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At least 19 recordsLinked to original sources
PubMed1994

Bone repair in calcium-deficient rats: comparison of xylitol+calcium carbonate with calcium carbonate, calcium lactate and calcium citrate on the repletion of calcium.

The potential value of xylitol in calcium therapy was evaluated by comparing the effect of dietary xylitol (50 g/kg diet) + calcium carbonate with the effects of calcium carbonate, calcium lactate and calcium citrate on bone repair of young male rats after the rats consumed for 3 wk a calcium-deficient diet (0.2 g Ca/kg diet). After this calcium-depletion period, the rats were fed for 2 wk one of four diets, each containing 5 g Ca/kg diet as one of the four dietary calcium sources. The diet of the control animals was supplemented with CaCO3 (5 g Ca/kg diet) throughout the study. The Ca-deficient rats showed low bone mass, low serum calcium and high serum 1,25-dihydroxycholecalciferol, parathyroid hormone (1-34 fraction) and osteocalcin concentrations. They also excreted magnesium, phosphate and hydroxyproline in the urine in high concentrations, and had high bone alkaline phosphatase and tartrate-resistant acid phosphatase activities. Most of these changes were reversed by the administered of the calcium salts. The highest recoveries of femoral dry weight, calcium, magnesium and phosphate were observed in the groups receiving xylitol+CaCO3 and calcium lactate. Calcium lactate and calcium citrate caused low serum phosphate concentration compared with rats receiving CaCO3 and with the age-matched Ca-replete controls. Xylitol-treated rats excreted more calcium and magnesium in urine than did the other rats, probably due to increased absorption of these minerals from the gut. These results suggest that dietary xylitol improves the bioavailability of calcium salts.

Administration, Oral↗
PubMed1991

Calcium binding to fluorescent calcium indicators: calcium green, calcium orange and calcium crimson.

The recently introduced fluorescent calcium sensitive indicators calcium green, calcium orange and calcium crimson suggest important improvements and advantages to detect small calcium transients at low indicator concentrations. Thermodynamic dissociation constants and dissociation rate constants of calcium green, calcium orange and calcium crimson were measured by use of fluorescence titration and stopped flow fluorescence, respectively. Calcium binding to the indicators conforms to a 1:1 calcium:indicator complex although at high concentrations of calcium the fluorescence properties deviate somewhat from the behaviour predicted by the simple model. Dissociation of the calcium-indicator complex was found to be monoexponential under all conditions examined. The affinity for calcium of the three indicators generally increases with raising temperatures (Kd at 11.5 degrees C and 39.7 degrees C (nM): 261, 180 for calcium green; 527, 323 for calcium orange; 261, 204 for calcium crimson) and pH (Kd at pH 6.42 and 7.40 (nM): 314, 226 for calcium green; 562, 457 for calcium orange; 571, 269 for calcium crimson). The changes of the thermodynamic dissociation constant are mainly caused by changes of the association rate constant. The temperature dependence of calcium binding to the indicators revealed that this process is entropically favoured at ambient temperature.

Calcium↗
PubMed1995

Bioavailability of calcium from calcium carbonate, DL-calcium lactate, L-calcium lactate and powdered oyster shell calcium in vitamin D-deficient or -replete rats.

The bioavailability of calcium from various calcium sources in humans and animals has been the subject of investigation for many years and there is considerable controversy as to the relative bioavailability of different calcium salts. Most of the studies have used a calcium balance technique which has numerous problems in terms of performance and interpretation. Using a method for evaluating the efficacy of calcium from calcium salts used for plasma calcium metabolism and bone mineralization, we examined the bioavailability of calcium from four commercially available calcium salts, namely calcium carbonate, DL-calcium lactate, L-calcium lactate and powdered oyster shell-calcium in vitamin D-deficient or -replete rats. Among the calcium salts, the differences in bioavailability were small and not statistically significant as tested by analysis of variance in both groups of rats. Thus, we conclude that calcium is utilized to the same extent from calcium carbonate, DL-calcium lactate, L-calcium lactate and powered oyster shell-calcium in both vitamin D-deficient and -replete rats.

