The effect of variation in calcium intake on the growth of wood mice and bank voles

Summary Calcium intake by wild rodents varies with season and habitat. This may have important ecological consequences; several studies have suggested that calcium availability may limit growth and reproduction. We studied the effect on growth of varying the calcium intake of captive wood mice Apodemus sylvaticus (L.) and bank voles Clethrionomys glareolus (Schreber 1780). To determine whether effects observed in the laboratory could be detected in free-living animals, we also compared the body weights and lengths of free-living animals on calcium-poor gritstone areas with those of rodents on calcium-rich limestone habitats where the dietary calcium concentration was between 2 and 5 times higher. Captive wood mice fed high calcium (0.87%) diet grew at the same rate as mice fed low calcium (0.30%) diet but continued growing for longer, thereby achieving higher asymptotic weights. In contrast, captive bank voles fed the high calcium diet grew more slowly and had lower asymptotic weights than voles fed the low calcium diet. As expected from the laboratory growth study, the higher calcium intake of free-living wood mice on the limestone was associated with greater body size compared with mice on the gritstone. However, bank voles were also larger on the limestone, even though high calcium intake impaired growth in captive animals. The contrast between wood mice and bank voles in the effects of calcium on growth, the reason why impaired growth may not be apparent in bank voles from calcium-rich habitats and the ecological significance of these results are discussed.     

The effect of varying calcium intake on calcium metabolism in wild rodent species

Calcium is essential for mammals but distributed heterogeneously in the environment and so the calcium content of the diet of wild small mammals can vary with habitat geology. The effect of varying the calcium intake of two wild rodent species, the granivorous wood mouse Apodemus sylvaticus and the herbivorous bank vole Clethrionomys glareolus , was investigated. Wood mice were similar to laboratory rodents in their calcium metabolism. Net calcium gut absorption efficiency was 11–15% in wood mice fed either high (0˙87%) or low (0˙30%) calcium diet. No more than the equivalent of 6% of the ingested calcium load was excreted in urine but this was sufficient to eliminate the equivalent of all the extra calcium absorbed across the gut when mice were fed the high calcium diet. In contrast, mean net calcium gut absorption efficiency in bank voles was high and increased from 28% to 42% when dietary calcium content was tripled. Urine was important for excreting calcium, the equivalent of up to 23% of intake being eliminated by this route. Despite this, bank voles fed the high calcium diet assimilated three times more calcium than voles fed the low calcium diet; this was in direct proportion to the three-fold difference in dietary calcium concentration. Possible implications for wild rodents in calcium-rich and calcium-poor habitats are discussed.     

Effect of increased dietary calcium on body weight, food and water intake in oral contraceptive treated female rats

The effects of high calcium diet on body weight in OC treated rats are unknown. This study therefore investigated the effect of increasing dietary calcium from 0.9% to 2.5% on body weight, food ingestion, water intake, heart weight index and renal weight index in female Sprague-Dawley rats treated with a combination of OC steroids (ethinyloestradiol + norgestrel). The rats were assigned into three groups of average of 11 rats each; control, OC-treated and OC + Calcium – treated groups and administered orally for 10 weeks. Food and water intake, body weight, cardiac weight index, left ventricular weight index, renal weight index and serum calcium level were determined. The result shows that OC treated rats had significantly lower serum calcium concentration, body weight gain, food, water and calcium intake than those of the control rats. The OC + Calcium – treated rat had significantly higher serum calcium concentration, food, water and calcium intake but significantly lower body weight than those of the OC - treated rats. OC + Calcium - treated rats had significantly higher water intake, calcium intake and significantly lower body weight and food intake when compared with the control rats. Cardiac weight index and renal weight index was comparable in all groups. In conclusion, combined OC-induced reduction in weight gain might be associated with inhibition of the feeding center and consequent inhibition of the thirst center. Co-administration of dietary calcium augmented the reduction in weight gain seen in OC-treated rats probably by further suppression of the feeding and thirst centers.     

Effects of calcium deprivation and orchidectomy on bone composition in the rat.

