Plasma Ca Levels Research Articles

A New Animal Model to Assess Angiogenesis and Endocrine Function of Parathyroid Heterografts In Vivo

It is still a matter of investigation how angiogenesis and restoration of gland perfusion determine graft function after free parathyroid autotransplantation. We provide a new animal model allowing simultaneous and repetitive in vivo assessment of angiogenesis and endocrine function of parathyroid transplants. Fresh human parathyroid tissue from patients with secondary hyperparathyroidism was grafted into dorsal skinfold chamber preparations of athymic nude mice (CD1-nu; n=8). Equivalent pieces of the same human donor specimens were heat-inactivated and served as control grafts (n=7). In all animals receiving parathyroid transplants, intact human parathyroid hormone levels were detectable by species-specific enzyme-linked immunosorbent assay analysis of plasma samples on day 5 after transplantation and increased by 2.5-fold over the observation period (19 days) in contrast with controls. Plasma Ca levels revealed no differences between the groups. On day 5 after transplantation, intravital fluorescence microscopy revealed murine angiogenic microvessels sprouting along nonperfused human donor vessels, and 1 week later functional microvasculature was established in all parathyroid transplants. Histologic analysis revealed well-vascularized endocrine tissue. In contrast, control grafts were necrotic and partly resorbed; they exhibited no angiogenic activity or well-vascularized fat cells indicating fatty degeneration. In addition, species-specific Western blot analysis revealed vascular endothelial growth factor expression of parathyroid transplants rather than functional vessel density as the functional parameter of angiogenesis determining transplant function in vivo. This model may serve to understand mechanisms associated with specific parathyroid transplant angiogenesis and its significance for transplant function to optimize clinical success of autotransplantation in therapy-resistant patients.

Calcium metabolism in cows receiving an intramuscular injection of 1,25-dihydroxyvitamin D3 combined with prostaglandin F2alpha closely before parturition

To determine the effect of exogenous 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] combined with induced parturition on calcium (Ca) metabolism, cows received a single intramuscular injection of 1,25(OH)2D3 and prostaglandin F(2alpha) (PGF(2alpha)) closely before calving. Ten late-pregnant, multiparous Holstein cows were assigned to 1,25(OH)2D3 group (five treated with both 1,25(OH)2D3 and PGF(2alpha)) and control group (five treated with PGF(2alpha)). 1,25(OH)2D3 group showed an increase in plasma Ca concentration around parturition, whereas control group revealed a decrease in plasma Ca level. Plasma Ca concentration in 1,25(OH)2D3 group were significantly higher than that in control group during -0.5 to 3 days after parturition.

Inhibition of Growth Hormone Secretion in Mild Primary Hyperparathyroidism

Introduction: Impairment in growth hormone (GH) secretion has been reported to occur in primary hyperparathyroidism (PHP) with strikingly elevated (>150 pg/ml) plasma PTH and free Ca levels. Patients with these characteristics are relatively few, whereas the great majority of patients with biochemically diagnosed PHP are asymptomatic and show borderline or slightly elevated plasma PTH and Ca levels. We wondered whether also patients in these latter conditions show a defective GH secretory pattern. Methods: In order to answer this question, 8 female subjects (mean age ± SE: 44 ± 1.3 years) were selected at the time of a checkup examination from a larger population of persons in fairly good clinical condition. Inclusion criteria were plasma PTH values slightly above the normal range (up to 50% higher than the maximum limit) with free Ca levels in the upper normal range or slightly higher (experimental group). Normal values in our laboratory are ionized calcium: 1.22–1.42 mmol/ml and plasma PTH: 12–72 pg/ml. A group of 15 age-matched healthy women with plasma PTH and Ca levels in the middle normal range and significantly lower than values found in the experimental group was also selected and used as control. Experimental and control groups were tested with arginine [0.5 mg/kg body weight (BW)] infused intravenously over 30 min and arginine plus GH-releasing hormone (GHRH; 1 µg/kg BW in an intravenous bolus injection). The GH responses to these challenging stimulations were compared between groups. Results: Basal serum GH values were similar in all subjects. Both arginine and arginine plus GHRH induced a significant GH rise in both groups; however, the GH responses were significantly lower in the experimental than in the control group. Mean GH peak was 27.7 and 14.6 times higher than baseline after arginine and 57.5 and 26.6 times higher than baseline after arginine plus GHRH in the control and experimental group, respectively. No significant correlation was observed between PTH or Ca levels and the GH responses to challenging stimuli in any group. Conclusion: These data show that impairment in GH secretion is associated with slightly elevated levels of PTH in the presence of serum Ca values in the upper normal range. GH responses to stimulations were reduced by about 50% in our hyperparathyroid subjects. A long-time duration of this relatively small decline of GH secretory activity may be supposed to contribute to age-related catabolic processes in a large number of patients with mild primary hyperparathyroidism.