Animals↗
PubMed1989

[Ionized calcium, total calcium and albumin corrected calcium in the serum in 1213 patients with suspected calcium metabolic diseases. A prospective multicenter study].

The correlation between serum ionized calcium, serum total calcium and albumin corrected total calcium was investigated in a prospective multicentre investigation of 1,213 patients with suspected calcium metabolic disease. 31.0% of the patients were misclassified when serum total calcium was measured instead of serum ionized calcium. The diagnostic discrepancy between the two methods decreased with the calculation of albumin corrected total calcium or calculated ionized calcium (17.9%). On justing for the analytical error connected with the measurement of ionized calcium, 11.2% of the patients were still misclassified. It is not possible precisely to predict serum ionized calcium from the measurement of serum total calcium and we recommend measurement of serum ionized calcium in patients believed to have calcium metabolic disease.

Calcium↗
PubMed1995

Calcium requirements of lactating Gambian mothers: effects of a calcium supplement on breast-milk calcium concentration, maternal bone mineral content, and urinary calcium excretion.

The calcium requirement for prolonged lactation was investigated in a randomized supplementation study of Gambian mothers consuming a low-calcium diet (7.1 mmol/d, or 283 mg/d). Sixty women were studied from 10 d to 78 wk of lactation, receiving calcium or placebo for the first 12 mo. The supplement increased average calcium intake by 17.9 mmol/d (714 mg/d). Supplementation had no effect on breast-milk calcium concentration or on maternal bone mineral content. Urinary calcium output was higher in supplemented than in unsupplemented mothers by 1.18 mmol/d (47 mg/d), P < or = 0.005. Longitudinal changes in urinary calcium output and bone mineral content made a substantial contribution to calcium requirements for lactation. This study suggests that, in women with low calcium intakes, there is no direct benefit from increasing calcium intake during lactation, and that physiological mechanisms operate to furnish calcium for breast-milk production.

Adolescent↗
PubMed1989

Comparison of serum total calcium, albumin-corrected total calcium, and ionized calcium in 1213 patients with suspected calcium disorders.

The correlations between serum ionized calcium, serum total calcium, total calcium corrected for albumin and calculated ionized calcium were investigated in a prospective multicentre investigation of 1213 patients suspected of having calcium metabolic disease. Diagnostic discordance between serum total calcium and measured ionized calcium was found in 31% of the patients. With the calculation of albumin-corrected total calcium or calculated ionized calcium the discordance decreased to 17.9%. The diagnostic discordance which could be ascribed to the analytical imprecision (CV = 1.5%) amounted to only 6.7%. Although we found highly significant correlations between the parameters, a considerable scatter around the regression line made prediction of ionized calcium from albumin-corrected total calcium unreliable in many patients.

Algorithms↗
PubMed1987

Fasting and post-calcium load serum calcium, parathyroid hormone, calcitonin, in male idiopathic calcium urolithiasis--evidence for a basic disturbance in calcium metabolism.

In male healthy controls (n = 12), male renal calcium stone patients with either normocalciuria (NC; n = 12) or idiopathic hypercalciuria (I-HC; n = 12), all ideally matched for age and body weight, the response of variables of mineral metabolism to a calcium-rich oral test meal was evaluated. In all groups the postprandial urinary cyclic AMP is decreased as compared with fasting urine, indicating that the parathyroid glands are suppressible by oral calcium. However, in I-HC serum total calcium was significantly higher than in controls both basally and in the postprandial period; the associated mid-regional (bioinactive) serum parathyroid hormone was also elevated, but serum parathyroid hormone recognizing the amino terminal (bioactive) region of the molecule was significantly decreased. Also in I-HC, serum alkaline phosphatase is elevated, whereas urinary hydroxyproline in both fasting and postprandial urine is unchanged. The NC group holds an intermediate position between I-HC and controls. It can be concluded that I-HC subjects may suffer from a more basic disturbance of calcium metabolism which may help explain the nature of their hypercalciuria.

