Urinary biomarker of strontium exposure is positively associated with semen quality among men from an infertility clinic.

Experimental studies have shown that nonradioactive strontium (Sr), in the form of Sr2+, have a positive effect on semen quality, but human evidence is lacking. This study aimed to examine the associations between nonradioactive Sr exposure and semen quality in Chinese men (n = 394). We recruited men who presented at an infertility clinic in Wuhan, China to seek for semen parameter analyses. Urinary Sr concentration as an exposure biomarker was measured using inductively coupled plasma mass spectrometer. We estimated the associations between urinary Sr concentrations and semen parameters using multivariable logistic and linear regression models. In multivariable linear regressions models, positive dose-response associations were estimated for sperm concentration, motility, and count across increasing urinary Sr quartiles (all p for trends<0.05), and the consistent positive associations were also observed for urinary Sr concentration modeled as a continuous exposure. In multivariable logistic models, decreased risks of below-reference sperm concentration, motility, and count were also estimated across increasing urinary Sr quartiles (all p for trends<0.05). Our results suggest that nonradioactive Sr exposure may have a beneficial effect on semen quality, but more investigations are warranted to confirm the results.

[Distribution of rubidium, cesium, beryllium, strontium, and barium in blood and urine in general Chinese population].

OBJECTIVE: To investigate the distribution of rubidium (Rb), cesium (Cs), beryllium (Be), strontium (Sr), and barium (Ba) in blood and urine in general Chinese population. METHODS: A total of 18 120 subjects aged 6~60 years were enrolled from 24 regions in 8 provinces in Eastern, Central, and Western China from 2009 to 2010 based on the method of cluster random sampling. Questionnaire survey was conducted to collect the data on living environment and health status. Blood and urine samples were collected from these subjects, and the levels of Rb, Cs, Be, Sr, and Ba in these samples were determined by inductively coupled plasma mass spectrometry. The distribution of these elements in blood and urine in male or female subjects living in different regions was analyzed statistically. RESULTS: In the general Chinese population, the concentration of Be in the whole blood was below the detection limit (0.06 µg/L); the geometric mean (GM) of Ba in the whole blood was below the detection limit (0.45 µg/L), with the 95th percentile (P95)of 1.37 µg/L; the GMs (95% CI)of Rb, Cs, and Sr in the whole blood were 2 374(2 357~2 392) µg/L, 2.01 (1.98~2.05) µg/L, and 23.5 (23.3~23.7) µg/L, respectively; in males and females, the GMs (95%CI)of blood Rb, Cs, and Sr were 2 506 (2 478~2 533) µg/L and 2 248 (2 227~2 270) µg/L, 1.88 (1.83~1.94) µg/L and 2.16 (2.11~2.20) µg/L, and 23.4 (23.1~23.7) µg/L and 23.6 (23.3~23.9) µg/L, respectively(P<0.01, P>0.05, and P>0.05). In the general Chinese population, the GM of urine Be was below the detection limit (0.06 µg/L), while the GMs (95%CI)of urine Rb, Cs, Sr, and Ba were 854 (836~873) µg/L, 3.65 (3.56~3.74) µg/L, 39.5 (38.4~40.6) µg/L, and 1.10 (1.07~1.12) µg/L, respectively; in males and females, the GMs (95%CI)of urine Rb, Cs, Sr, and Ba were 876 (849~904) µg/L and 832 (807~858) µg/L, 3.83 (3.70~3.96) µg/L and 3.47 (3.35~3.60) µg/L, 42.5 (40.9~44.2) µg/L and 36.6 (35.1~38.0) µg/L, and 1.15 (1.12~1.19) µg/L and 1.04 (1.01~1.07) µg/L, respectively (all P< 0.01). Correlation analyses showed that there were weak correlations between blood Rb and urine Rb (r=0.197)and between blood Sr and urine Sr (r=0.180), but a good correlation between blood Cs and urine Cs (r=0.487). CONCLUSION: The levels of Rb, Cs, Be, Sr, and Ba in the general Chinese population are similar to those reported in other countries, and there is a significant difference in the concentration of each element among the populations living in different regions, as well as significant differences in blood Rb, urine Rb, urine Cs, urine Sr, and urine Ba between males and females.

A simple assessment of the effect of strontium on the urinary excretion of calcium in Sprague Dawley rats.