Technical Note: Vaginal Absorption of 1,25(OH)2D3 in Cattle

Although exogenous 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] administered via intravenous, intramuscular, and oral routes has been tested for efficacy in preventing parturient hypocalcemia in dairy cows, there are few reports concerning intravaginal administration. For this study, 1,25(OH)2D3 was administered via the bovine vaginal lumen, and subsequent changes in blood chemistry, including levels of 1,25(OH)2D3 and several minerals, were measured to confirm vaginal absorption. Each of 5 heifers received a single intravaginal dose of 1μg of 1,25(OH)2D3/kg body weight; a single control heifer received the ethanol carrier alone. In heifers receiving 1,25(OH)2D3, the plasma 1,25(OH)2D3 levels increased markedly from baseline (88.3±20.3 pg/mL) within 2h and reached a peak at 6h after treatment (1967.4±1139.6 pg/mL). Plasma Ca levels increased from baseline (10.4±0.4 mg/dL) to a peak of 11.96±0.7 mg/dL at 24h. The levels of inorganic phosphate in plasma increased over time from 7.3±0.5 to 8.1±0.8 mg/dL by 6h and were maintained at a plateau level (9.1±0.7 to 8.6±0.6 mg/dL) from 24 to 96h after treatment. Plasma magnesium decreased from a baseline level of 2.1±0.1 mg/dL to a plateau level of 1.8±0.1 mg/dL, which was sustained from 24 to 48h after treatment. The present study provides evidence of the absorption of exogenous 1,25(OH)2D3 from the bovine vaginal wall, as shown by the marked elevation of plasma 1,25(OH)2D3 levels by 2h after administration, and indicates the possible utility of intravaginal administration of 1,25(OH)2D3 for prophylaxis of hypocalcemia.

Possible direct induction by estrogen of calcitonin secretion from ultimobranchial cells in the goldfish

The plasma level of calcitonin (CT), a calcium (Ca)-regulating hormone, is known to increase in female teleosts during the reproductive period. In the present study, a correlation between plasma CT and Ca and one between plasma CT and the gonad somatic index were demonstrated in the female goldfish but not in the male. To clarify the relationship between CT and Ca, we examined the plasma CT and Ca levels after injecting immature goldfish with estrogen. At day 1, the plasma CT level significantly increased, whereas the plasma Ca level was not changed from its initial level. This result suggests that the trigger of CT secretion is estrogen and that estrogen directly acts on the ultimobranchial gland (UBG), a CT-secreting organ. To determine whether the UBG is equipped with estrogen receptor (ER), an ER binding assay and immunohistochemical staining of UBG cells with an antibody against ER were conducted. As a result, estrogen-specific binding ( K d, 18.52 nM; B max, 1.35 pmol/mg protein) and ER-immunoreactivity in the UBG were demonstrated. Furthermore, the expression of α,β, and γ types of ER in the UBG was also detected by use of the reverse-transcription polymerase chain reaction. Thus, we concluded that estrogen acts on the UBG to induce the release of CT, which in turn plays an important role in reproduction directly and/or indirectly through Ca. This is the first report on the existence of ERs in a teleost UBG and the occurrence of CT secretion caused by estrogen.