Adolescent↗
PubMed1988

Dose dependency of calcium absorption: a comparison of calcium carbonate and calcium citrate.

Calcium supplementation is recommended as a prophylaxis against bone loss. This study was performed to determine the dose dependency of calcium absorption in an attempt to derive an optimum dose schedule. Using the well-described oral calcium load technique, we measured the calcium absorption from three different calcium doses (0.5, 1.0, and 2.0 g) of both calcium carbonate and calcium citrate administered to 21 normal subjects (4 men and 17 women, 22-60 years). Nine subjects underwent two additional loads with 0.2 g of elemental calcium as calcium carbonate and as calcium citrate. The intestinal calcium absorption from calcium carbonate and calcium citrate was estimated from the rise in urinary calcium following oral ingestion of the respective calcium salt. The increment in urinary calcium post-load, reflective of intestinal calcium absorption, rose rapidly from 0 to 0.5 g calcium loads with only slight subsequent increases from the 0.5 g to 2.0 g calcium doses. Thus, results indicate that 0.5 g of calcium is the optimum dose of either calcium salt. Moreover, the increment in urinary calcium post-load was higher from calcium citrate than from calcium carbonate at all four dosage levels. The increment in urinary calcium (during the second 2 hr) following calcium citrate load (0.5 g calcium) was 0.104 +/- 0.096 mg/dl glomerular filtrate (GF), which was higher than that of 0.091 +/- 0.068 mg/dl GF obtained from 2.0 g calcium as calcium carbonate. These results confirm the superior calcium bioavailability from calcium citrate as compared with calcium carbonate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2000

Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems.

BACKGROUND: Calcium supplementation may prevent high blood pressure through a number of mechanisms and may help to prevent preterm labour. OBJECTIVES: The objective of this review was to assess the effects of calcium supplementation during pregnancy on hypertensive disorders of pregnancy and related maternal and child adverse outcomes. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group trials register and the Cochrane Controlled Trials Register and we contacted study authors. SELECTION CRITERIA: Randomised trials comparing at least one gram daily of calcium during pregnancy compared to placebo. DATA COLLECTION AND ANALYSIS: Eligibility and trial quality were assessed. Data extraction was carried out independently by two reviewers. MAIN RESULTS: Nine studies were included, all of good quality. There was a modest reduction in high blood pressure with calcium supplementation (relative risk 0.80, 95% confidence interval 0.73 to 0.88). The effect was greatest for women at high risk of hypertension (relative risk 0.35, 95% confidence interval 0.21 to 0.57) and those with low baseline dietary calcium (relative risk 0.49, 95% confidence interval 0.38 to 0.62). There was also a modest reduction in the risk of pre-eclampsia with calcium supplementation (relative risk 0. 72, 95% confidence interval 0.60 to 0.86). The effect was greatest for women at high risk of hypertension (relative risk 0.22, 95% confidence interval 0.11 to 0.43) and those with low baseline calcium intake (relative risk 0.32, 95% confidence interval 0.21 to 0.49). There was no overall effect on the risk of preterm delivery, although there was a reduction in risk amongst women at high risk of hypertension (relative risk 0.42, 95% confidence interval 0.23 to 0. 78). There was no evidence of any effect of calcium supplementation on stillbirth or death before discharge from hospital. REVIEWER'S CONCLUSIONS: Calcium supplementation appears to be beneficial for women at high risk of gestational hypertension and in communities with low dietary calcium intake. Optimum dosage requires further investigation.

Calcium↗
PubMed1980

Calcium movements promoted by vesicles in a highly enriched sarcolemma preparation from canine ventricle. Calcium-calcium countertransport.

