and significantly (p<0.05) reduced the mean magnitude of the irritation sensation at all time points (overall). The study demonstrated that strontium nitrate potently suppresses the sensation of chemically-induced irritation.

Dental caries and strontium concentration in drinking water and surface enamel

We investigated the possible cariostatic effect of strontium in the absence of effective amounts of fluoride by relating the DMFT index of the population to the strontium and fluoride concentrations in drinking water and enamel surfaces. The epidemiological survey was conducted in two neighboring districts in the northwest part of Greece, involving 582 children ranging in age from 11 to 14. The average DMFT values were 5.26 in the high-strontium (2.9-7 ppm Sr) area and 6.95 in the low-strontium (0.2-1.3 ppm Sr) area, while fluoride was low (less than 0.06 ppm) in both districts. Further, the average strontium concentration in surface enamel was higher in the high-strontium area.

Human pharmacokinetics of orally administered strontium

Pharmacokinetics of orally administered SrCl2 (2.5 mmol) were studied in six healthy male volunteers. In the overall plasma concentration time (C-t) curves, two absorption phases were observed due to two dominant intestinal absorption loci. A method was devised to obtain separately the plasma C-t curves associated with each of the two absorption loci (curve 1 and curve 2). These curves and the overall plasma C-t curve were analyzed with a nonlinear estimation program (PCNONLIN). Pharmacokinetic parameters (mean +/- SD, n = 6) calculated from the overall curve were as follows: peak plasma concentration (Cmax) 3.55 +/- 1.22 micrograms/ml and area under the plasma C-t curve (AUC affinity) 9138 +/- 1930 micrograms.min/ml. The pharmacokinetic parameters calculated from curve 1 were as follows: terminal plasma elimination half-life time 47.3 +/- 7.9 hour, the plasma elimination half-life time of the preceding phase 5.2 +/- 3.3 hour, Cmax 1 3.09 +/- 0.95 micrograms/ml, the first-order absorption rate constant for absorption locus 1 (Ka,1) 5.7 +/- 1.2 * 10(-2) minute-1 and the time lag (tlag,1) 11.7 +/- 7.9 minute. In three of the subjects the pharmacokinetic parameters of absorption locus 2 could be evaluated: Ka,2 = 4.6 +/- 0.4 * 10(-2) minute-1, tlag,2 = 77.3 +/- 4.0 minute, tmax,2 = 153 +/- 16 minute, Cmax,2 = 0.9 +/- 0.4 micrograms/ml and AUC 2 affinity = 1204 +/- 565 micrograms. minute/ml. and AUC2 affinity = 0.14, indicating that 14% of the absorbed dose was absorbed via the second locus.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption of strontium from the gastrointestinal tract into plasma in healthy human adults

The radioactive isotopes of strontium have always been a major concern in radiation protection. Currently, radiostrontium is of interest for evaluation of the health effects of the Chernobyl accident and for epidemiological studies in populations exposed to releases from the Mayak nuclear facilities in Russia. Ingestion is one of the most important exposure pathways involving radioactive strontium. The main sources of published data on the fraction of the ingested strontium that is transferred to plasma (f1) are summarized. For some of these studies, the original data had to be reanalyzed and a new iterative method to account for the elimination in feces of strontium of endogenous origin (i.e., that was absorbed to blood and has already been returned into feces) was employed. Data indicate no significant dependence of the absorbed fraction on sex or age at exposure within the adult group, but absorption of strontium is reduced if the intake of stable calcium is very high and is enhanced if the intake of calcium is very low. The probability distribution function of f1 values is well represented by a lognormal curve with a geometric mean of 22.3% and a geometric standard deviation of 1.44 (95% confidence interval 10.9% to 45.6%, or about a factor of 2 around the geometric mean). This distribution can be considered representative for the variability of the f1 values in a population of healthy adults.