The stress axis, stanniocalcin, and ion balance in rainbow trout

In teleosts, the stress hormone cortisol and the calcium regulatory hormone stanniocalcin (STC) are both involved in the regulation of ion balance. Under stressful conditions, ion balance is easily disturbed as stressors via the stress signals they evoke disturb easily and primarily gill function. The gills are key in fish gas exchange and ion regulation. The present work evaluates the effect of the pivotal stress signal cortisol, the eventual output of the stress axis on STC secretion in freshwater rainbow trout ( Oncorhynchus mykiss). Plasma cortisol levels were manipulated by intraperitoneal injections of porcine ACTH 1–39 or dexamethasone (Dex), and plasma cortisol, STC and mineral status were assessed. A perifusion assay of trout Stannius corpuscles was validated and used to study the direct effects of stress-related signals on STC release. In perifusion, cortisol, adrenocorticotropic hormone (ACTH), and dexamethasone did not affect STC release. ACTH injections increase plasma cortisol (corresponding to an acute stress) and STC concentrations, but did not affect mineral status. Dexamethasone injections resulted either in a classical hypocortisolinemia or, unexpectedly, in hypercortisolinemia. However, independently of the resulting cortisol status Dex induced a chronic stress effect, as indicated by decreased plasma Na, Cl, and Ca levels, and increased plasma STC concentrations. The increased STC secretion cannot be explained by the classical elevation of plasma calcium concentration. Thus, plasma parameters other than calcium could be involved and we propose that STC secretion might be stimulated also by a decrease of NaCl concentrations, implying a broader function than the classical hypocalcemic action of STC.

Blood pressure and α-vascular reactivity in hypertensive rats treated with amlodipine and dietary Ca

It has been suggested that the combination of dietary Ca and Ca 2+ channel antagonists could have a synergic antihypertensive effect. In this study, 3-week-old male spontaneously hypertensive rats (SHR) were randomized into four groups of animals. Two of these groups were fed on a normal Ca diet (Ca 1%) and the other two groups were fed on a Ca-enriched diet (Ca 2.5%). One of the groups fed on each diet also received amlodipine (1 mg/kg/day) in their drinking water. Systolic and diastolic arterial blood pressure were measured weekly in the rats, from the 6th week of life until the 25th week of life, by the tail-cuff method, and we also calculated the corresponding pulse pressure values (systolic blood pressure−diastolic blood pressure). Determination of plasma Ca levels by colourimetric methods, and measurement in pithed rats of the pressor responses to the α-adrenoceptor agonists methoxamine and B-HT 920 (5-allyl-2-amino-5,6,7,8-tetrahydro-4 H-thiazolo-(4,5- d)-acepin-dihydrochloride, talixepole) were also performed using 16- and 23-week-old animals from the different groups. The Ca-enriched diet decreased systolic and diastolic blood pressure in SHR. Almodipine also decreased systolic and diastolic blood pressure in SHR, and this drug intensified the antihypertensive effect of the Ca 2.5% diet in the SHR between weeks 13 and 18. Nevertheless, in the 19- to 25-week-old SHR amlodipine antagonized the effect of dietary Ca on arterial blood pressure. A decrease in the pulse pressure was seen only in the 15- to 20-week-old SHR which had been simultaneously treated with dietary Ca and amlodipine. All the treatments used increased calcaemia, and the highest plasma Ca levels were obtained in the animals which had received the combined treatment with Ca and amlodipine. The responses to methoxamine and to B-HT 920 in the pithed 16-week-old SHR were similar in the four groups of animals. The responses to these agonists in the pithed 23-week-old SHR fed on the Ca-enriched diet were smaller than the corresponding responses in 23-week-old SHR of the untreated group. By contrast, the responses to these agonists were slightly higher in the pithed 23-week-old SHR which were treated with amlodipine than in the pithed 23-week-old SHR in the untreated group. Moreover, amlodipine partially reversed the effect of dietary Ca on α-vascular reactivity. According to our results, it would seem inadvisable to use dietary Ca with a Ca 2+ channel antagonist with the aim of controlling arterial blood pressure.