The effects of calcium deprivation and of orchidectomy, separately and combined, on body growth and bone composition have been examined in mature male rats. Calcium deprivation had no significant effect on the rate of body growth but femoral bone weight, bone ash weight and total calcium and phosphorus contents of the femora were reduced while the water content increased. However, there were no significant changes in the ratio of bone weight to body weight, in the amounts of calcium or phosphorus per unit weight of bone, or in the ratio of calcium to phosphorus in the bone. Orchidectomy reduced the rate of body growth, the mean weight of the femora and the ratio of bone weight to body weight. There was a 60% decrease in bone water and a 30--35% reduction in the calcium and phosphorus content of the femora but the amounts of ash, calcium and phosphorus per unit weight of bone fell by only 6--10%. The combination of orchidectomy and calcium deprivation had no greater effect on body weight, bone weight or bone composition than had orchidectomy alone. It is concluded that calcium deprivation and orchidectomy both cause osteoporosis in mature rats but the effects of orchidectomy are more severe than those of calcium deprivation and there appears to be some demineralization of the bone remaining after orchidectomy.     

Characterization of calcium accumulation in the brain of rats administered orally calcium: The significance of energy-dependent mechanism

The characterization of calcium accumulation in the brain of rats administered orally calcium chloride solution was investigated. Rats received a single oral administration of calcium (15–50 mg/100 g body weight), and they were sacrificed by bleeding-between 15 and 120 min after the administration. The administration of calcium (50 mg/100 g) produced a significant increase in serum calcium concentration and a corresponding elevation of brain calcium content, indicating that the transport of calcium into the brain is associated with the elevation of serum calcium levels. The increase in brain calcium content by calcium administration was not appreciably altered by the pretreatment with Ca²⁺ channel blockers (verapamil or diltiazem with the doses of 1.5 and 3.0 mg/100 g). In thyroparathyroidectomized rats, the administration of calcium (50 mg/100 g) caused a significant increase in brain calcium content, indicating that calcium-regulating hormones do not participate in the brain calcium transport. Now, brain calcium content was clearly elevated by fasting (overnight), although serum calcium level was not significantly altered. Calcium administration to fasted rats induced a further elevation of brain calcium content as compared with that of control (fasted) rats. The fasting-induced increase in brain calcium content was appreciably restored by refeeding. This restoration was also seen by the oral administration of glucose (0.4 g/100 g) to fasted rats. The present study demonstrates that serum calcium is transported to brain, and that the increased brain calcium is released promptly. The release of calcium from brain may be involved in energy metabolism, and this release may be weakened by the reduction of glucose supply into brain. The finding suggests a physiological significance of energy-dependent mechanism in the regulation of brain calcium.     

Studies on the synthesis and anti-Osteoporosis of estrogen-GHRPs linkers

The linkers of estrogen-GHRPs were prepared by the combination of estradiol, estrone, TyrGlyGlyPheLeuOH, and TyrGlyGlyPheLeuOH. Their anti-osteoporosis effect was evaluated by analyzing the data, for instance the weight of the body, femur, femur ash, the content of calcium and phosphor in the femur, the content of calcium and ALP activity in the serum, obtained from the corresponding bioassay in vivo. The results indicated that the anti-osteoporosis potency for estradiol, estrone, TyrGlyGlyPheLeuOH and TyrGlyGlyPheLeuNH(2) may be totally enhanced each other via the corresponding linkers.     

Seasonal regulations of energetics, serum concentrations of leptin, and uncoupling protein 1 content of brown adipose tissue in root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau

Survival of small mammals in winter requires proper adjustments in physiology, behavior and morphology. The present study was designed to examine the changes in serum leptin concentration and the molecular basis of thermogenesis in seasonally acclimatized root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau. In January root voles had lower body mass and body fat mass coupled with higher nonshivering thermogenesis (NST) capacity. Consistently, cytochrome c oxidase activity and mitochondrial uncoupling protein-1 (UCP1) protein contents in brown adipose tissues were higher in January as compared to that in July. Circulating level of serum leptin was significantly lower in winter and higher in July. Correlation analysis showed that serum leptin levels were positively related with body mass and body fat mass while negatively correlated with UCP1 protein contents. Together, these data provided further evidence for our previous findings that root voles from the Qinghai-Tibetan plateau mainly depend on higher NST coupled with lower body mass to enhance winter survival. Further, fat deposition was significantly mobilized in cold winter and leptin was potentially involved in the regulation of body mass and thermogenesis in root voles. Serum leptin might act as a starvation signal in winter and satiety signal in summer.     

