Total Ca Levels Research Articles

Bone turnover in rats treated with 1,25-dihydroxyvitamin D3, 25-hydroxyvitamin D3 or 24,25-dihydroxyvitamin D3

Female rats were given 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), 0.25 microgram per 100 g body weight (bw), 25-hydroxyvitamin D3 (25(OH)D3), 1.7 micrograms/100 g bw or 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) 1.7 micrograms/100 g bw, subcutaneously three times a week for 12 weeks. Traditional variables pertaining to calcium homeostasis and growth, i.e. blood and urine calcium (Ca) and phosphate (P), serum levels of vitamin D3 metabolites parathyroid hormone, (PTH), calcitonin (CT), prolactin (PRL) and growth hormone (GH) were measured every four weeks. This data pool was correlated with bone matrix turnover parameters, i.e. serum levels of alkaline phosphatase (ALP) and urinary hydroxyproline (u-HYP) excretion. After 12 weeks of treatment, 1,25(OH)2D3 significantly enhanced serum total and ionized Ca, urine Ca and urine P, and also diminished urine cAMP due to reduced renal function (creatinine clearance). However, 25(OH)D3 administration had no such impact. 24,25(OH)2D3 opposed the effect of 1,25(OH)2D3 after 12 weeks by significantly augmenting serum P and diminishing serum levels of total Ca and ionized Ca. Cross sectional group analyses showed that circulating levels of ALP were directly related with serum 1,25(OH)2D3 and inversely related to serum 24,25(OH)2D3 and CT. Total u-HYP and per cent non-dialysable HYP (ndHYP) were reciprocally and positively correlated with serum PRL, respectively. However, no such relations were observed with serum GH. It appears that rats with elevated circulating levels of 1,25(OH)2D3 exhibit increased bone resorption, while augmented 24,25(OH)2D3 is associated with the opposite. Apparently, high bone turnover (i.e. reduced total urinary HYP and enhanced ndHYP) is associated with high serum PRL.

Calcium and the firmness of kiwifruit

Abstract The effect of calcium (Ca) concentration on the firmness of kiwifruit during cool-storage was investigated by (a) postharvest dipping of fruit in CaCl2, and (b) comparing endogenous Ca and firmness of fruit which differed in one of the following orchard or fruit variables: fruit size; crop load; position of the fruit on the vine; exposure to sunlight during growth; and irrigation treatments. Postharvest dipping of kiwifruit in 2,3,4, or 5% CaCl2 reduced the rate of fruit softening early in storage, resulting in fruit which were firmer after storage than control fruit. However, severe pitting of the fruit skin developed during storage as a result of dipping in 5% CaCl2. Total endogenous Ca levels in kiwifruit from several orchard sources ranged from 1.7 to 2.7 mg/g dry weight, but were not correlated with fruit firmness during storage. Furthermore, lines of kiwifruit which became particularly soft during storage had Ca concentrations similar to or even higher than lines of fruit which had remained firmer. These results are discussed in relation to the prediction of fruit firmness during storage, and the potential of developing commercial postharvest treatments for maintaining firmness of kiwifruit.