Effects of dietary cadmium on calcium homeostasis, Ca mobilization and bone deformities in Atlantic salmon (Salmo salarL.) parr

Atlantic salmon parr were reared for 4 months on experimental fish-meal-based diets supplemented with 0 (control), 0.5, 5, 25, 125 or 250 mg Cd kg−1 feed to assess the effects of dietary Cd on active Ca uptake, mobilization of Ca from internal reservoirs, and development of bone malformations. The accumulation of dietary Cd in tissues was, in decreasing order, intestine > kidney >> gill > bone. No significant accumulation of Cd in the scales was observed. Strongest inhibition of ATP dependent Ca uptake (measured as Ca2+- and Na+/K+-ATPase) was observed in the intestine of salmon fed 25 mg Cd kg−1. This suppression in active intestinal Ca uptake did not lead to disturbed plasma Ca levels. Significant reduction of Ca from the scales in salmon fed 25 mg Cd kg−1, indicates remobilization of Ca to maintain Ca homeostasis. At the end of the experiment no significant differences were observed in bone Ca levels, nor were any bone malformations observed in any of the dietary Cd-exposed salmon. This indicates that bone as an endogenous Ca reservoir is spared compared with scales. It was concluded that dietary Cd-induced disturbance of Ca homeostasis did not lead to bone deformities, even when Atlantic salmon were fed high amounts of cadmium. This indicates a low risk of spinal deformations being developed in Atlantic salmon sub-chronically exposed to high Cd concentrations in the feed.

Dynamics of plasma Ca and calcitonin levels in stonefish (Inimicus japonicus) administered a high-Ca solution into the stomach.

In stonefish, changes in plasma total Ca and calcitonin levels were examined after administration of a high-Ca solution into the stomach. Blood was taken successively at 0, 1, 3, 9, 33, and 81 hr from a fine tube cannulated into the aortic bulb. Plasma Ca levels increased acutely at 1 hr and attained the peak after 3-9 hr of the administration. Although plasma calcitonin levels did not exhibit conspicuous changes for 1-3 hr, they began to rise significantly at 33 hr. The plasma Ca level began to decline significantly at 33 hr, although the level was still significantly higher than the initial level. At 33 hr, however, the plasma calcitonin level still continued to increase. At 81 hr, the plasma Ca level had returned to the initial level. At that time, the plasma calcitonin level was also significantly lower than that at 33 hr. These results suggest that, in stonefish, the ultimobranchial gland has the ability to respond physiologically to rises in plasma Ca levels, to secrete calcitonin, and to cease the secretion when the plasma Ca levels return to the initial level.

Vitamin D Receptor (VDR) Knockout Mice Reveal VDR-Independent Regulation of Intestinal Calcium Absorption and ECaC2 and Calbindin D9k mRNA

To study the role of calbindin D(9k) (CaBP) and epithelial calcium channel ECaC2 in intestinal calcium (Ca) absorption, vitamin D receptor knockout (KO) and wild-type (WT) mice were fed either 0.5% Ca or a 2.0% Ca rescue diet starting at 21 d of age. Ca absorption and parameters involved in this process were measured at 60 or 90 d of age. Compared with WT, KO mice fed the 0.5% Ca diet had higher plasma parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], and lower plasma Ca and insulin-like growth factor-I (IGF-I). Duodenal Ca absorption (% Ca absorbed) in KO mice was reduced 71% relative to WT mice and was associated with 55% lower CaBP mRNA, 47% lower CaBP protein and 95% lower ECaC2 mRNA levels. Compared with WT mice, the percentage of Ca absorbed in KO mice fed the 0.5% Ca diet was inappropriately low for the level of duodenal CaBP. The 2% Ca rescue diet normalized plasma Ca, prevented osteomalacia, increased growth and plasma IGF-I levels, but did not normalize plasma PTH or 1,25(OH)(2)D(3) in KO mice. In addition, the relationship between CaBP protein and the percentage of Ca absorbed was normalized, whereas ECaC2 mRNA fell to near zero. Our data demonstrate that higher CaBP levels do not ensure high rates of duodenal Ca absorption and that transcellular Ca absorption can occur even when ECaC2 gene expression is very low. In addition, our data suggest that the 2% Ca diet promotes a vitamin D receptor-independent anabolic effect on bone formation and calcium absorption, leading to improved calcium balance even in the presence of high PTH levels.