Seasonal Changes of Body Iron Status Determine Cadmium Accumulation in the Wild Bank Voles

The objective of this study was to examine relations between body iron (Fe) status and cadmium (Cd) accumulation in a small rodent, the bank vole, caught from the wild population in late autumn (November) and early spring (March). The concentrations of Fe in the liver, kidneys, and duodenum in the bank voles from the spring were only 30%, 60%, and 70%, respectively, of those found in the animals from the autumn. An analysis of hematocrit and hemoglobin content of blood showed no significant effect of the season, suggesting that the animals from the spring were not anemic. The exposure to dietary Cd (10 μg/g) for 7 days resulted in 70% higher accumulation of Cd in the liver and kidneys of the spring than autumn bank voles, and the concentration of Cd in the duodenum was 3.5 times higher in the spring animals, despite the fact that relative Cd intake was significantly higher in the autumn bank voles. The data indicate that seasonal changes of body Fe status occurring in the wild bank voles may influence tissue accumulation of Cd.     

Effect of synthetic oligopeptides on osteoporosis

The objective of this study was to establish the solution method of GHRPS, the synthetic oligopeptides Tyr-Gly-Gly-Phe-Met-NH2, Tyr-Gly-Gly-Phe-Met-OH, Tyr-Gly-Gly-Phe-Leu-NH2, Tyr-Gly-Gly-Phe-Leu-OH, Tyr-Gly-Gly-Phe-Gly-NH2, and Tyr-Gly-Gly-Phe-Gly-OH, to verify their effect on osteoporosis. Male ICR mice (20 +/- 2 g) were used. The intramuscular injection dose of 6.3 mg/kg prednisone induced a significant decrease of body and femur weight of the animals. The subcutaneous injection dose of 18 microg/kg synthetic peptide was not effective to prevent the decrease of body and femur weight of the animals. The subcutaneous injection dose of 6.3 mg/kg prednisone elicited a decrease in content of femur calcium and in the level of serum calcium of the animals. The subcutaneous injection dose of 18 microg/kg Tyr-Gly-Gly-Phe-Leu-NH2, or Tyr-Gly-Gly-Phe-Leu-OH, or Tyr-Gly-Gly-Phe-Gly-NH2, significantly increased the content of femur calcium and decreased the level of serum calcium of the animals. It was also observed that the subcutaneous injection dose of 18 microg/kg Tyr-Gly-Gly-Phe-Gly-OH, Tyr-Gly-Gly-Phe-Leu-OH, Tyr-Gly-Gly-Phe-Met-OH, Tyr-Gly-Gly-Phe-Met-NH2 significantly increased the content of femur phosphorous and decreased the activity of ALP of the animals.     

Effect of synthetic oligopeptides on osteoporosis

The objective of this study was to establish the solution method of GHRPS, the synthetic oligopeptides Tyr-Gly-Gly-Phe-Met-NH2, Tyr-Gly-Gly-Phe-Met-OH, Tyr-Gly-Gly-Phe-Leu-NH2, Tyr-Gly-Gly-Phe-Leu-OH, Tyr-Gly-Gly-Phe-Gly-NH2, and Tyr-Gly-Gly-Phe-Gly-OH, to verify their effect on osteoporosis. Male ICR mice (20+/-2 g) were used. The intramuscular injection dose of 6.3 mg/kg prednisone induced a significant decrease of body and femur weight of the animals. The subcutaneous injection dose of 18 microg/kg synthetic peptide was not effective to prevent the decrease of body and femur weight of the animals. The subcutaneous injection dose of 6.3 mg/kg prednisone elicited a decrease in content of femur calcium and in the level of serum calcium of the animals. The subcutaneous injection dose of 18 microg/kg Tyr-Gly-Gly-Phe-Leu-NH2, or Tyr-Gly-Gly-Phe-Leu-OH, or Tyr-Gly-Gly-Phe-Gly-NH2 significantly increased the content of femur calcium and decreased the level of serum calcium of the animals. It was also observed that the subcutaneous injection dose of 18 microg/kg Tyr-Gly-Gly-Phe-Gly-OH, Tyr-Gly-Gly-Phe-Leu-OH, Tyr-Gly-Gly-Phe-Met-OH, Tyr-Gly-Gly-Phe-Met-NH2 significantly increased the content of femur phosphorous and decreased the activity of ALP of the animals.     