This study was aimed at investigating the impact of varying concentrations of strontium (Sr) on calcium (Ca) excretion via the urine and determine its impact on kidney stone formation. Twenty adult male Sprague Dawley rats weighing between 200 and 300 g were selected. The rats were randomly divided into four groups of five. One group was used as a control group while the other three groups were experimental. The diet of the rats was modulated over a 12 week period to investigate the impact of Sr on the urinary excretion of Ca. Urinary samples were collected every 2 weeks from the rats. The rats were fed water ad libitum. After the study the rats were euthanised and their kidneys harvested. Urine and kidney samples from the rats were analysed using Total Reflection X-Ray Fluorescence (TXRF). In the urine excretion of Ca increased with increased intake of Sr in the diet. Sr excretion via the urine also increased with increased dietary intake. There was a correlation of 0.835 at the significance level of 0.01 between Ca and Sr in the urine. However, for the kidneys, the varying concentration of Sr did not impact the retention of Ca in the kidneys. There was increased retention of Sr in the kidneys with increased dietary intake. In this study an increase of Sr in the diet resulted in an increase in urinary excretion of Ca.

Urinary strontium and the risk of breast cancer: a case-control study in Guangzhou, China.

Strontium has been widely used in industries like electronic and pharmacy. It has a carcinogenic potential, however, and no study has been conducted to evaluate its effects on cancer risk. The aim of this study was to explore the possible association between strontium and breast cancer risk in a case-control study including 240 incident invasive breast cancer patients and 246 age-matched controls. We measured the urinary concentrations of strontium by inductively coupled plasma mass spectrometry, and conducted face-to-face interviews to obtain information on potential breast cancer risk factors. Multivariable analysis was used to estimate the association. Creatinine-adjusted levels [median (25th, 75th) µg/g] of strontium were 155.59 (99.05, 230.70) in the breast cancer patients and 119.62 (81.97, 163.76) in the controls. Women in the highest tertile of strontium showed 124% increased risk of breast cancer, when compared with those in the lowest tertile after adjustment for the potential risk factors [OR (95% CI): 2.24 (1.42-3.81)]. This association was particularly strong for HER2 positive breast cancer [OR (95% CI): 10.92 (3.53-33.77)], and only occurred among premenopausal women. These results suggest a potential role of strontium in the development of breast cancer and urge further studies on the environmental contamination and the physiological and pathological mechanisms of strontium.

Association of Urinary Strontium Levels with Pregnancy-induced Hypertension.

Pregnancy-induced hypertension (PIH), including gestational hypertension and preeclampsia, accounts for the majority of maternal and perinatal morbidity and mortality. Strontium (Sr) has been recently associated with preeclampsia in a small group of women; however, the role of Sr in PIH is not fully understood and warrants further investigation. In this study, we examined the association between urinary Sr levels and PIH, and assessed the effect of maternal age on the association. Urinary Sr concentrations were measured in 5423 pregnant women before delivery by inductively coupled plasma mass spectrometry (ICP-MS). Logistic regression analysis adjusting for potential confounders was applied to explore the association between Sr and PIH, and to evaluate the Sr-PIH relationship stratified by maternal age. Among the participants, 200 (3.83%) women were diagnosed with PIH. Compared with non-PIH women, women who developed PIH had lower urinary Sr concentrations (131.26 vs. 174.98 µg/L creatinine, P<0.01). With the natural log-transformed urinary creatinine-standardized Sr concentrations increasing, the risk of PIH decreased significantly [adjusted OR=0.60 (95%CI: 0.51, 0.72)]. Furthermore, the significant association of Sr with PIH was found among women under 35 years (P<0.01). Our finding suggested that Sr may play a potential protective role in the pathogenesis of PIH, especially among young pregnant women under 35 years old.

Effect of a maximal exercise test on serum and urinary concentrations of magnesium, phosphorous, rubidium and strontium in athletes.