Estimation of Bioavailability of Salmon Calcitonin from the Hypocalcemic Effect in Rats (I): Pharmacokinetic-Pharmacodynamic Modeling Based on the Endogenous Ca Regulatory System

The hypocalcemic effect of salmon calcitonin (sCT) after intravenous administration was explained on the basis of an integrated pharmacokinetic-pharmacodynamic (PK-PD) model with the endogenous Ca regulatory system in the rat. The pharmacokinetics of sCT described by a conventional two-compartment model showed the extremely rapid elimination of sCT from plasma (MRT; 6.86 min). The hypocalcemic effect of sCT reached a peak from 0.5 to 1.5 hrs after administration, and the peak time tended to prolong with increasing doses. This delay in pharmacological effect of sCT against plasma concentration may be a result of a summation of multiple actions of the endogenous Ca regulatory system including feedback control. The plasma Ca regulation system in the rat was investigated by i.v. bolus administration of calcium gluconate and/or endogenous (rat) calcitonin (rCT). Since non-linearity in the relationship between Ca and rCT concentrations in plasma was observed, we assumed that rCT was secreted in accordance with the plasma Ca level via an exponential function. The pharmacokinetics of rCT was represented as a linear one-compartment model. To link the rCT level with plasma Ca level, an additional effect compartment was required to explain the delay in onset and decline of the pharmacological effect. This Ca regulation model explained the observed Ca and rCT profiles in plasma after administration of Ca and/or rCT. The plasma Ca levels after administration of sCT could be well described by the present integrated model. This suggested the potential for prediction of plasma sCT concentration only from the hypocalcemic effect after extravascular administration of sCT, using this PK-PD model.

Direct raises in blood Ca levels by infusing a high-Ca solution into the blood stream accelerate the secretion of calcitonin from the ultimobranchial gland in eels.

In eels, a CaCl(2) solution was infused into the pneumatic duct vein. Plasma Ca levels were significantly increased during 3 hr and were followed by significant raises in plasma calcitonin levels. These results strongly suggest that, in eels, direct raises in blood Ca levels by infusion of a high-Ca solution via blood vessels can accelerate the secretion of calcitonin from the ultimobranchial gland.

Ultimobranchial Glands in the Teleost (Plecoglossus altivelis ryukyuensis): Special References to Changes of Gland Volume with Maturation

In lower vertebrates, the bone-mineralizing hormone "calcitonin" is secreted from ultimobranchial glands, which assume various shapes, e.g., follicles, cellular masses, or cell strands. Histological observations support the view that in some teleosts, the glands increase in size when females maturate. We determined the exact volume of the gland in juveniles and adult males and females of a teleost, Ryukyuayu (Plecoglossus altivelis ryukyuensis). Furthermore, we examined plasma Ca, Na and K levels. In this species, the gland was fundamentally composed of a single follicle. The gland volume was converted to numerical data under a certain condition. It thus became clear that the value of the follicle wall was significantly increased only in maturing and mature females with high plasma Ca levels and that the value of the lumen did not show any statistically significant changes during growth and maturation.

1,25(OH) 2D 3 only affects long-term levels of plasma Ca 2+ but not the rapid minute-to-minute plasma Ca 2+ homeostasis in the rat