The effect of heavy metal accumulation on metallothionein content in selected tissues of bank voles and yellow-necked mice caught near a steelworks and zinc smelter

The effect of cadmium, zinc, and copper accumulation on metallothionein content in the selected tissues of bank voles and yellow-necked mice trapped near the Sendzimir Steelworks in Krakow and the zinc smelter in Bukowno were analysed. The Borecka Forest was chosen as a control area. The highest cadmium concentration, 32.98 microg g(-1) dry weight, was detected in the kidneys of the bank voles caught in the Bukowno area. Zinc and copper concentrations in the tissues did not exceed the critical values. Metallothionein content in the liver and kidneys was associated with heavy metal accumulation in the tissues. The highest content of sulphydryl groups was detected in the livers of the bank voles trapped within the neighbourhood of the zinc smelter in Bukowno. The highest level of disulphide bonds was found in the kidneys of the bank voles from the same area.     

The effect of verapamil on mitochondrial calcium content in normoxic, hypoxic and reoxygenated rat liver

Calcium channel blockers protect cells against ischaemia-reperfusion injury. In the present study, the effect of verapamil on mitochondrial calcium content was investigated in situ in normoxic, hypoxic and reoxygenated rat liver. Subcellular distribution of exchangeable calcium ions, which form an electron-dense precipitate with antimonate, was demonstrated with the glutaraldehyde-osmium antimonate technique. Calcium precipitates were quantified morphometrically using automatic image analysis. In normoxic liver, the mitochondrial calcium content formed a gradient decreasing from the periportal to perivenous regions. The low mitochondrial calcium content in perivenous regions remained unaffected in all experimental conditions. In hypoxic and reoxygenated liver, the calcium content in mitochondria of the periportal areas was significantly reduced. Verapamil pretreatment levelled the calcium gradient in normoxic liver by reducing the periportal calcium content. Verapamil had no effect on the mitochondrial calcium content in hypoxic liver. In contrast, in verapamil-pretreated reoxygenated liver, the mitochondrial calcium content in periportal mitochondria increased significantly, thus restoring the zonal calcium gradient. In conclusion, these data suggest that modulations of mitochondrial calcium content in the periportal region of the liver lobule may play an important role in the protective effects of verapamil against ischaemia-reperfusion injury     

No effect of dietary calcium on body weight of lean and obese mice and rats

Recent epidemiological and animal studies have led to the hypothesis that low dietary calcium intakes contribute to obesity. Here, we evaluated whether calcium influenced the body weight of normal-weight and obese rodents. All experiments involved female C57BL/6J mice or Sprague-Dawley rats fed normal- or high-energy-density diets (3.8 o 4.7 kcal/g). Calcium intake was manipulated by allowing mice to drink sweetened 30 mM CaCl(2) solution or feeding mice and rats diets differing in calcium content (0.2%, 0.6%, o 1.8% Ca(2+)). Blood samples were taken from rats to confirm that the diets had their intended effects on metabolism. There were no effects of the calcium manipulations on energy intake, body weight, or carcass fat content and no simple elation between calciotropic hormones and body weight. One experiment found a significant decrease in body weight gain of lean and obese rats fed the 1.8% Ca(2+) diet, but we suspect that this was due to forced consumption of the unpalatable diet, reducing growth. These studies provide little support for the hypothesis that dietary calcium contributes to the etiology or maintenance of obesity.     

Recognition of interspecific familiar versus unfamiliar odours among bank voles and yellow-necked mice

Two experiments (laboratory and field-laboratory) were designed to determine whether individual bank volesClethrionomys glareolus (Schreber, 1780) and yellow--necked miceApodemus flavicollis (Melchior, 1834) could distinguish heterospecific odour cues from familiar and unfamiliar individuals. In the laboratory experiment each male bank vole was familiarized for 24 h with odour (cotton wool impregnated with urine and faeces) of male yellow-necked mice and yellow-necked mice were familiarized with odour of male bank voles. In the field-laboratory experiment the individual bank voles and yellow-necked mice captured at the same point were considered familiar and transfered to the laboratory. In laboratory, these individuals were tested in a box (for 5 h) affording them the choice between the odours of familiar and unfamiliar heterospecific males. Bank voles discriminated between familiar and unfamiliar yellow--necked mouse odours. Male yellow-necked mice seemed to have a similar ability to recognise odours of familiar bank voles. It is proposed that interactions between these two species occur not only on the species level, but also on the level of individual. This phenomenon (probably asymmetric) can play an important role in spatial orientation, and influence direct contacts between individuals of these species.     