Short-term effects of carbetimer on calcium and bone metabolism in man

Carbetimer is a new antineoplastic agent whose limiting toxicity consists of dose- and treatment duration-dependent hypercalcemia. We examined the short-term effects of Carbetimer on calcium metabolism on days, 1, 3 and 5 during 11 5-day courses (6.5–8.2 g/m2/day given over daily 2-h infusions, q 3–4 weeks). Blood parameters were measured before and after Carbetimer, whereas urinary parameters were studied in three consecutive 2-h collections before, during and after Carbetimer infusions. Carbetimer effects were similar regardless of the infusion day. We found a consistent decrease of plasma ionized Ca (Ca2+) levels from 4.56 ± 0.05 mg/dl before infusion to 4.28 ± 0.06 mg/dl after infusion (P < 0.001) whereas total serum Ca (corrected for protein levels) did not change. The fall of Ca2+ stimulated parathyroid function, as suggested by the increased plasma PTH levels, the decreased serum phosphorus and TmP/GFR index, or the increased urinary phosphate and cyclic AMP excretion. Carbetimer infusions also induced a marked increase in urinary Ca excretion (expressed as mg Ca/mg creatinine) from 0.093 ± 0.011 before to 0.359 ± 0.042 during and 0.177 ± 0.031 after infusion (P < 0.001). These changes were best explained by Carbetimer-induced Ca chelation that we confirmed in vitro by incubating Carbetimer at various concentrations in whole blood for 2 h at 37°C, e.g. 2 mg of Carbetimer/ml lowered Ca2+ from 4.82 to 3.20 mg/dl without changing total Ca levels. On the other hand, a direct effect of Carbetimer on bone cannot be excluded since we observed an increase of serum osteocalcin levels from 2.0 ± 0.3 to 2.5 ± 0.4 ng/ml after infusion (P < 0.001). In summary, the short-term effects of Carbetimer on calcium metabolism markedly differ from the long-term effects. They mainly consist of a dose-related calcium chelation leading to a decrease in Ca2+ levels, an increase in urinary Ca excretion and a stimulation of parathyroid function.

Calciotrophic hormone levels and calcium absorption during pregnancy in rats

The mammalian maternal skeleton stores Ca during pregnancy perhaps for fetal skeletal mineralization in late pregnancy and milk production during lactation. The interrelationships between intestinal Ca absorption and hypertrophy and plasma levels of total Ca, ionized Ca, 25-hydroxyvitamin D3 [25(OH)D], 1,25-dihydroxyvitamin D3 [1,25(OH)2D], and parathyroid hormone (PTH) were determined at different stages of pregnancy in rats. By midpregnancy and before fetal skeletal mineralization, plasma ionized Ca levels, Ca absorption by duodenal tissue in vitro, Ca absorption by the duodenum in situ, and duodenal wet weight were increased and 25(OH)D was decreased. Later in pregnancy, during fetal skeletal mineralization, 1,25(OH)2D and PTH levels were also substantially increased and total serum Ca levels decreased. These data demonstrate changes by midpregnancy, before fetal skeletal mineralization, in maternal mineral homeostasis concomitant with known changes in skeletal metabolism. Some of the early changes in mineral metabolism may occur independent of the vitamin D and PTH endocrine system.

Cyclic nucleotides and the rapid inhibitions of bone45Ca uptake in response to bovine parathyroid hormone and 16,16-dimethyl prostaglandin E2 in chicks

Intravenous injection of chicks with bovine parathyroid hormone (1-34) (3.3 micrograms/100 g body wt.) or 16,16-dimethyl PGE2 (5 micrograms/100 g body wt.) caused rapid (3 minute) net inhibition of 45Ca uptake into femur and calvarium. These agents also elevated bone adenosine 3',5'-cyclic monophosphate (cAMP) but not guanosine 3',5'-cyclic monophosphate (cGMP) levels at this time. Methylxanthine phosphodiesterase inhibitors (MXPI), caffeine, theophylline, and 3-isobutyl-1-methylxanthine (IBMX) (0.3-5 mg/100 g body wt.) similarly inhibited net 45Ca uptake into femur and to a lesser extent calvarium. Plasma 45Ca and total Ca levels were unaltered or showed a slight tendency to be increased over control values 3 minutes after injection. However, the effects of the non-MXPI, dibutyryl-cAMP (0.5-5 mg/100 g body wt.) on bone 45Ca uptake were negligible. Of the MXPI, only IBMX elevated total cAMP levels in chick bone at 3 minutes. These data implicate but do not confirm a mediatory role for cAMP in the rapid inhibitory actions of PTH and PGEs on bone net 45Ca uptake in chicks.

Quantitative imaging of free and total intracellular calcium in cultured cells.