Results from our lab have shown previously that parathyroid hormone (PTH) is not the key factor in the rapid regulation of plasma Ca 2+. The possible role of 1,25(OH) 2D 3 in the rapid minute-to-minute regulation of plasma Ca 2+, as addressed by a possible rapid non-genomic action of 1,25(OH) 2D 3, was therefore studied in vivo in rats. The rapid calcemic recovery from induction of hypocalcemia by a brief EGTA infusion was examined in vitamin D-depleted rats with intact parathyroid glands and in vitamin D depleted rats 1 h after parathyroidectomy (PTX). The influence of different levels of plasma 1,25(OH) 2D 3 on the rapid calcemic recovery from hypocalcemia was examined in PTX rats treated with 1,25(OH) 2D 3 for two days at two different doses of 0.2 μg/day, 0.05 μg/day or vehicle, and in PTX rats being BNX for two days, as well. Additionally, the long-term effect of 1,25(OH) 2D 3 on plasma Ca 2+ homeostasis was examined. Plasma Ca 2+ recovered significantly ( P < 0.05) 10 min after discontinuing EGTA in vitamin D-depleted rats with or without parathyroid glands. Plasma Ca 2+ increased significantly ( P < 0.05) and at the same rate after induction of hypocalcemia in PTX rats with different levels of plasma 1,25(OH) 2D 3. The final levels of plasma Ca 2+ obtained were set by 1,25(OH) 2D 3 in a dose-related manner. 1,25(OH) 2D 3 did not affect the rapid calcemic recovery from EGTA induced hypocalcemia, but only had an effect on the long-term plasma Ca 2+ homeostasis in the rat.

High Serum and Cerebrospinal Fluid Ca/Mg Ratio in Recently Hospitalized Acutely Depressed Patients

Calcium (Ca) and magnesium (Mg) are involved in many processes related to depression. Evaluations of serum and plasma Ca and Mg levels in depressive disorders do not show consistent results. The few studies that examined their cerebrospinal fluid (CSF) levels tended to find no differences between depressed patients and controls. Because both hypercalcemia and hypomagnesemia are associated with depression, and as Mg may function as a Ca antagonist, it is suggested that the relationship between these cations could be different in depressed patients and controls. We examined CSF and serum Ca and Mg in acutely depressed patients diagnosed as having major depressive disorder or being in a depressive episode of bipolar disorder. Controls were subjects undergoing lumbar puncture as part of an evaluation for headache or suspected meningitis and found to demonstrate no physical or mental disorder. Serum and CSF Ca/Mg ratios were found to be elevated in the depressed patients compared with the controls. A retrospective analysis of previous trials assessing serum/plasma or CSF Ca and Mg does not seem to refute the findings of this study. We further discuss our findings in their relation to the acuteness of the depressive disorders.

Vitamin K2 (menatetrenone) treatment increased bone strength in rats given low-calcium diets

Two experiments were carried out in 4-week-old rats. First, the effect of dietary calcium (Ca) content (0.05, 0.1, 0.2, 0.5 and 1.16%) on bone loss was assessed for 3 weeks. Dry weight of the femur showed a Ca-content-dependent decrease. Significant decrease in body weight and plasma Ca level was observed in the 0.05 and 0.1% Ca diet groups, but not in other groups. Second, the curative effect of V.K2 on bone strength was examined. After being fed a 0.2%-Ca diet for 3 weeks, rats were fed 0.2%- or 0.5%-Ca diets for the next 6 weeks with or without V.K2 treatment. At the beginning and after 3 and 6 weeks of treatment, femurs and lumbar vertebra (L3) were collected. In the 0.2%-Ca group, bone mineral density (BMD) and bone strength in the femur gradually increased, but were much lower than those in the intact group. In the 0.5%-Ca group, both parameters in the femur and L3 were rapidly increased. V.K2 treatment did not affect the BMD or bone strength in the femur at either point. However, the bone strength in L3 in the V.K2 group was higher than that in the 0.5%-Ca group at 3 weeks and in the 0.2%-Ca group at 6 weeks than that in the respective control group. These findings suggest that V.K2 has curative effect on bone strength in the vertebra.