Calcium uptake by vesicles in a highly enriched sarcolemma preparation from canine ventricle was found to be markedly stimulated by intravesicular calcium. Stimulation of calcium uptake appeared to be a saturable function of intravesicular calcium. Calcium efflux from the vesicles was stimulated by calcium in the reaction medium. Calcium uptake, supported by intravesicular calcium, and calcium efflux, stimulated by extravesicular calcium, were found to correspond on a one-to-one basis. Only small changes in net uptake or efflux were observed to occur in response to chemical gradients of calcium across the membrane. It was concluded, therefore, that under certain conditions, the major means for calcium movement across vesicles in the preparation is via a one-to-one exchange of calcium. Sodium was found to stimulate calcium uptake when present in the intravesicular space and to stimulate calcium efflux when present in the extravesicular space, but the effects of calcium plus sodium were not additive with respect to stimulating either calcium uptake or efflux. The effects of unlabeled calcium, strontium, barium, and magnesium on calcium uptake stimulated by intravesicular calcium and by intravesicular sodium were similar though not identical. The temperature dependence for calcium-stimulated and sodium-stimulated calcium movements was characterized by Q10 values of 1.27 and 2.06, respectively. Previous work has associated the sodium-calcium exchange reaction with the sarcolemma. It is argued that the present study, in turn, provides evidence that the calcium-calcium exchange reaction is also associated with the sarcolemma. In addition, the results of the study are consistent with the hypothesis that one membrane system can promote the exchange of either calcium for calcium or calcium for sodium.

Animals↗
PubMed1996

Abundant calcium homeostasis machinery in rat dental enamel cells. Up-regulation of calcium store proteins during enamel mineralization implicates the endoplasmic reticulum in calcium transcytosis.

UNLABELLED: Enamel cells handle large amounts of calcium, particularly during the developmental phase (termed maturation) when dental enamel is hypermineralized. The extent of intracellular calcium burden, and the nature of calcium homeostasis machinery used to accommodate it, are largely unknown. Here, the calcium-binding capacity of enamel cell cytosol was found to increase during development, in parallel with the putative transcellular flux of calcium. At maturation, the abundance of calcium-binding proteins in enamel cells exceeded that in brain and other established calcium-oriented tissues, which implies a large calcium burden. A search for likely cytosolic calcium transporters revealed only one high-affinity calcium-binding protein (12 kDa, distinguished from alpha-parvalbumin) that was up-regulated during maturation, but its low abundance (0.02% of soluble protein) precluded a major calcium transport or cytoprotective role. Two low-affinity calcium-binding proteins up-regulated during maturation (by 1.8-fold and 2.1-fold respectively) were identified as calreticulin and endoplasmin, both residents of the endoplasmic reticulum. Together, calreticulin and endoplasmin constituted an exceptionally high proportion (5%) of soluble protein during maturation, which gives an inferred calcium capacity 67-fold higher than that of the principal cytosolic calcium-binding protein. 28-kDa calbindin. Evidence that endoplasmin expression varied inversely with serum calcium concentration, and that the inositol trisphosphate receptor also was highly expressed during maturation, supported the novel hypothesis that non-mitochondrial calcium stores play a major role in transcellular calcium transport. IN CONCLUSION: (a) enamel cells contain a general high abundance of calcium homeostasis proteins, consistent with a heavy intracellular calcium burden; (b) the expression pattern (phenotype) of calcium-binding proteins varies with enamel cell function; (c) enamel cells appear to contain unusually large non-mitochondrial calcium stores; (d) contrary to the prevailing view that calcium passes mainly through the cytosol of calcium-transporting cells, the findings imply a route through the endoplasmic reticulum. This study gives novel information about how a highly calcium-oriented tissue avoids calcium toxicity, and provides a new focus for investigations into the mechanisms of transcellular calcium transport.

Animals↗
PubMed1990

Calcium metabolism in postmenopausal osteoporosis: the influence of dietary calcium and net absorbed calcium.