Techniques of fluorescence and ion microscopies were combined to study the free [Ca2+] and total Ca in NIH 3T3 fibroblast and L6 rat myoblast cells. Free Ca2+ measurements with the Ca2+ indicator fura-2 and digital imaging reveal an inhomogeneous distribution of free cytoplasmic Ca2+ in both cell lines. Fura-2 also reveals a difference in free Ca2+ activity between the nucleus and cytoplasm of cells. Ion microscopic observations on sister cells show that total Ca in the cytoplasm is also inhomogeneously distributed and that mean cytoplasmic levels of total Ca are higher than levels in the nuclei. In the nuclei of NIH 3T3 cells, the mean free [Ca2+] and total [Ca] were 110 +/- 30 nM and 225 +/- 43 microM, respectively, while regions in the cell cytoplasm contained up to 490 +/- 270 nM free [Ca2+] and 559 +/- 184 microM mean total [Ca]. Intracellular total Ca was greater than 3 orders of magnitude higher than intracellular free Ca2+ in either nuclear or cytoplasmic compartments. Perinuclear cytoplasmic regions in 3T3 cells contained higher free and total Ca than the cell nucleus. Loading of cells with fura-2 did not modify the subcellular distribution of total K, Na, Ca, or Mg. This combination of two powerful ion imaging techniques provides a comparison between free and total calcium in cells and introduces a different approach for examining the role of this important element in cell physiology.

Ion interactions in calcium‐efficient and calcium‐inefficient tomato lines1

Abstract Two Ca‐efficient and 3 Ca‐inefficient tomato lines selected on the basis of dry matter production, Ca concentrations in tissues, and severity of Ca deficiency symptoms were grown in nutrient solutions containing 6 levels of total Ca ranging from 15 to 365 mg in 70 mg increments. All lines responded to increased Ca supply by increasing in dry weight and by accumulating Ca. The critical Ca concentrations in the shoots were 0.25% and 0.40% on a dry weight basis for the efficient and inefficient lines, respectively. Concentrations of Ca, K, Mg, P, and NO3 ‐ were lower in shoots and except for Mg were lower in roots of efficient plants than in the inefficient plants. For all lines as more Ca was available in the media and as Ca increased in the shoots and roots, the concentrations of the nutrients other than Ca declined. The declines in concentrations of K and Mg were not due to dilution by higher dry matter production in the efficient lines relative to the inefficient ones, although the total accumulation of Ca, P, and NO3 ‐ did not vary with Ca supplied. Antagonism among cations may account for differences in efficiency among lines of tomato.

Effect of dietary calcium on selenium retention in postweaning swine.

Two experiments were conducted to evaluate the effect of dietary Se and Ca on Se utilization in postweaning swine. Two levels of dietary Se (.3 or 5.0 ppm) supplemented as sodium selenite and four levels of total dietary Ca (.50, .80, 1.10 or 1.40%) in a 20% protein, corn-soybean meal diet were evaluated. Inorganic Ca was supplied from dicalcium phosphate and limestone. In Exp. I, 135 pigs weaned at 4 wk of age were allotted by sex, litter and weight and fed a basal diet for 7 d and then their treatment diets for a 28-d period. Plasma and tissue were collected at the end of the trial for Se concentration and glutathione peroxidase (GSH-Px) activity. Dietary Ca had no effect on gain or feed measurements but 5.0 ppm Se depressed daily gain slightly. When 5.0 ppm dietary Se was fed, there resulted higher liver, kidney, heart and longissimus muscle Se concentrations than when .3 ppm was provided, but dietary Ca had no effect on tissue Se values within each dietary Se level. Plasma GSH-Px increased when higher dietary Se was provided, whereas neither heart nor liver GSH-Px activity was affected by dietary Se or Ca level. In Exp. II, a 5-d balance trial was conducted with 32 barrows after adjustment to their treatment diet for a 28-d period. Selenium retention increased quadratically as dietary Ca increased, whereas Ca retention was not affected by dietary Se. These results suggest that low dietary Ca levels may reduce total Se retention but not Se metabolism within body tissue.

前立せんしゅよう患者の骨代謝

Radial bone mineral content (BMC) was measured by 125-I single photonabsorptiometry in patients with prostatic cancer and benign prostatic hypertrophy. The correlations between radial BMC and serum Ca, Pi and alkaline phosphatase were also investigated from the standpoint of bone metabolism. A slight increase of radial BMC was demonstrated in patients with prostatic cancer as well as prostatic hypertrophy, suggesting the existence of a prostatic osteoblast stimulating factor in the patients with prostatic tumors. But regarding the effect of bone metastasis of prostatic cancer on radial BMC, no significant increase in radial BMC was indicated in the patients with bone metastasis. Serum levels of total Ca and inorganic phosphorous were slightly lower in prostatic cancer than in benign prostatic hypertrophy. No changes of radial BMC and serum Ca and Pi levels were demonstrated after orhiectomy and hormonal theraphy.