AIM: This study aims to determine the changes induced by a maximal exercise test until exhaustion on the serum and urinary concentrations of Magnesium (Mg), Phosphorous (P), Rubidium (Rb) and Strontium (Sr) in athletes (AG) and sedentary students (SG). METHODS: Fifty subjects participated in the study divided into two groups. In AG there were twenty-five male athletes and in SG there were twenty-five male sedentary students. Both groups performed an exercise test until exhaustion, starting at 8 or 10 km/h respectively, and increasing the speed at 1 km/h every 400 m. Serum and urine samples were obtained from all participants before and after the test. RESULTS: Regarding the basal status, AG showed lower values of Mg in serum (p < 0.05) and urine (p < 0.01), but higher concentrations of serum P (p < 0.05) in comparison to SG. Comparing the pre and post-test values, corrected or non-corrected for hemoconcentration in serum and for creatinine in urine, AG showed a decrease in serum Mg (p < 0.05), in serum P (p < 0.01) and in urinary Sr (p < 0.01) while an increase was observed in urinary P (p < 0.05) and in urinary Rb (p < 0.05). CONCLUSIONS: It can be concluded that a treadmill test until exhaustion leads to changes in serum and urinary concentrations of minerals in both AG and SG males. This may reflect an adaptive response of the body to overcome the physical stress and, in some cases, to avoid loss of these elements.

Association of plasma and urine metals levels with kidney function: A population-based cross-sectional study in China.

OBJECTIVES: Although environmental exposure to multiple metals is common, epidemiological studies on the associations of exposure to 23 metals with kidney function have not been analyzed. We aimed to investigate the associations of 23 metals levels with renal function. METHODS: We conducted a cross-sectional study in four rural regions of Hunan province. Plasma and urine metals levels were determined by inductively coupled plasma mass spectrometer (ICP-MS). Two-level logistic regression was used to investigate the associations of metals levels with estimated glomerular filtration rate (eGFR) with adjustment for confounding factors. We conducted a sensitivity analysis of the results using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. RESULTS: A total of 3553 participants completed the investigation. Five metals (plasma arsenic and molybdenum; urine copper, rubidium, and strontium) were identified to be significantly associated with renal function. Participants in the highest quartile of plasma arsenic and molybdenum were at 17.95 (95% CI: 6.35-50.76) and 24.23 (95% CI: 7.42-79.19) fold risk of abnormal eGFR, respectively, compared with the lowest quartile. The highest quartiles of urine copper, rubidium, and strontium were associated with 3.70 (95% CI:1.92-7.14), 0.16 (95% CI:0.07-0.37) and 0.08 (95% CI: 0.03-0.21) fold risk of abnormal eGFR. The sensitivity analysis revealed that plasma arsenic, molybdenum and urine copper, rubidium and strontium levels retained similar associations with abnormal eGFR. CONCLUSION: Plasma arsenic and molybdenum, and urine copper are risk factors for abnormal renal function, while urine rubidium and strontium are protective factors for renal function.

Intestinal Calcium Absorption among Hypercalciuric Patients with or without Calcium Kidney Stones.

BACKGROUND AND OBJECTIVES: Idiopathic hypercalciuria is a frequent defect in calcium kidney stone formers that is associated with high intestinal calcium absorption and osteopenia. Characteristics distinguishing hypercalciuric stone formers from hypercalciuric patients without kidney stone history (HNSFs) are unknown and were explored in our study. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We compared 172 hypercalciuric stone formers with 36 HNSFs retrospectively selected from patients referred to outpatient clinics of the San Raffaele Hospital in Milan from 1998 to 2003. Calcium metabolism and lumbar bone mineral density were analyzed in these patients. A strontium oral load test was performed: strontium was measured in 240-minute urine and serum 30, 60, and 240 minutes after strontium ingestion; serum strontium concentration-time curve and renal strontium clearance were evaluated to estimate absorption and excretion of divalent cations. RESULTS: Serum strontium concentration-time curve (P<0.001) and strontium clearance (4.9±1.3 versus 3.5±2.7 ml/min; P<0.001) were higher in hypercalciuric stone formers than HNSFs, respectively. The serum strontium-time curve was also higher in hypercalciuric stone formers with low bone mineral density (n=42) than in hypercalciuric stone formers with normal bone mineral density (n=130; P=0.03) and HNSFs with low (n=22; P=0.01) or normal bone mineral density (n=14; P=0.02). Strontium clearance was greater in hypercalciuric stone formers with normal bone mineral density (5.3±3.4 ml/min) than in hypercalciuric stone formers and HNSFs with low bone mineral density (3.6±2.5 and 3.1±2.5 ml/min, respectively; P=0.03). Multivariate regression analyses displayed that strontium absorption at 30 minutes was positively associated calcium excretion (P=0.03) and negatively associated with lumbar bone mineral density z score (P=0.001) in hypercalciuric stone formers; furthermore, hypercalciuric patients in the highest quartile of strontium absorption had increased stone production risk (odds ratio, 5.06; 95% confidence interval, 1.2 to 20.9; P=0.03). CONCLUSIONS: High calcium absorption in duodenum and jejunum may expose hypercalciuric patients to the risk of stones because of increased postprandial calcium concentrations in urine and tubular fluid. High calcium absorption may identify patients at risk of bone loss among stone formers.

