Caffeine does not causein vitro calcium loss from neonatal mouse calvaria

Summary Calcium concentration of media containing calvaria from 6-day-old mice were unchanged by four doses of caffeine in a 48-hourin vitro system. The caffeine-treated calvaria were similar morphologically at all levels when compared to their littermate controls. In the culture conditions used, caffeine does not stimulate bone to release calcium.     

Urinary calcium excretion in healthy children and adolescents

Urinary calcium (Ca) excretion was determined in 1,578 24-h urine samples from 507 healthy children and adolescents (252 boys, 255 girls; 2.8–18.4 years) participating in the DONALD Study and is presented for 32 different age and sex groups. Calciuria values related to body weight (mg/kg per day) were relatively constant except for a transient decrease during puberty in all centiles, with a later onset in boys than girls. Distribution of calciuria (mg/kg per day) was best normalized by log transformation, with an almost constant standard deviation of the log-transformed values. Ca excretion was ≥4 mg/kg per day in 8.6% and ≥6 mg/kg per day in 1.5% of the urine samples. Based on Ca excretion rates of 1,080 pairs of 24-h urine samples from 364 children and adolescents, sensitivity, specificity, and the predictive value for hypercalciuria (≥4 mg/kg per day) in the next urine sample were calculated at three test levels classifying calciuria of the initial urine sample. In summary, this study presents normal values of urinary Ca excretion related to age and sex in a population of healthy German children and adolescents consuming a typical western-style diet. A high level of calciuria in a random urine sample is important in the diagnosis of hypercalciuria. Received: 25 February 1997 / Revised: 28 April 1999 / Accepted: 3 May 1999     

Effects of a cation exchange resin on intestinal calcium absorption and urinary calcium in calcium stone formers

Summary The effect on the urinary excretion of calcium of an oral cation exchange resin with-out phosphorus was studied in healthy control subjects and patients with recurrent calcium lithiasis under out-patient conditions. An immediate reduction of intestinal calcium absorption and urinary calcium excretion was found in five control subjects and in one patient after ingestion of resin, whereas calcium excretion remained unchanged in all other patients during long-term treatment. In addition, signs of mild transitory hyperparathyroidism together with an increase in intestinal calcium transport were observed during treatment. It is suggested that intraluminal binding of calcium ions to the resin leads to substantial changes in calcium metabolism with the result that urinary calcium excretion returns to pretreatment values.     

Intestinal calcium absorption from different calcium preparations: Influence of anion and solubility

Not only is the calcium content of a preparation significant for providing adequate calcium supplementation for the prophylaxis and therapy of osteoporosis, but also its bioavailablity is of essential importance. In the present study, the bioavailability of calcium citrate and calcium lactogluconate/carbonate from a therapeutic dose (= 500 mg Ca²⁺) was compared in men aged between 45 and 60 years on an intra-individual basis. Calcium citrate was administered both as a solution and as a suspension to 18 healthy volunteers. Using a double-isotope method, the intestinal absorption from the three preparations was determined in randomized order at intervals of 2–4 weeks. The stable isotope⁴⁴Ca (20 mg), in highly enriched form, was added in each case to the ready-to-drink solutions and, at the same time, a sterile and pyrogen-free solution containing 5 mg of the stable isotope⁴²Ca was injected intravenously. The intestinal calcium absorption was then determined after 24 h on the basis of the ratio of the two isotopes in the plasma. There was a significantly higher absorption of 29% from the citrate solution than from the lactogluconate/carbonate solution (25%). Absorption from the citrate suspension was similar to that from the lactogluconate/carbonate solution. While no correlation was found between the measured values for calcium absorption from the three preparations and the plasma concentration of 1,25-dihydroxycholecalciferol, significant inverse correlations with the basal parathyroid hormone concentration were observed for the citrate and lactogluconate/carbonate solution. The results of this study show that quantitative data on intestinal calcium absorption can be obtained without employing radioactive isotopes in humans. Moreover, they show that calcium absorption is not determined only by the solubility and the degree of ionization of the calcium salt administered, but rather that it is of a complex nature.     