Short-term changes in Ca, Pb, Zn and Cd concentrations of the garden snail Helix aspersa Müller from a central London car park

Helix aspersa were collected from a car park with a high degree of Pb and Zn pollution over a period of 102 days following the end of aestivation. Analysis of whole soft tissues demonstrates a high variability in both Pb and Ca levels in the short term, possibly associated with shell formation. Pb, Zn and Ca concentrations are also shown to vary with age-class. No simple relationship between total Ca and total heavy metal levels was found, and it is concluded that Ca does not account for the high variability between individuals. The rate of loss of each heavy metal is shown to vary with age-class.

STRONTIUM-CALCIUM RELATIONSHIP IN CANADIAN SOILS

The correlation coefficient between total Ca and total Sr levels in 162 soil samples widely distributed in Canada was 0.43. Removal of data for 23 calcareous samples resulted in a markedly higher correlation coefficient (0.87, P &lt; 0.01). The corresponding regression equation Sr (ppm) = 75 + 131 Ca(%) is useful for estimating the Sr level of non-calcareous soil samples.

Parathyroid hormone and calcitonin levels in vitamin D deficient rickets

In six infants aged between 5 and 8 months with vitamin D deficient rickets, we have studied blood levels of calcium (Ca), phosphorus (P), alkaline phosphatase, immunoreactive parathyroid hormone (PTH) and calcitonin (CT), as well as urinary excretion of Ca, P, hydroxyproline and cyclic AMP, both under basal conditions and during a 4h infusion of 20 mg/kg 10% Ca gluconate in normal saline. Under basal conditions all the infants had high alkaline phosphatase (range: 470--770 U.I./1); PTH (range: 620--1200 pg Eq/ml) and CT (range: 440--750 pg/ml) but two infants had hypocalcaemia and four had normocalcaemia and hypophosphataemia. The urinary Ca excretion was low whereas the urinary P, hydroxyproline and cyclic AMP excretions were high. During Ca infusion the total serum Ca and CT levels increased, while alkaline phosphatase and PTH fell. After the end of the infusion, CT levels fell perceptibly; phosphaturia, hydroxyprolinuria and cyclic AMP decreased on the day of the infusion.

1033 IONIZED Ca (iCa) IN RELATION TO GESTATIONAL AGE

Previous studies of serum Ca in relation to gestational age have not examined iCa, the physiologically active fraction of circulating Ca. Forty-three infants with birth weights appropriate for gestational age were studied from birth to 72 hrs.of age Ionized Ca was determined by the Orion 99-20 flow-thru electrode, standardized with aqueous and serum standards. Normal serum iCa in 35 young adults ranged from 3.6 to 4.5mg/dl; in 34 well full term infants on day 3, iCa ranged from 3 to 4mg/dl. Fifteen of 43 (35%) of study infants were “hypocalcemic” (serum iCa ≥3mg/dl) on at least one occassion in the first 3 days of life. Serum iCa levels were correlated with total Ca levels (correlation r=0.588,p<.001). At birth, umbilical venous serum iCa was correlated with simultaneous maternal iCa (r=0.658,p<0.01), but significantly higher than maternal values (4.7±.11mg/dl, mean±SE, vs. 4.1±.07, respectively, paired t p<.001). A greater decrease of serum iCa from birth to 24-48 hrs. was related to a higher cord blood iCa (r=0.611, p<.011). Serum iCa at 24 hrs correlated with gestational age (r=0.43,p<.05) and the amount of bicarbonate received/kg body weight/first 24 hrs. (r=.527, p<.01) but not with birth weight (r=.210). Serum iCa at 24 hours was related to serum iCa at 48 and 72 hrs. (r=.794,.709). Thus, serum iCa at birth is correlated with, but higher than simultaneous maternal iCa; serum iCa at 24 hrs. of age is significantly correlated with gestational age.