Dietary calcium modulates Mycobacterium paratuberculosis infection in beige mice

A 6-month study was conducted to evaluate the effects of feeding different levels of dietary calcium (Ca) on the persistence of Mycobacterium paratuberculosis infection using a mouse model. Beige mice, averaging 8 weeks of age, were randomly assigned to one of the following dietary treatments: 1) 0.02% Ca, 2) 0.15% Ca, 3) 0.45% Ca, and 4) 1.0% Ca. Mice were infected intraperitoneally with 10 8 CFU viable M. paratuberculosis for 1, 3, and 6 month periods. Plasma Ca levels was unaffected by dietary Ca ( x = 7.3 mg/dl). Plasma levels of 1,25(OH) 2D 3 was elevated significantly in 0.02% and 0.15% Ca groups compared to other treatments at the end of each period, with the highest levels observed for 0.02% Ca mice and intermediate values for 0.15% Ca mice. One month after infection, numbers of viable M. paratuberculosis cultured from the spleen were significantly reduced for 0.15% Ca mice, whereas the number of bacteria isolated from the liver and mesenteric lymph node (MLN) were higher for the 0.02% Ca group. There were no differences in bacterial numbers in the ileum although they tended to be higher for the 0.02% Ca group. Three months after infection, bacterial numbers in the spleen, ileum, and MLN did not differ across treatments, however, significantly lower numbers were found in the liver of 1.0% Ca mice. Reduced bacterial counts were also observed in the liver of 0.15%, 0.45%, and 1.0% Ca mice after a 6-month infection period compared to the 0.02% Ca group, with the lowest numbers isolated from the 1.0% Ca mice. Numbers of viable bacteria cultured from the ileum and MLN after 6 months of infection were also significantly reduced in 1.0% Ca mice. These results suggest that Ca metabolism is an important modulator of M. paratuberculosis infection.

Dry Matter Intake and Plasma Mineral Levels of Steers Consuming Broiler Litter Containing Aluminum Sulfate

Aluminum sulfate applied to litter in broiler houses has been shown to lower soluble P in the runoff when the litter is applied to land. Because broiler litter is also used as a cattle feed, two trials using a total of 63 steers were conducted to determine whether treating broiler litter with aluminum sulfate affected consumption of a corn-litter mixture and plasma Al, Ca, Mg, and P levels. Treatments were pasture only or pasture plus ground corn (Zea mays L.) mixed (1:1; as-fed) with either broiler litter treated with aluminum sulfate or untreated litter. In both trials, DM intake was lower (P<0.05) for the cornlitter mixture containing aluminum sulfate than with the mixture containing untreated litter. Plasma Al, Ca, and Mg levels were not affected (P>0.10) by treatments. In trial 1, plasma P was lower (P<0.05) in steers receiving litter treated with aluminum sulfate than in steers receiving untreated litter, but higher than in steers on pasture only. In trial 2, plasma P was not affected (P>0.10) by treatment. No visible signs of disease were observed in steers receiving aluminum sulfate-treated litter. Aluminum sulfate treatment of litter lowered DM intake of a corn-litter mixture fed to steers on bermudagrass.

Phosphate Transport in Pig Proximal Small Intestines during Postnatal Development: Lack of Modulation by Calcitriol