A group of 85 females aged 48-77 years with postmenopausal crush fracture osteoporosis were investigated using a 7 day combined calcium balance and calcium tracer kinetic turnover study to assess the influence of dietary calcium and net absorbed calcium on bone metabolism. During the study, patients were on their habitual diet, as determined by a prestudy registration. Dietary calcium was measured after double serving of all the meals. All urine and feces were collected and analyzed for calcium content. Bone mineralization rate and bone resorption rate were determined by applying the continuously expanding calcium pool model to the tracer kinetic data. Urine calcium excretion and net absorbed calcium were correlated (r = 0.64, p less than 0.0001) with the following equation: urinary excreted calcium (mmol/day) = 2.4 + 0.4 X net absorbed calcium (mmol/day). Dermal calcium loss was not correlated with net absorbed calcium or urinary calcium. The net amount of absorbed calcium necessary to balance urinary and dermal losses was calculated to be 4.2 mmol calcium per day. The daily calcium intake necessary for obtaining a net absorbed calcium in excess of the urinary and dermal calcium losses and thereby ensure skeletal integrity was estimated to be 34.2 mmol calcium per day compared to an average intake of 27.9 +/- 7.6 (mean +/- SD) mmol/day. Net absorbed calcium correlated negatively to bone resorption rate (r = -0.31, p less than 0.005) and positively to bone mineralization rate (r = 0.29, p less than 0.01) and to calcium balance (r = 0.66, p less than 0.0001). Dietary calcium intake and calcium balance correlated positively (r = 0.38, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed2000

Risk of calcium oxalate nephrolithiasis after calcium or combined calcium and calcitriol supplementation in postmenopausal women.

Although calcium supplementation can cause hypercalciuria, the risk of nephrolithiasis has been shown to decrease rather than increase among subjects who had a higher calcium intake. Hypercalciuria is also a well-established side effect of calcitriol administration. However, the risk of nephrolithiasis is not well defined. The present study was undertaken to prospectively determine the effect of calcium with or without calcitriol on physicochemical risk factors associated with calcium oxalate nephrolithiasis in Thai postmenopausal women with osteoporosis. Subjects consisted of 53 Thai women more than 10 years postmenopausal who were randomly allocated to receive 750 mg of calcium carbonate supplement alone (n = 28) or 750 mg of calcium carbonate plus 0.5 microg calcitriol (n = 25) daily. Mean +/- SEM for age was 65.3+/-1.1 years, body weight 53.5+/-1.3 kg. Urine samples for biochemical assays were collected at baseline and 3 months after treatment. Supersaturation for calcium oxalate stone formation was assessed from the 24 h urine constituents by the Tiselius's index, AP(CaOx). Three months of calcium supplement alone resulted in a modest, but not significant, increase in urinary calcium (baseline, 2.90+/-0.43 mmol/day; after treatment 3.58+/-0.54 mmol/day) with no change in urinary oxalate, citrate or magnesium. In contrast, calcium together with calcitriol caused a significant increase in urinary calcium (baseline, 2.87+/-0.41 mmol/day; after treatment, 4.08+/-0.57 mmol/day; p < 0.05). No significant change in other urine constituents after treatment with calcium and calcitriol was detected. Therefore, AP(CaOx) did not significantly increase either after calcium alone (baseline, 1.17+/-0.39; after treatment, 1.36+/-0.28) or after calcium plus calcitriol (baseline, 1.09+/-0.17; after treatment, 1.09+/-0.19). However, after treatments, 12 subjects (23%)--6 receiving calcium supplement alone and 6 receiving calcium plus calcitriol supplement--had high AP(CaOx) values (greater than the upper limit of 95% Cl for AP(CaOx) derived from non-stone-forming Thai women). The post-treatment/baseline ratio was 3.21+/-0.74 for urinary calcium, 1.01+/-0.19 for urinary oxalate, and 2.23+/-0.42 (median 1.15) for AP(CaOx). The post-treatment/baseline ratio of calcium, but not for urinary oxalate, had a significant correlation with the post-treatment/baseline ratio of AP(CaOx). Our findings suggest that the alteration in the risk of calcium oxalate nephrolithiasis based on urinary composition is related to the alteration in urinary calcium. The risk of calcium oxalate nephrolithiasis does not increase significantly after calcium or combined calcium and calcitriol supplement in the majority of postmenopausal women with osteoporosis.