正常钙摄入老年男性骨质疏松与钙调节激素相关性的调查与分析

目的：了解正常钙饮食和接受充足阳光照射老年男性骨质疏松的发病情况,对这组老年男性骨质疏松和钙调节激素间的相关性进行调查与分析。方法：95例正常钙饮食和充足光照的老年男性,测定骨密度后,分骨质疏松组和非骨质疏松组,检测钙调节相关激素。用统计学方法对两组进行比较。结果：正常钙饮食和充足光照的老年男性随年龄增加出现骨质疏松,钙调节激素特点为骨质疏松组较非常骨质疏松组,hCT和IGF－1降低,BGP增高,TE2,TTT,hPTH,25-OH-VD无差异。结论：正常钙饮食可抑制骨质疏松组继发的hPTH升高,充足光照可避免25－OH－VD减低,但不可避免地发生hCT,IGF-1,TTT,TE2随年龄增加而降低,故老年男性骨质疏松的发病可能与年龄增加相关激素（TE2,TTT,hCT,IGF-1)的变化密切相关。     

Comparison between the fractional isotopic calcium absorption and an oral calcium tolerance test

Summary In 27 subjects with several disorders of calcium metabolism, the fractional intestinal absorption of⁴⁷CaCl₂ was rather poorly correlated with the urinary output of calcium or with the maximal increase of serum calcium after an oral calcium load. Conversely, a good correlation was observed with the product of these parameters. We propose that this product be used as an estimate of intestinal calcium absorption when a radioisotopic method is not available.     

一水草酸钙与二水草酸钙结石形成机理的研究

目的　探讨一水草酸钙（ＣＯＭ） 与二水草酸钙（ＣＯＤ） 结石形成的机制。　方法　应用红外光谱仪对２５８ 块尿结石成分进行检测,同时检测３０ 例患者２４ｈ 尿液生化指标,对测定结果利用ＳＰＳＳ软件进行ｔ 检验。　结果　（１） 尿钙：ＣＯＭ 组（４．８３ ±１ ．９８）ｍ ｍｏｌ／２４ｈ,ＣＯＤ 组（９．８８ ±４ ．２８）ｍｍｏｌ／２４ｈ,Ｐ＜ ０ ．０１ ;（２） 尿磷：ＣＯＭ 组（１９ ．４０ ±９．６９）ｍ ｍｏｌ／２４ｈ,ＣＯＤ 组（２９．２０ ±１２．００）ｍ ｍｏｌ／２４ｈ,Ｐ＜ ０．０５,两组尿钙、尿磷差异有显著性。　结论　二水草酸钙结石患者尿钙、尿磷高于一水草酸钙结石患者,表明二水草酸钙的形成与高钙尿及磷酸盐异质成核有关,而一水草酸钙的形成可能与尿中抑制物缺乏有关。     

正常人和草酸钙结石病人尿草酸钙晶体基质

以改良Ｍｏｒｓｅ和Ｒｅｓｎｉｃｋ法提取１０例上尿路草酸钙结石病人和１１例正常人的尿草酸钙晶体基璺，用双向聚丙烯酰胺凝胶电泳对晶体基质及结晶前后大分子物的蛋白质组成进行了比较分析。     