Reproductive investment under fluctuating predation risk: Microtine rodents and small mustelids

Summary We studied the reproductive investment of microtine rodents (bank vole (Clethrionomys glareolus),Microtus epiroticus andMicrotus agrestis) in western Finland under predation risk from small mustelids. During 1984–1992, the yearly mean litter size of overwintered bank voles was smaller at high least weasel and stoat densities than at low densities (close to 3 versus 4–5). In addition, the annual mean litter size of young bank voles was negatively correlated to the least weasel density. In youngM. agrestis voles, the yearly late summer litter size was negatively associated with the autumn density of small mustelids. In the crash phase of the vole cycle (1989 and 1992), we removed small mustelids (mainly least weasels) from four unfenced areas in late April to late May and studied the reproduction of voles in four removal and comparable control areas (each 2–4 km²). Reduction of small mustelids significantly increased the proportion of pregnant bank vole females, but not that of pregnantMicrotus vole females. We conclude that predation risk apparently reduced reproductive investment of free-living bank vole females; these voles appear to trade their current parental investment against future survival and reproductive prospects. Accordingly, the presence of small mustelids (or their scent) may slow down the reproductive rate of voles. As antipredatory behaviours occurred on a large scale, our results add evidence to the hypothesis that crashes in multiannual vole cycles are driven by small mustelid predators.     

Optimized extraction of calcium malate from eggshell treated by PEF and an absorption assessment in vitro

Under optimized pulsed electric field (PEF) treatment for production of eggshell calcium malate (ESCM) by one-factor-at-a-time test and ternary quadratic regression orthogonal combination design (TQROCD), an absorption assessment of ESCM treated by the best conditions of PEF were performed in male mice with apparent calcium absorption rate (ACAR), serum alkalinity phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP), serum calcium and serum phosphorus, length of femurs and skeletal calcium content were studied. The highest dissoluble calcium malate content (7.075 mg/mL) was obtained with the 6.0% malic acid, the electric field intensity of 20 kV/cm, and pulse duration of 24 μs. In vitro, ESCM prepared by the best conditions of PEF at doses of 133.0 mg kg(-1) d(-1) for 70 d not only significantly improve the ALP activity, the femur length and calcium content of bone of the mice (P<0.05) but also decreased the levels of TRAP (P<0.05). The ratio of calcium and phosphorus was in the normal range. PEF could be taken as a highly effective, environmentally friendly and energy-saving method for preparation of ESCM, which treated by PEF could promote the absorption of calcium in vitro, extraordinary can promote bone development and a healthy bone.     

Changes in Calcium Reserves in Breeding Lesser Snow Geese (Chen caerulescens caerulescens)

Calcium and fat reserves of the femur medullary bone were examined in sexually mature lesser snow geese (Chen caerulescens caerulescens) collected during the 1974–1975 season. In females, femur calcium and fat levels increased by 80 and 30%, respectively, during the spring migration, much of the increase taking place while the birds staged in southwestern Manitoba and North Dakota prior to their departure for the breeding area. In males. femur calcium levels showed no seasonal change but femur fat increased in a manner similar to that found in the females, although the increase was not as great (17%). In the females, femur fat content fell by 40% during egg-laying whereas in males a decrease in femur lipid was not evident until incubation was well underway. Femur calcium levels in females declined during egg production and early incubation, showing a 56% decrease over spring migratory levels, indicating that dietary calcium intake was limited during the nesting period. However, the low femur calcium levels in birds collected during the spring were not significantly different from those of wintering birds, suggesting that no calcium deficiencies were apparent. Plasma calcium levels in males remained relatively constant throughout the year, although there was some elevation in May. Plasma calcium levels in the females increased almost threefold during egg laying and returned to pre-laying levels during incubation. Medullary bone was evident only in reproducing females and appeared during spring migration, concomitant with increased femur weight, fat and calcium content. Medullary bone degradation commenced during the first week of incubation and no medullary bone was in evidence by molt. Calcium reserves of medullary bone accounted for only 17.2% of the calcium required for eggshell production, suggesting that. at least during the laying period, the female must depend on some exogenous source, perhaps from grit or brackish water.     