Aged↗
PubMed1988

The bioavailability of calcium in spinach and calcium-oxalate to calcium-deficient rats.

We estimated the utilization of calcium in spinach and calcium-oxalate to calcium-deficient rats, and the effect of oxalic acid on absorption of dietary calcium by using calcium-deficient rats. The body weight gain of the calcium-deficient rats for 8 days receiving a calcium-deficient diet supplemented with raw-powdered spinach (R-sp), boiled-powdered spinach (B-sp), or calcium-oxalate (Ca-ox), and a control diet supplemented with oxalic acid (OX-C) were 4.8, 2.8, 4.9, and 5.1 g, respectively. The calcium content in the liver and kidney of the rats receiving R-sp, B-sp, Ca-ox, and OX-C diets significantly increased as compared with the calcium-deficient rats. Significant differences in the liver calcium levels were not observed among the rats receiving various additional diets, though the content in the kidneys of the rats receiving R-sp, B-sp, Ca-ox, and OX-C diets were 28.0, 21.5, 0.11, and 0.59 mg, respectively. An especially large amount of calcium was accumulated in the kidneys of the rats receiving R-sp and B-sp diets. The calcium concentration in the serum of the rats receiving Ca-ox and OX-C diets was higher than the calcium concentration in the serum of the R-sp, B-sp, and calcium-deficient rats. The calcium content in the left tibiae of the rats receiving Ca-ox and OX-C diets was higher than that of the rats receiving R-sp and B-sp diets. The breaking force of the right tibiae of the rats was highest in the OX-C group, and higher in the R-sp and Ca-ox groups than the breaking force of the right tibiae of the rats fed on B-sp diet. The alkaline phosphatase activity in the small intestines of the rats rose in the order of the R-sp, B-sp, and Ca-ox groups, although significant differences of the activity were not observed between the Ca-ox and the OX-C groups. The calcium retention of the rats receiving the calcium-deficient, R-sp, B-sp, Ca-ox, and OX-C diets was -18.5, 35.2, 25.6, 41.6, and 45.8%, respectively. About 35% of the calcium in the spinach was absorbed by the calcium-deficient rats, and oxalic acid depressed the calcium absorption in the rats.

Absorption↗
PubMedDate not supplied

Acute biochemical variations induced by calcium citrate and calcium carbonate in Type 2 diabetic patients: impaired calcium absorption in Type 2 diabetic patients with prolonged gastric emptying time.

Calcium supplementation is important in the treatment of osteoporosis, a disease that may also occur in diabetic patients. The acute effects of calcium supplementation and their relationship to gastric emptying time, however, have rarely been studied in type 2 diabetic patients. We evaluated the acute biochemical variations induced by the administration of two different calcium preparations, calcium citrate and calcium carbonate, in 16 (male/female: 13/3) Chinese diabetic patients. Serum free calcium, intact parathyroid hormone (i-PTH), and amount of urinary excretion of calcium (uCal/uCr) were evaluated after a single dose of 1200 mg of elemental calcium in each preparation. The free calcium levels did not change significantly in either group. However, significant suppression of i-PTH after calcium citrate administration at 1 h (17.1+/-2.0 pg/ml, P=.023), and after calcium carbonate administration at 2 h (14.2+/-2.5 pg/ml, P=.000), was noted when compared with individual basal level (21.2+/-2.5 and 19.3+/-2.4 pg/ml, respectively). The suppressive effect on i-PTH lasted for 6 h after calcium citrate and 5 h after calcium carbonate preparation of the 6-h study period. After administration of calcium citrate, the uCal/uCr of 2-to-4-h collection was significantly higher than that of the basal and 0-to-2-h collections: 0.25+/-0.04 vs. 0.19+/-0.03, P=.025; and 0.25+/-0.04 vs. 0.19+/-0.02, P=.014, respectively. A similar finding was observed for calcium carbonate: 0.23+/-0.03 vs. 0.18+/-0.02, P=.019; and 0.23+/-0.03 vs. 0.18+/-0.02, P=.011, respectively. We conclude that, in this group of Chinese type 2 diabetic patients in our study, the oral administration of 1200 mg elemental calcium in either calcium citrate or calcium carbonate preparation can induce a significant suppression of i-PTH. This may be helpful in preventing or treating osteoporosis. A prolonged gastric emptying time in these diabetic subjects may contribute to the non-significant alteration in free calcium levels after the administration of either calcium preparation.