不同钙离子浓度透析液对单次血液透析钙平衡的影响

目的观察三种不同钙离子浓度透析液对维持性血液透析患者单次透析过程中血钙的影响,为透析液钙离子浓度的个体化选择提供理论参考。方法选择2014年1月在哈尔滨医科大学附属第一医院血液净化中心接受维持性血液透析治疗的患者80例为研究对象,随机分为3组,根据使用不同钙离子浓度分别为1.25 mmol/L(DCa 1.25组)、1.5 mmol/L(DCa 1.50组)和1.75 mmol/L(DCa 1.75组)的透析液进行单次血液透析治疗,每次透析4 h,3组所用透析液除钙离子浓度不同外,其他透析液主要成分组间无差别。分别检测每组透析前、后及下一次透析前的血肌酐(SCr)、尿素氮(BUN)、血白蛋白(albumin,Alb)、血钙、血磷等生化指标,同时监测单次透析前后患者的血压变化。结果对患者透析前基线数据初步分析结果表明,透析前iPTH水平为(458.7±408.2)ng/L、血钙(2.2±0.2)mmol/L、血磷(2.1±0.6)mmol/L、钙磷乘积(57.4±18.9)。iPTH、血钙、血磷达标率分别为53.8%、46.3%,25.0%;透析患者普遍伴有低钙血症(占48.8%)、高磷血症(占71.3%)和高甲状旁腺素血症(占23.8%)。单次透析治疗结束后的血钙水平分别为DCa 1.25组(2.27±0.20)mmol/L、DCa 1.50组(2.53±0.21)mmol/L、DCa 1.75组(2.51±0.20)mmol/L,组间比较差异有统计学意义(F=12.52,P0.01)。与透析前相比较,3组透析后血钙浓度较透析前均有所增加;协方差分析结果表明,在扣除透析前血钙浓度的影响因素后,DCa 1.25组血钙平均增加量最小。单次透析结束后血钙达标率分别为65.4%(DCa 1.25组)、48.1%(DCa 1.50组)、58.8%(DCa1.75组);透析结束后高钙血症的发生率DCa 1.75组(占41.2%)与DCa 1.50组(占51.9%)明显高于DCa 1.25组(占19.2%)。三种透析液对透析患者的血磷、血压影响差异均无统计学意义(P0.05)。结论单次使用钙离子浓度为1.25 mmol/L的透析液治疗,对透析后血钙浓度的影响最小、血钙达标率最高、高钙血症的发生率最低;与钙离子浓度分别为1.50 mmol/L和1.75 mmol/L透析液比较,钙离子浓度1.25 mmol/L更接近人体生理离子钙浓度。     

复发性草酸钙结石与尿内酸性粘多糖的关系

为了探讨酸性粘多糖（ＧＡＧｓ）对草酸钙结石形成的抑制作用机理，收集了１２例正常人及１５例复发性草酸钙结石病人２４小时尿，经超滤后，用ＰｒｏｎａｓｅＥ蛋白酶降解尿中糖蛋白，纯化ＧＡＧｓ，并分别测定了蛋白水解前后尿样中ＧＡＧｓ含量及种晶体系下ＧＡＧｓ对草酸钙晶体粒度分布。结果表明：（１）水解前后，正常人尿中ＧＡＧｓ含量均比结石病人高；（２）草酸钙晶体生长抑制指数（Ｉｇ）、聚集抑制指数（Ｉａ）与ＧＡＧｓ的含量成正比。     

Calcium absorption from a new calcium delivery system (CCM)

Absorption of calcium from a highly soluble form of calcium, a mixed calcium citrate-malate^* salt (CCM), was tested against calcium carbonate and milk in both rats and humans. The rat method estimated absorption from the 6-day retention of an oral tracer, and the human method employed the standard double-isotope procedure. CCM was given both as a dry powder and in an organe juice beverage. In two experiments in rats calcium from CCM was absorbed at least as well as, if not better than from calcium carbonate or milk. In two separate experiments in humans, calcium from CCM was absorbed significantly better than from calcium carbonate or milk. We conclude that CCM exhibits excellent bioavailability and that this formulation is a useful addition to the forms of calcium now available either for direct supplementation or for food fortification.     

Absorbability of calcium sources: The limited role of solubility

Summary Fractional absorption of seven chemically defined calcium sources was measured in normal adult women under standardized load conditions. Solubility of the sources in water at neutral pH ranged from a low of 0.04 mM to a high of 1500 mM. The relationship of solubility to absorbability was weak. In the range from 0.1 to 10 mM, within which most calcium supplement sources fall, there was no detectable effect of solubility on absorption. Data from four food sources are presented for comparison. Absorbability of food calcium was not clearly related to absorbability of the dominant chemical form in the food concerned. These findings suggest that (1) even under controlled, chemically defined conditions, solubility of a source has very little influence on its absorbability; and (2) absorbability of calcium from food sources is determined mainly by other food components.     