1028 EFFECT OF INCREASED Ca, P INTAKE ON BONE MINERALIZATION IN PRETERM AGA INFANTS

The effect of Ca supplementation in prematures on bone mineral content (BMC) has not been quantitated in vivo. BMC (radius and ulna) was measured by photon absorptiometry in 42 term and 39 preterm AGA infants. Preterm infants were divided into 2 groups: “A” (n=30) 29-36 wks.gestation, fed Similac 20 cal/oz; and “B” (n=9) 28-36 wks. fed a modified Similac 20 cal/oz (126 mg Ca and 63 mg P/dl). Ionized Ca (iCa) total Ca, 25 hydroxy vitamin D, parathyroid hormone, Mg and P were measured every 2-4 wks. for 12 wks. In term and preterms, BMC at birth correlated with gestation (r=.821, p<.001). The regression line of BMC vs. gestation in these infants represents “normal” “intrauterine” bone mineralization (IUBMC). In “A”, postnatal BMC was less than IUBMC (covariance F = 12.5, p<.001). In “B”, BMC increased significantly with postnatal age (r=.627, p<.05) and did not differ from IUBMC (p>.05); at 37-38 wks. postconceptual age BMC was .072 gm/cm±.002 SEM, similar to BMC in infants born at 37-38 wks. In “B”,daily Ca intake was 157±22 mg/kg/day in the first wk. and 250±7 in the 2nd and subsequent wks. Serum total Ca levels were 9.8±.3mg/dl; iCa levels were 4.4±.lmg/dl.No clinical complications were observed in “B”. We conclude that 1) in premature infants on routine formula, extrauterine bone mineralization lags significantly behind intrauterine bone mineralization and 2) increased Ca and P intakes might result in bone mineralization rates similar to intrauterine mineralization rates.

Iron deficiency symptoms of carp.

Carp, Cyprinus carpio, were fed on the diets with and without supplemental iron over a 105 day period. No significant differences were recognized between the two groups in the following determinations: the growth rate, condition factor, feed efficiency, and the percentages of liver, spleen, and heart weight to body weight; the blood serum levels of total protein, total cholesterol, total bilirubin, BUN, glucose, and Ca and inorganic P; and the activities of enzymes such as GOT, GPT, ALP, LDH, and LAP in the blood serum. However, in the group fed the diet without the iron supplement, the specific gravity, Hb content, and Ht value of blood, the mean corpuscular constants, and the mean corpuscular diameter of minor length were lower, and the percentage of immature erythrocytes was higher than those of the group fed the iron-supplemented diet. These findings show that carp fed the diet without iron supplementation manifest a hypochromic microcytic anemia.

Parathyroid hormone and calcitonin secretion in uraemic infants

In six infants aged between 4 and 8 months with chronic renal failure, we have studied blood levels of calcium (Ca), phosphorus (P), alkaline phosphatase, immunoreactive parathyroid hormone (PTH), and calcitonin (CT), as well as urinary excretion of Ca, P, hydroxyproline and cyclic AMP under basal conditions and during an infusion of 20 mg/kg of 10% Ca gluconate in normal saline over 4 h. Under basal conditions four infants had normal serum Ca and P values, alkaline phosphatase levels at the upper limit of normal, and very high PTH (range: 1450--2550 pg Eq/ml) and CT (range: 700--1900 pg/ml) levels. The urinary Ca excretion was low, whereas the urinary excretion of P, hydroxyproline and cyclic AMP was high. During Ca infusion, the total serum Ca and CT levels increased, PTH fell without however reaching the normal upper limit, and urinary P and cyclic AMP excretion decreased. In two infants with osteodystrophy and the highest levels of PTH (2900 and 3500 pg Eq/ml respectively) there was no suppression of PTH during Ca infusion.