Effect of dietary calcium on cadmium absorption and retention in suckling rats

The effect of calcium supplementation on absorption and retention of cadmium in the suckling period was evaluated in Wistar rat pups of both sexes. Animals were maintained in the litters with the mother rats and supplemented with 1%, 3% or 6% calcium (as CaHPO₄×2H₂O) in cow's milk by artificial feeding from day of birth 6 through 14. All rats were exposed to cadmium (as CdCl₂×H₂O) either orally or parenterally. Oral cadmium dose of 0.5 mg/kg body weight a day was administered through nine-day period of calcium supplementation and parenteral cadmium dose was injected subcutaneously in a single dose of 0.5 mg Cd/kg body weight prior to calcium supplementation. On experimental day 10 (at the age of pups of 15 days) all animals were killed and the liver, kidneys, brain and carcass (body without organs and skin) were removed for element analyses. Cadmium and essential elements calcium, zinc and iron were analysed in the tissues by atomic absorption spectrometry. Results showed that after oral exposure cadmium concentrations in all calcium-supplemented groups were significantly decreased in the organs and carcass and that the effect was dose-related. No such effect of calcium was found after parenteral cadmium exposure. Calcium supplementation per se significantly increased calcium concentration in the carcass and had no effect on iron in organs and zinc in carcass. It was concluded that calcium supplementation during the suckling period could be an efficient way of reducing oral cadmium absorption and retention without affecting tissue essential trace element concentrations.     

Relationship of serum and saliva calcium, phosphorus and alkaline phosphatase with dry mouth feeling in menopause

doi: 10.1111/j.1741‐2358.2012.00619.x Relationship of serum and saliva calcium, phosphorus and alkaline phosphatase with dry mouth feeling in menopause Objectives: The aim of this study was to compare serum and saliva calcium, phosphorus and alkaline phosphatase of menopausal women with/without dry mouth (DM) feeling. Background: The composition of saliva in menopause women with/without DM feeling is different. Some of these differences are in hormones that are related to bone turnover. Methods: A case–control study was carried out on 60 selected menopausal women aged 45–79 years with or without DM feeling (30 as case, 30 as control), conducted at the Clinic of Oral Medicine, Tehran University of Medical Sciences. The phosphorus concentration was measured by photometrical measurement of the blue colour formed after the addition of ammonium molybdate and stannous chloride; calcium was measured by Arsenazo reaction; and alkaline phosphatase by the pNPP‐AMP method. Statistical analysis of Student’s t‐test was used. Results: The mean serum phosphorus and alkaline phosphatase, stimulated and unstimulated saliva calcium and alkaline phosphatase levels were significantly higher in the menopausal women suffering from DM. There were no significant differences between groups regarding saliva phosphorus and serum calcium concentration. Conclusion: Calcium, phosphorus and alkaline phosphatase appear associated with DM feeling in menopause.     

Interactive effects of habitual physical activity and calcium intake on bone density in boys and girls.

The purpose of this study was to assess the interactive effects of habitual physical activity (total and vigorous intensity) and calcium intake on bone mineral content (BMC) in prepubertal boys and girls. Seventy-six children, aged 8-11 yr, wore accelerometers for up to 7 days to assess activity. Calcium intake was estimated by a 4-day weighted food diary. BMC and areal density (bone mineral density) were measured at the total body, proximal femur, and femoral neck by using dual-energy X-ray absorptiometry. Moderated regression analyses were used to assess the contributions of physical activity (total and vigorous) and calcium intake to BMC, residualized for bone area and body mass. Interactive effects of vigorous activity (> or =6 metabolic equivalents) and calcium intake were found at the total body in boys (b = 2.90 x 10(-3)) and in girls (b = 6.58 x 10(-3)) and at the proximal femur (b = 9.87 x 10(-5)) and femoral neck (b = 2.29 x 10(-5); where b is the regression coefficient from final equation) in boys only; residualized BMC was high only if both vigorous activity and calcium intake were high. There were no interactive effects of total activity and calcium intake. This study provides evidence for synergistic action of habitual vigorous activity and calcium intake on bone mass in children. Recommendations for optimizing bone mass should reflect this synergism.