Acute caffeine effects on urine composition and calcium kidney stone risk in calcium stone formers

PURPOSE: Caffeine increases urinary calcium (ca) excretion in nonstone formers. We designed a study to determine the effect of caffeine consumption on urinary composition in stone formers. MATERIALS AND METHODS: A total of 39 normocalcemic patients with calcium stones consumed caffeine (6 mg/kg lean body mass) after 14 hours of fasting. Urinary composition was compared 2 hours before and 2 hours after caffeine consumption. Control subjects included 9 nonstone formers studied contemporaneously with patients plus data from 39 nonstone formers from previous studies matched to each patient by level of fasting calcium/creatinine (Cr), gender and age. RESULTS: Caffeine increased urinary Ca/Cr, magnesium/Cr, citrate/Cr and sodium/Cr but not oxalate/Cr in stone formers and controls. The Tiselius stone risk index for calcium oxalate precipitation increased from 2.4 to 3.1 in stone formers and from 1.7 to 2.5 in nonstone formers. Of the 39 stone formers 32 had an increased Tiselius risk index after caffeine. Post-caffeine increases in Ca/Cr and Na/Cr were highly correlated. CONCLUSIONS: Caffeine consumption may modestly increase risk of calcium oxalate stone formation.     

Tap water calcium and its relationship to renal calculi and 24h urinary calcium output in Great Britain

Summary Tap water calcium content in Great Britain has been re-determined and found to vary with geological age; the older the land mass the lower is the local tap water calcium content. No obvious correlation was observed between local tap water calcium content and the number of patients discharged from hospital with a first diagnosis of renal calculi. Variations in tap water calcium content were found to account for less than three per cent of the variation observed in 24 h urinary calcium output.     

Urinary excretion of calcium and phosphate in preterm infants

The aims of this study were to determine reference ranges for the urinary calcium (UCa/Cr) and phosphate (UPO(4)/Cr) creatinine ratios and to study factors influencing these ratios in a representative population of preterm infants managed according to current nutritional guidelines. Spot urine samples were obtained from 186 preterm infants (gestation 24-34 weeks) for measurement of UCa/Cr and UPO(4)/Cr ratios as part of a routine metabolic bone screening program, once every 2-4 weeks from the 3rd to the 18th week of life. Data were also collected on gender, appropriate or small for gestational age (SGA), nutrition [total parenteral nutrition (TPN), preterm or term formula, and breast milk], plasma Ca, P0(4), urea, and electrolytes and on the use of drugs (frusemide, dexamethasone, and theophylline). Data from infants treated with any of these three drugs were analyzed separately and not included in establishing the reference ranges for UCa/Cr and UPO(4)/Cr. The mean gestational age of the study population was 28 weeks (range 24-34 weeks). The 95th percentile for UCa/Cr at 3 weeks of age was 3.8 mmol/mmol and decreased significantly with increasing postnatal age (P<0.001). The 95th per-centile for UPO(4)/Cr was 26.69 mmol/mmol at 3 weeks of age, but this did not change significantly with increasing postnatal age (P=0.296). On univariate analysis there was no significant association of UCa/Cr and UPO(4)/Cr with gender and type of enteral nutrition. The UCa/Cr was lower in infants who were SGA (P=0.013) and with low plasma Ca (P=0.008). Infants on TPN had significantly higher UCa/Cr (P =0.019) and lower UPO(4)/Cr ratios(P<0.001). Multivariate analysis confirmed the decrease in UCa/Cr ratio with increasing postnatal age, but the SGA effect was eliminated. The use of furosemide(P<0.001) and theophylline (P=0.003) was associated with a significant increase in the UCa/Cr ratio. The use of dexamethasone was also associated with an increase in UCa/Cr ratio, but this did not achieve statistical significance (P=0.339). The use of furosemide, theophylline,and dexamethasone had no effect on UPO(4)/Cr. We report a reference range for UCa/Cr and UPO(4)/Cr ratios and factors influencing these ratios in a representative population of preterm infants between 24 and 34 weeks gestation, managed according to current nutritional guide-lines.     