The role of calcitriol in the intestinal absorption of inorganic phosphate (Pi) during postnatal development was studied in newborn [<1 week postpartum (pp)], suckling (3–4 weeks pp), and weaned (>6 weeks pp) control piglets (con) and piglets suffering from inherited calcitriol deficiency (def). In addition, a number of def piglets were treated with vitamin D3 (def-D3). Regardless of age, plasma calcitriol concentrations in def piglets were unphysiologically low (16–21 pg/ml) and differed significantly from those in respective con animals (60–69 pg/ml) and vitamin D3-treated def piglets (50–56 pg/ml). However, newborn and suckling def piglets had normal Ca (∼3.0 mmol/liter) and Pi (∼2.8 mmol/liter) plasma levels. Def piglets became hypocalcemic (1.9 mmol/liter) and hypophosphatemic (1.9 mmol/liter) between 4–6 weeks pp. Treatment with vitamin D3 significantly increased plasma Ca (3.2 mmol/liter) and Pi (2.7 mmol/liter) levels in weaned def animals. Regardless of calcitriol status, net Pi flux rates (active Pi absorption, as determined with the in vitro Ussing-chamber technique) from the upper small intestines was maximal at birth [170–224 nmol/(cm2·h)] and decreased by approximately 80% during the first week of life before remaining constant [30–50 nmol/(cm2·h)] during the following development. In weaned def piglets, net Pi flux rates were significantly lower by about 80% compared with those in con animals. Treatment of def piglets with vitamin D3 had no effect in newborn and suckling animals but reconstituted net Pi flux rates to normal values at weaning age. Age-dependent and calcitriol-mediated changes in net Pi flux rates were paralleled by respective maximum velocity values of Na+-dependent Pi uptake across the brush border membrane of the enterocytes (newborn piglets, 1.9–2.2 nmol/(mg protein·10 sec); suckling piglets, 0.4–0.6 nmol/(mg protein·10 sec); weaned piglets, 0.7, 0.3, and 0.7 nmol/(mg protein·10 sec) in con, def, and def-D3 animals, respectively). These findings suggest that the apical Pi uptake represents the major rate-limiting step of the overall transepithelial Pi transport. At weaning, Na+/Pi transport across the intestinal brush-border membrane is clearly stimulated by calcitriol, but no significant effects of age or calcitriol on the Km values (0.5–0.7 mmol/liter) were observed. In conclusion, our findings reveal calcitriol-independent mechanisms for active intestinal Pi absorption during the neonatal and suckling periods. The onset of the classical calcitriol-dependent mechanism for active intestinal Pi absorption does not occur until weaning.

Phosphate transport in pig proximal small intestines during postnatal development: lack of modulation by calcitriol.

The role of calcitriol in the intestinal absorption of inorganic phosphate (Pi) during postnatal development was studied in newborn [<1 week postpartum (pp)], suckling (3-4 weeks pp), and weaned (>6 weeks pp) control piglets (con) and piglets suffering from inherited calcitriol deficiency (def). In addition, a number of def piglets were treated with vitamin D3 (def-D3). Regardless of age, plasma calcitriol concentrations in def piglets were unphysiologically low (16-21 pg/ml) and differed significantly from those in respective con animals (60-69 pg/ml) and vitamin D3-treated def piglets (50-56 pg/ml). However, newborn and suckling def piglets had normal Ca (approximately 3.0 mmol/liter) and Pi (approximately 2.8 mmol/liter) plasma levels. Def piglets became hypocalcemic (1.9 mmol/liter) and hypophosphatemic (1.9 mmol/liter) between 4-6 weeks pp. Treatment with vitamin D3 significantly increased plasma Ca (3.2 mmol/liter) and Pi (2.7 mmol/liter) levels in weaned def animals. Regardless of calcitriol status, net Pi flux rates (active Pi absorption, as determined with the in vitro Ussing-chamber technique) from the upper small intestines was maximal at birth [170-224 nmol/(cm2 x h)] and decreased by approximately 80% during the first week of life before remaining constant [30-50 nmol/(cm2 x h)] during the following development. In weaned def piglets, net Pi flux rates were significantly lower by about 80% compared with those in con animals. Treatment of def piglets with vitamin D3 had no effect in newborn and suckling animals but reconstituted net Pi flux rates to normal values at weaning age. Age-dependent and calcitriol-mediated changes in net Pi flux rates were paralleled by respective maximum velocity values of Na+-dependent Pi uptake across the brush border membrane of the enterocytes (newborn piglets, 1.9-2.2 nmol/(mg protein 10 sec); suckling piglets, 0.4-0.6 nmol/(mg protein x 10 sec); weaned piglets, 0.7, 0.3, and 0.7 nmol/(mg protein x 10 sec) in con, def, and def-D3 animals, respectively). These findings suggest that the apical Pi uptake represents the major rate-limiting step of the overall transepithelial Pi transport. At weaning, Na+/Pi transport across the intestinal brush-border membrane is clearly stimulated by calcitriol, but no significant effects of age or calcitriol on the Km values (0.5-0.7 mmol/liter) were observed. In conclusion, our findings reveal calcitriol-independent mechanisms for active intestinal Pi absorption during the neonatal and suckling periods. The onset of the classical calcitriol-dependent mechanism for active intestinal Pi absorption does not occur until weaning.