Relationship of intestinal and plasma calcium-binding protein to intestinal calcium absorption.
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Animals↗
Biomedical subjects
A Bar
Publications and source records attributed to A Bar.
Synthesis and biological action of 3-deoxy-vitamin D3 and 3-deoxy-25-hydroxyvitamin D3.
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Animals↗
The interaction between dietary calcium and gonadal hormones in their effect on plasma calcium, bone, 25-hydroxycholecalciferol-1-hydroxylase, and duodenal calcium-binding protein, measured by a radioimmunoassay in chicks.
Male chicks, fed low, normal, or high calcium- and cholecalciferol-containing diets for 14 days, were given three combined injections of 17 beta-estradiol and testosterone (7 and 2.4 mg/kg/dose, respectively) or the vehicle alone, at 3-day intervals. The hormonal treatment resulted in increased plasma calcium and medullary bone calcium concentrations, independently of the dietary calcium intake. Kidney 25-hydroxycholecalciferol-1-hydroxylase and duodenal calcium-binding protein were increased in response to gonadal hormones. The magnitude of this response markedly diminished with increased calcium intake and almost completely disappeared in chicks fed the high calcium diet. The results suggest that the increases in plasma calcium and medullary bone formation due to gonadal hormones are independent of calcium intake while the effect of hormones on duodenal calcium-binding protein and the 25-hydroxycholecalciferol-1-hydroxylase activity appears to be mediated through the change in calcium needs due to medullary bone formation.
25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
Gait consistency test based on the impulse-momentum theorem.
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Biomechanical Phenomena↗
Involvement of cholecalciferol metabolism in birds in the adaptation of calcium absorption to the needs during reproduction.
1. The metabolism of calcium and cholecalciferol in quail (Coturnix coturnix japonica) and chicken (Gallus domesticus) during maturation was correlated to gonadal activity and plasma oestrogen levels. 2. Birds with undeveloped ovaries (immature), developed ovaries but not laying (mature), and after laying 3-8 eggs (laying), were used in the first series. 3. Birds in which egg production had been arrested by Nicarbazin, were used in the second series. 4. Plasma 17 beta-oestradiol and calcium were elevated in the mature bird, with no further change in the laying bird. Kidney 25-hydroxycholecalciferol-1-hydroxylase and intestinal calcium-binding protein increased slightly in the mature bird, whereas they were grossly elevated in the laying bird. 5. Calcium and phosphorus absorption were markedly elevated in the laying bird. 6. No changes were noted in plasma 25-hydroxycholecalciferol, at any stage of maturation. 7. During the arrest of egg production by Nicarbazin, 17 beta-oestradiol level, calcium concentration of plasma, and medullary bone were maintained. Kidney 25-hydroxy-cholecalciferol-1-hydroxylase, intestinal calcium-binding protein and absorption of calcium were strikingly reduced. 8. The results suggest that changes in calcium absorption and cholecalciferol metabolism during maturation in birds are not directly affected by gonadal hormones; they appear to represent an adaptation to the increased calcium needs due to medullary bone formation and, more importantly, to the large losses of calcium imposed by shell formation.
Adaptation, Physiological↗
Differential response of calcium transport systems in laying hens to exogenous and endogenous changes in vitamin D status.
Changes in intestinal calcium absorption, calcium deposition into egg shell, and intestinal, renal and uterine calcium-binding protein (CaBP) in laying hens were related to changes in 25 hydroxycholecalciferol-1-hydroxylase activity (1-hydroxylase), or to the supplementation of 1alpha-hydroxycholecalciferol (1alpha-OH-CC). The onset of egg production resulted in an increased kidney 1-hydroxylase activity and intestinal and uterine CaBP. Renal concentrations of CaBP remained unchanged. Intestinal calcium and phosphorus absorption, during the period of egg shell formation, and duodenal calcium-binding protein (CaBP), were higher in 1alpha-OH-CC-fed than in cholecalciferol-fed hens. Renal or uterine CaBP and calcium deposition into the egg shell did not fluctuate with the vitamin D source or concentration. 1alpha-OH-CC injection into non-laying Nicarbazinfed hens resulted in an increase in intestinal but not renal or uterine CaBP concentrations. It is suggested that (a) CaBP in various organs responded independently to the same stimuli; and (b) calcium deposition into egg shell and uterine CaBP level are not related to kidney 1-hydroxylase activity or concentration of 1,25 dihydroxycholecalciferol.