[Determination of the contents of fourteen elements in urine of Xinjiang kuitun fluorine poisoning and arsenic-fluoride poisoning patients by ICP-AES].

A method of determining the contents of K, Na, Ca, Mg, P, Zn, Al, Ba, Co, Cu, Ni, Sr, Cr and Ti, fourteen elements, in urine of Xinjiang Kuitun fluorine poisoning and arsenic-fluoride poisoning patients was developed. The operation conditions of ICP-AES, and the lowest test concentration, precision and linear ranges were studied. The relative standard deviation of the method was 0.24%-2.47% (n=10), the average recoveries were 90.4%-00.5%. The contents of K and Na in urine of fluorine poisoning and arsenic-fluoride poisoning patients were higher than those of healthy contrast group. The contents of Ba, Co, Cu, Ni and Cr in the urine of arsenic-fluoride poisoning patients were higher than those of fluorine poisoning patients and healthy contrast group (P < 0.05). The contents of P, Ca, Mg, Zn, Al, Sr and Ti do not have statistic significance (P > 0.05). The method was sensitive, simple and accurate. The experiment data was reliable.

Low Serum Testosterone Levels Are Associated with Elevated Urinary Mandelic Acid, and Strontium Levels in Adult Men According to the US 2011-2012 National Health and Nutrition Examination Survey.

BACKGROUND: Little is known regarding the effects of environmental exposure of chemicals on androgenic system in the general population. We studied 5,107 subjects included in the National Health and Nutrition Examination Survey (2011-2012). METHODS: Urinary, serum, and blood levels of 15 subclasses comprising 110 individual chemicals were analyzed for their association with serum testosterone levels. The subjects were divided into high and low testosterone groups according to the median testosterone concentration (374.51 ng/dL). Odds ratios (ORs) of individual chemicals in association with testosterone were estimated using logistic regression after adjusting for age, ethnicity, cotinine, body mass index, creatinine, alcohol, and the poverty income ratio. RESULTS: Adjusted ORs for the highest versus lowest quartiles of exposure were 2.12 (95% CI: 1.07, 4.21; Ptrend = 0.044), 1.84 (95% CI: 1.02, 3.34; Ptrend = 0.018) for the association between urinary mandelic acid, and strontium quartiles with low testosterone concentrations in adult men, respectively. However, no association was observed for the remaining chemicals with testosterone. CONCLUSIONS: The National Health and Nutrition Examination Survey data suggest that elevations in urinary mandelic acid, and strontium levels are negatively related to low serum testosterone levels in adult men.

[Determination of strontium content in whole blood and urine by icp-ms].

Parameters of strontium determination in the whole blood and urine of children living near ore deposits containing up to 20% strontium sulfate have been determined. The average strontium content in the whole blood of two children groups of 109.52 ± 11.07 mg/L and 131.62 ± 12.95 mg/L, significantly exceeded the level in the comparison group 44.2 ± 4.24 mg/L. The average strontium contents of two groups of children in urine were 1252.3 ± 332.2 mg/L and 1341.5 ± 241.8 mg/L, these values were 4.2 and 4.5 times higher than in the comparison group 296.4 ± 61.5 mg/L. The conditions for blood and urine sample preparation were optimized to reduce measure errors and to determine strontium at the reference concentration level. The accuracy of the results has been confirmed by analysis of the standard samples Seronorm™ Whole Blood L1, L2, L3 and Seronorm™ Urine.

Lactose does not enhance calcium bioavailability in lactose-tolerant, healthy adults.