Caffeine has the capacity to stimulate calcium release in organ culture of neonatal mouse calvaria

Summary In view of the possible association between ingestion of caffeine (a constituent of coffee, tea, and several beverages) and osteoporosis, we have studied the effect of caffeine on bone resorption in vitro. Caffeine caused a dose-dependent increase of the spontaneous release of ⁴⁵Ca from neonatal mouse calvarial bones. The effect of caffeine was less pronounced than that of parathyroid hormone (PTH), but of the same magnitude as that of theophylline, a structurally related methylxanthine. The enhancement of ⁴⁵Ca release induced by caffeine and PTH was observed in 5 days culture. In 2 days culture, however, only PTH stimulated mineral mobilization. The delayed stimulatory effect of caffeine in long-term cultures was abolished by indomethacin and flurbiprofen. In indomethacin-treated bones, however, caffeine potentiated the stimulatory effect on ⁴⁵Ca release induced by choleratoxin and forskolin. In contrast, caffeine did not potentiate ⁴⁵Ca release stimulated by PTH. These data show that caffeine can stimulate calcium release from bone in vitro and that this effect is due to potentiation of a stimulatory action of a bone resorptive agonist acting via the adenylate cyclase-cyclic AMP system.     

Isotopic exchange of ingested calcium between labeled sources. Evidence that ingested calcium does not form a common absorptive pool

Summary We studied the extent of salt dissociation during absorption of calcium from sources of differing absorbability by measuring fractional absorption from loads in the range of 200–300 mg in healthy adult women. Sources were labeled both intrinsically and extrinsically with⁴⁵Ca and⁴⁷Ca, respectively, and were fed alone and in combination with one another. We first confirmed our previous observation of superior absorbability of calcium oxalate over spinach calcium in a randomized cross-over design in 20 women. Spinach calcium exhibited only half the absorbability of the same load of calcium presented as the oxalate. Then, in 14 women fed spinach with both an intrinsic and an extrinsic label, apparent absorption of the extrinsic label averaged 0.130±0.041 and of the intrinsic label, 0.029±0.023. Thus, the extrinsic tag was partially, but not completely, bound by the spinach. In the same 14 women, milk absorption averaged 0.331±0.092 when ingested alone. However, when coingested with spinach, apparent milk calcium absorption fell to 0.267±0.079 and apparent spinach calcium absorption rose to 0.111±0.039. Thus, there was significant but incomplete label exchange between the two sources, indicating that at least some of the calcium from both sources enters a common preabsorptive, ionic pool. By contrast, we had previously shown no tracer exchange when labeled oxalate was co-fed with labeled milk. We conclude that (1) the presence of calcium as the oxalate in spinach is not a sufficient explanation for the poor absorbability of spinach calcium; and (2) oxalate calcium and spinach calcium are absorbed by different mechanisms, one involving a common preabsorptive pool and the other not. We suggest that oxalate calcium absorption is by passive diffusion of the intact complex and spinach calcium absorption by active transport of the free cation.     

The absorption of tricalcium phosphate and its acute metabolic effects

Summary The use of calcium (Ca) supplements by postmenopausal women is growing rapidly. A commercial preparation of tricalcium phosphate (TCP) is available in the USA. Depending on the relative absorption of Ca versus phosphate, a rise in serum phosphorus (P) could stimulate parathyroid hormone (iPTH) secretion. We therefore compared Ca absorption and the metabolic responses following TCP to that of Ca carbonate (CC) on separate occasions in each of 10 women, aged 22–40 years. The subjects were fasted overnight for 12 hours while good hydration was maintained. Following a 2-hour baseline-urine collection, 1200 mg calcium (as CC or TCP) was ingested and two 2-hour postload urine collections were made. Blood was drawn at 1, 2, and 4 hours after the Ca load. Serum (S) and urine (U) Ca, P, and creatinine, and U cyclic AMP (cAMP) were determined. iPTH levels following TCP were also measured. Ca absorption was determined by the postload rise in Uca above baseline. Uca excretion increased significantly and was accompanied by significant rises in Sca after both preparations. Following TCP, S and U phosphorus increased. Urinary cAMP did not change after either preparation, and iPTH levels fell after oral TCP. We conclude that Ca taken as TCP is absorbed adequately and, thus, despite a rise in the S phosphorus level does not stimulate parathyroid activity.