25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
Phosphate absorption and excretion in the young turkey, as influenced by calcium intake.
Phosphorus absorption in the young turkey, measured with the aid of yttrium-91 as a reference substance, was linear with phosphorus intake. This observation suggested the lack of adaptation of the phosphorus transport mechanism to changes in the phosphorus needs. Phosphorus retention and bone ash initially increased with increased intake to plateau at a dietary phosphorus concentration of about 0.8%. The excess phosphorus absorbed from diets higher in phosphate, was eliminated in the urine. Plasma inorganic phosphate was linear with absorbed phosphate. The apparent phosphorus absorption from the basal vegetable diet was 45% of the intake and that of the inorganic supplement, sodium phosphate and calcium monophosphate, was about 100%, at low calcium intakes. Increasing the calcium intake above 440 mg/day progressively depressed the absorption of phosphate. This inhibitory action of calcium on phosphate absorption was resolved into a linear coefficient.
Animals↗
Calcium-binding protein and kidney 25-hydroxycholecalciferol-1-hydroxylase activity in turkey poults.
A vitamin D-dependent calcium-binding protein (CaBP) has been found in the intestinal mucosa of turkeys (Meleagris gallopavo). This protein is similar, if not identical, to the corresponding one found in the intestine of the chicken (Gallus domesticus). The concentration of intestinal CaBP in the intestine of cholecalciferol-fed turkey poults was twice that found in the intestine of the domestic chicken of parallel age. Dietary calcium or phosphorus restriction resulted in a significant increase in intestinal CaBP. This increase was less pronounced than that obtained in chickens. The relationship between duodenal CaBP and dietary calcium appears to be linear. Cholecalciferol (vitamin D) deficiency or dietary calcium, but not phosphorus, restriction resulted in an increase of kidney 25 hydroxycholecalciferol-1-hydroxylase activity in vitro. The values of activity obtained in turkeys were higher than those obtained under the same experimental conditions in chicks. Bone ash was reduced by dietary calcium, phosphorus or cholecalciferol restriction. Plasma inorganic phosphorus was lower in either cholecalciferol- or phosphorus-restricted turkeys. Plasma calcium was significantly higher in the phosphorus-restricted turkeys than in the calcium-restricted or control turkeys.
25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
Use of 1alpha-hydroxycholecalciferol in the prevention of bovine parturient paresis.
A synthetic biologically active derivative of vitamin D (350 microgram of 1alpha-hydroxycholecalciferol [1alpha(OH)CC]) was injected into 2 nonlactating 7-year-old Israeli-Friesian cows. Plasma calcium values increased after 24 hours, peaked at 48 hours, and returned to base-line values 120 hours after injection. An injection of 350 microgram of 1alpha(OH)CC was given to 23 parturient-paresis-prone Israeli-Friesian cows from 7 days to 6 hours prepartum; 13 cows were injected once, 6 were injected twice, and 4 were injected 3 times, all at 48-hour intervals. Parturient-paresis-prone cows (n = 23) of the same breed were used as controls. Within 0 to 36 hours postpartum, plasma calcium concentrations were found to be higher in cows injected with 1alpha(OH)CC than in the control cows. The increase was highly significant (P less than 0.01) in cows injected at least twice. None of the cows injected with 1alpha(OH)CC, within 72 to 24 hours prior to calving developed parturient paresis; but 9 of 23 control cows developed parturient paresis. Prior to calving, none of the injected cows developed hypercalcemia and there was no local or systemic clinically detectable signs of toxiosis. When given at the right time prepartum, 1alpha(OH)CC is considered to be an improvement over previous methods of preventing bovine parturient paresis.