BACKGROUND: There is evidence from animal studies that lactose has a beneficial effect on intestinal calcium absorption. However, data concerning the effect of lactose on calcium absorption in lactose-tolerant adults are inconclusive. OBJECTIVE: Our objective was to investigate the effect of lactose on calcium bioavailability in humans by the use of a stable-strontium test under controlled metabolic conditions. DESIGN: Eleven healthy, lactose-tolerant subjects (8 women, 3 men) randomly received a bolus of 2.27 mmol strontium alone (load A), the bolus with 35 g lactose (load B), or the bolus with 17.5 g glucose and 17.5 g galactose (load C). Blood samples were drawn at 0, 15, 30, 60, 90, 180, 240, and 300 min. Urine specimens were collected during the time intervals -2 to 0, 0-2, 2-4, 4-6, and 6-24 h. RESULTS: Pharmacokinetic parameters of strontium bioavailability were comparable for all 3 loads. In detail, fractional absorption at 240 min for loads A, B, and C was 12.1 +/- 0.7%, 13.0 +/- 1.1%, and 12.2 +/- 0.7%, respectively. Areas under the curve for 0-240 min were 70.8 +/- 6.3, 69.6 +/- 3.5, and 65.8 +/- 5.1 micromol*h/L for loads A, B, and C, respectively (NS). Moreover, fractional strontium excretion values of 5.1 +/- 0.8% (load A), 5.8 +/- 0.4% (load B), and 5.2 +/- 0.8% (load C) were not significantly different. CONCLUSIONS: Lactose does not have a beneficial effect on calcium bioavailability in lactose-tolerant adults.

Measurement of bone resorption by strontium excretion in prelabelled rats.

The body handles strontium (Sr) in a similar way to calcium (Ca) in that Sr is absorbed by the gut, concentrated in bone and excreted in urine and feces. In this study, rats were labelled with Sr during growth and later subjected to various treatments affecting bone resorption and Sr excretion was measured during and after treatment. Six weeks old Wistar rats were repeatedly s.c. injected with SrCl2. After a period of 2 weeks after the last Sr injection the rats were subjected to various treatments. Sr clearance was then measured weekly for 2 weeks. In the first experiment, the Sr labelled rats were sham-operated (sham) or ovariectomized (ovx) and urine collected afterwards. Sham rats were either treated with 4 daily s.c. clodronat injections at the beginning of the urine sampling, fed a low Ca diet (0.08% Ca) during the second sampling week or injected with saline. Urinary Sr excretion was decreased in the clodronate group during the first sampling week and increased in the Ca depleted group during feeding the low Ca diet. Sr excretion by ovx rats was similar to the sham control. In the second experiment, the effect of high-dose treatment with 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) or clodronate on bone resorption induced by Ca depletion was assessed by Sr output in urine and feces. Sr labelled rats were fed a low Ca diet and daily injected with 24,25(OH)2D3 or clodronate for 14 consecutive days. Clodronate significantly decreased Sr output during both sampling weeks. Treatment with 24,25(OH)2D3 resulted in an increased Sr output indicating an increase in bone resorption.

The measurement of radioactivity in people living near the Dounreay Nuclear Establishment, caithness, scotland.

In 1986, a statistically significant excess of leukaemia was reported in young people living near the Dounreay Nuclear Establishment in northern Scotland. The committee on Medical Aspects of Radiation in the Environment (COMARF) confirmed this finding and concluded that, based on conventional dose and risk estimates, the radioactive discharges from the plant could not be held responsible. However, COMARF, recognizing the uncertainties involved in the dose and risk calculations, recommended that levels of radioactivity should be measured in the general population living near the plant. Alpha-emitting contamination has been measured by urinary 239Pu analysis and 241Am in-vivo skull measurements in 66 subjects associated with the Dounreay area and in 42 subjects living remote from reprocessing plants. Whole-body counting was employed to check for gamma ray-emitting contamination. Urinary 90Sr and chromosome abnormality analyses were also carried out on subsets of the study group. No significant inter-group differences for measurements of contamination were demonstrated for groups of leukaemia cases, siblings, parents, matched local controls and controls living remote from reprocessing plants. The findings suggest that it is unlikely that the observed increased incidence in leukaemia is due to the single factor of personal radioactive contamination from the Dounreay Nuclear Establishment.

Re-evaluation of the "week-end effect" data: possible role of urinary copper and phosphorus in the pathogenesis of renal calculi.