Photosynthesis of, and 14CO2‐Photosynthate Translocation from, Calcium‐deficient Leaves of Crops1

Limited information is available on the role of Ca in net photosynthesis (Pn) and 14C translocation. This research was done to determine the influence of the removal of Ca supply from 2‐month old soybean (Glycine max (L) Merr. ‘Hampton 266A’), peanut (Arachis hypogaea L. ‘Florunner’), and cotton (Gossypium hirsutum L. ‘Goker 310’) plants on Pn, 14C translocation, and Ca concentration. Removal of Ca from the nutrient solution did not influence Pn of any of the species until Ca dificiency was visible in the measured leaf. Critical levels of total Ca on Pn were near 0.3% but acetic acid extractable Ca was 0.09 to 0.23% indicating that Ca requirements for Pn may be in micronutrient amounts. Short‐term translocation of 14C from Ca‐deficient leaves was 36% higher for peanut and 56 and 31% lower for soybean and cotton, respectively, compared to plants of the same species supplied with Ca.

Alterations in skeletal calcium and phosphorus in dysfunction of the parathyroids.

Changes in the bones of hyperparathyroid patients were studied with the new technique of total-body neutron activation analysis. Demineralization of the skeleton occurred in most hyperparathyroid patients as has been previously noted. The further finding of no loss of skeletal mass in some patients reinforces a previously formed hypothesis of the existence of two clinically different types of hyperparathyroidism. A low mean P/Ca ratio was observed, possibly the result of an inhibition of proximal tubular resorption corresponding to the increased PTH level. No significant change in the total Ca level was observed in several patients studied at 6-15 months following surgical removal of the parathyroid adenoma. Hypoparathyroid patients exhibited an increase in body Ca in terms of the expected value (Cap). Gains in the total body Ca level in postoperative hypoparathyroidism were modest compared to a marked increase in a patient with idiopathic hypoparathyroidism. The results are consistent with the reduction ...

Studies on some deep sandy soils in Cape York Peninsula, North Queensland. 2. Plant nutrient status

The nutrient status of the deep siliceous sands which cover an extensive area in Cape York Peninsula has been studied in glasshouse and field experiments. Using Townsville stylo (Stylosanthes humilis) as a test legume, the soils were found to be extremely deficient in P and S, and moderately so in Zn, Cu, and K. Responses to Mo were found on most of the eight soils tested in the glasshouse but these were not confirmed at the field site in either of the two growing seasons. There was little response to Ca (lime) in spite of the very low levels of total and exchangeable Ca in these soils. Suggested reasons for this are the known tolerance of tropical legumes to low Ca supply and the fact that exchangeable Ca, although low, represented a fairly high percentage of the total exchange capacity. Levels of total N in these soils were also very low and the native grasses were able to absorb only 15 kg N ha-1 in an entire growing season. Two samples of rock phosphate (from north-western Queensland and Christmas Island) were found to be very poor alternatives to superphosphate, at least in the first season. In spite of the extreme infertility of these soils, very high levels of pasture production (&gt; 10,000 kg of Townsville sty10 ha-1) could be achieved in well-fertilized pastures.

Skeletal metabolism and body composition in acromegaly.

The effect of hypersomatotropism on skeletal metabolism and body composition was investigated in ten acromegalic individuals. The techniques of whole body counting, total body neutron activation analysis, 47Ca tracer kinetics, quantitative microradiography and measurement of cortical and trabecular thickness of bone biopsy specimens were employed. The profound effect of growth hormone on protein metabolism was confirmed by the increase in mean 40K and total body N. Total body levels of Cl and P were also increased. Total body Na was increased as was the Na/K ratio indicating a relative increase in total body Na when related to lean body mass. There was no correlation between total body Na or Na/K and hypertension. 47Ca tracer kinetics revealed an increased exchangeable pool and increased bone turnover. Only 1 of 6 patients studied was definitely in positive Ca balance. Mean total body Ca was 9% higher than the predicted values calculated on the basis of height. However, normalization of total body Ca by relating it to lean body mass (Ca/K), revealed a reduced Ca/K ratio in 4 subjects. Although this may be the result of an increase in soft tissue mass that is greater than the increase in skeletal mass, two patients had total body Ca levels which were less than the values predicted on the basis of height. These two subjects must be considered to have osteopenia. Quantitative microradiography of bone biopsies obtained from the iliac crest showed normal bone formation levels and increased resorption levels as is seen in osteoporosis. However, the cortical thickness was normal in all patients studied and the trabecular width was normal or increased. It is likely that cortical thickness is maintained by increased periosteal apposition.