Animals↗
Regulation of intestinal calcium absorption in the laying quail: independent of kidney vitamin D hydroxylation.
Two experiments were carried out with laying quail (Coturnix coturnix japonica) fed either cholecalciferol (40 mug/kg) or 1 alpha-hydroxycholecalciferol (8 mug/kg). Recovery following vitamin D depletion, as indicated by egg production and shell deposition, was faster in quail fed 1 alpha-hydroxycholecalciferol than in those fed cholecalciferol. Overall intestinal calcium absorption was higher in the 1 alpha-hydroxycholecalciferol-fed quail due to a higher absorption in the middle parts of the small intestine. This was associated with corresponding differences in the concentration of calcium binding protein. Intestinal calcium absorption was markedly higher during periods of shell formation than during periods of uterine inactivity in quail fed either cholecalciferol or 1 alpha-hydroxycholecalciferol. It is suggested, therefore, that the mechanism responsible for this difference is independent of vitamin D hydroxylation in the kidney.
Animals↗
The purification of calcium-binding protein from the uterus of the laying hen.
Calcium-binding proteins from the chick intestine and uterus of the laying hen (Gallus domesticus) were isolated and purified by identical methods. Proteins from each source were shown to exhibit identical electrophoretic mobility and were immunologically identical. Estimation of molecular size by gel filtration indicated a value of approximately 28,000 daltons for both the chick intestinal and hen uterine calcium-binding proteins. The amino acid compositions of chick intestinal and hen uterine calcium-binding proteins were essentially identical.
Amino Acids↗
Calcium-binding protein and calcium absorption in the laying quail (Coturnix coturnix japonica).
A vitamin D3-dependent calcium-binding protein (CaBP) has been found in the intestinal mucosa of Japanese quail (Coturnix coturnix japonica). This protein is similar, if not identical to that of the chick (Gallus domesticus). A similar protein fraction appears also in uterine mucosa of laying quail. Both intestinal and uterine CaBP levels are higher in laying than in non-laying quails. Uterine CaBP was higher during egg shell formation than during uterine inactivity. The slight corresponding difference in the intestinal CaBP was not significant. Intestinal calcium absorption measured with 91Y as a reference substance was higher in birds during formation of egg shell than in those with inactive uteri. The possible role of CaBP in calcium translocation is discussed.
Animals↗
Response of renal calcium-binding protein. Independence of kidney vitamin D hydroxylation.
Dietary calcium and dietary phosphorus restriction were studied in chicks fed either cholecalciferol or 1alpha-hydroxycholecalciferol. Intestinal calcium absorption and calcium-binding protein of 1alpha-hydroxycholecalciferol-treated chicks remained unchanged under dietary calcium restriction, but increased under dietary phosphorus restriction. Kidney calcium-binding protein was not altered by dietary caclium restriction in chidks treated with either cholecalciferol or 1alpha-hydroxycholecalciferol, but increased under dietary phosphorus restriction independent of the vitamin D source. In contrast to the intestine, calcium-binding activity of the kidney was found to be poorly related to the calcium-binding protein concentration. It is suggested that kidney calcium-binding protein is regulated by a mechanism different from that of intestinal calcium-binding protein, and that its concentration in renal tissue is related to renal caclium excretion or plasma calcium level.
Animals↗
The functional metabolism of vitamin D in chicks fed low-calcium and low-phosphorus diets.
Radioactively labelled cholecalciferol was administered continuously to chicks that were fed normal, low-calcium and low-phosphorus diets. It has been possible to show that under such steady state conditions with regard to cholecalciferol, and mineral restriction, the animal reacts by increased accumulation of 1, 25-dihydroxycholecalciferol in the intestinal and the kidney cell, which was associated in the intestine with an increased calcium-binding activity. A similar accumulation of 1, 25-dihydroxycholecalciferol in bone was not noticed. It is proposed that the intestine and the kidney, but not bone, are the main target organs for cholecalciferol in the maintenance of calcium homeostasis, and that both calcium and phosphorus play a role in the regulation of the formation and subsequent function of 1, 25-dihydroxycholecalciferol.
Animals↗