Administration, Oral↗
PubMed1994

Dietary calcium chloride vs. calcium carbonate reduces urinary pH and phosphorus concentration, improves bone mineralization and depresses kidney calcium level in cats.

The effect of dietary calcium chloride vs. calcium carbonate on mineral metabolism was studied in cats. Ovariectomized cats and female kittens were fed purified diets with a normal calcium level (9.5 mmol Ca/MJ) but containing either calcium carbonate or calcium chloride, or were fed diets with a high calcium level (17.7 mmol Ca/MJ) containing either calcium carbonate alone or equimolar amounts of both calcium carbonate and calcium chloride. A 4 x 4-wk cross-over study using adult cats and a 31-wk parallel study using kittens were conducted. Calcium, phosphorus and magnesium balances were established regularly. In the course of the experiment with the kittens, blood samples were taken and X-ray photographs of the tibiae made. At the age of 39 wk, the kittens were killed, and organs and bones were collected. In both adult cats and kittens fed the high calcium diets, urinary concentrations of magnesium and phosphorus and apparent absorption of these minerals were lower than after feeding the normal calcium diets. Urinary pH and phosphorus concentration were lower in cats and kittens fed diets with calcium chloride instead of calcium carbonate. Body weight gain and tibia growth in the kittens tended to be greater after feeding the diets with calcium chloride. Calcium chloride vs. calcium carbonate and also supplemental calcium chloride in the high calcium diet significantly stimulated femur density and reduced renal calcium concentration.

Aging↗
PubMed1996

Plasma membrane calcium pump-mediated calcium efflux and bulk cytosolic free calcium in cultured aortic smooth muscle cells from spontaneously hypertensive and Wistar-Kyoto normotensives rats.

OBJECTIVE: To compare the efficacy of the calcium pump-mediated calcium efflux pathway in spontaneously hypertensive rats (SHR) with that in Wistar-Kyoto normotensive rats (WKY), at rest and after angiotensin II stimulation. DESIGN: The intracellular free calcium concentration and calcium-45 efflux were measured in parallel, in cultured aortic smooth muscle cells isolated from 10-week-old male SHR and WKY rats. METHODS: The intracellular free calcium concentration and calcium-45 efflux were studied in confluent vascular smooth muscle cells in culture. Experiments were performed in the absence of added extracellular calcium and sodium. Fura-2 was used to measure basal and angiotensin II-stimulated intracellular free calcium concentration. Effluxed calcium-45 was measured over 5s intervals to determine basal and angiotensin II-stimulated calcium efflux rates in SHR and in WKY rats. RESULTS: No significant difference between SHR and WKY rats was observed in basal intracellular free calcium concentration or 100nmol/l angiotensin II-stimulated peak intracellular free calcium concentration. However, significantly elevated basal and 100 nmol/l angiotensin II-stimulated calcium-45 efflux rates were found in SHR. The calcium-45 efflux rates in SHR were elevated when the efflux was normalized with respect to the bulk intracellular free calcium concentration. The time taken to reach the maximum calcium-45 efflux rate after angiotensin II stimulation was reduced in SHR compared with that in WKY rats and was dose-dependent in both rat strains. CONCLUSION: The calcium-pump mediated calcium efflux pathway appears to be more efficient in SHR. This may be the result of post-translational modification, enhanced calcium pump sites in a critical region of the membrane, or the presence of a pool of calcium near the plasma membrane that is not readily detected by cytosolic Fura-2 but is higher in SHR both before and after angiotensin II stimulation.

Animals↗