Early morning urinary concentrations of 10 elements which had demonstrated a "week-end effect" in a previous study, were subjected to a normalization procedure thereby allowing a re-assessment of their potential role in urolithiasis. After transformation of each concentration to a weighted proportion of the total concentration on each day, only Cu and P values were significantly different for kidney stone formers and healthy controls on all three days indicating that these elements may play a role in the pathogenesis of renal calculi. The results obtained in this study demonstrate that a more meaningful picture of the possible differences in the urinary concentrations of stone formers and normal controls might emerge if "proportional" rather than "raw" concentrations are compared.

Calcium and strontium metabolic studies in patients on CAPD.

BACKGROUND: Strontium is known to affect calcium metabolism both experimentally and in clinical studies on conditions other than end-stage renal failure (ESRF) and continuous ambulatory peritoneal dialysis (CAPD). OBJECTIVE: To investigate Sr metabolism in relation to that of Ca in ESRF patients undergoing CAPD, and the possible influence of the duration of treatment. DESIGN: Cross-sectional observational study. SETTING: University medical center and Institute of Nuclear Physics. PATIENTS: Twenty-four patients on CAPD; 14 chronic renal failure (CRF) patients not on dialysis, and 52 healthy controls. MEASUREMENTS: Calcium and Sr content of serum, urine or dialysate effluent, and selected dietary products. RESULTS: Calcium and Sr are absorbed by the intestinal tract of healthy subjects with equal efficiency. Serum Ca levels were considerably lower in CRF patients than in healthy subjects and patients on CAPD (p < 0.001). Serum Sr was significantly higher in both CAPD and CRF patients than in healthy controls (p < 0.001). The Sr/Ca ratio in the sera of the healthy subjects was defined by the preferential excretion of Sr over Ca by the kidney. This preferential excretion was lost during renal failure. During treatment there was a tendency for the uptake of both Ca and Sr to increase. CONCLUSIONS: Strontium is accumulated in the body during renal failure and CAPD cannot restore normal levels. Considering the varying effects of different doses of Sr on bone metabolism experimentally, it would be interesting to determine by further studies the possible significance of the observed Sr accumulation for renal bone disease.

Radiotoxicological intercomparisons organised by the Commissariat à l'Energie Atomique group in France.

People working in French nuclear plants are monitored either by whole body counting or by the measurement of biological samples. The radiochemical and radiometric procedures used have to be periodically reviewed. A working group, including practising biologists from CEA, EDF and the Armed Forces Health Service, instituted comparisons of radiotoxicological test assessments. Since 1978, about 60 intercomparisons have been made. Currently 30 European laboratories are involved in these intercomparisons. This paper provides a brief history of the intercomparison exercises, describes the logistics of sample collection and preparation, and presents the results, showing the position of each laboratory in relation to the reference and median values. Diagrams produced by radiochemical analysis, relating to plutonium in urine and in faecal samples, and to tritium, strontium and enriched uranium in urine, are analysed.

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.

Age-related changes in strontium to calcium ratios in rat tissues.

The Sr/Ca ratios in plasma, urine, bone, and soft tissues for various ages after weaning in male and female rats were determined to examine the effects of aging on the discrimination between strontium (Sr) and calcium (Ca) under physiological conditions. Age-related changes in the Sr/Ca ratios were similar in all tissues; the Sr/Ca ratios decreased rapidly until about 25-wk-old and then slowly, from that period on, reaching much lower values than in the diet. When the logarithm of the Sr/Ca ratio in each tissue was plotted against the logarithm of age, a linear relationship was observed with statistically significant (p less than 0.05) regression lines. The higher levels of Sr/Ca ratios in all tissues of the younger rats could be explained by the high efficiency of Sr absorption by the small intestine early in life. Parameters for the equations between age and Sr/Ca ratio differed with tissues, suggesting the existence of specific discrimination mechanisms in each tissue.

Metabolism of Ca and Sr in late adult life.

Data are presented on the metabolism of Ca and Sr in a healthy male volunteer who, in a series of investigations conducted between the ages of 53 and 82 y, received controlled intakes of 45Ca, 47Ca, or 85Sr. No age-related trends were established, either in factors affecting the skeletal deposition of the tracers or in their subsequent retention studied for up to 462 d after intake. The data thus lend support to an important working postulate in the ICRP's model of alkaline earth metabolism.