ROLE OF THE PARATHYROID GLANDS IN THE ENHANCEMENT OF INTESTINAL CALCIUM ABSORPTION IN RESPONSE TO A LOW CALCIUM DIET

1977 ◽  
Vol 74 (3) ◽  
pp. 345-354 ◽  
Author(s):  
J. FOX ◽  
R. SWAMINATHAN ◽  
T. M. MURRAY ◽  
A. D. CARE
Keyword(s):  
Small Intestine ◽  
Calcium Binding ◽  
Calcium Absorption ◽  
Binding Protein ◽  
Calcium Binding Protein ◽  
Intestinal Calcium Absorption ◽  
Parathyroid Glands ◽  
Calcium Diet ◽  
Low Calcium Diet ◽  
Low Calcium

SUMMARY The phenomenon of adaptation of intestinal calcium absorption to changes in dietary calcium has been studied in conscious pigs with Thiry–Vella jejunal loops. The result of decreasing the calcium content of the diet from 1·2 to 0·1% was an increase in the efficiency of the net absorption of calcium from the fluid used to perfuse the jejunal loop; this increase took place 4–6 days after the change in diet. A similar effect was noted in four pigs which had previously been parathyroidectomized and in two thyroparathyroidectomized pigs with thyroxine replacement therapy. The effect seen in the parathyroidectomized animals was not attributable to an increase in the concentration gradient of calcium ions between the jejunal lumen and the blood after the change to the low calcium diet. There was a marked increase in the amount of calcium-binding protein in the mucosa taken from the distal three-quarters of the small intestine of intact pigs fed a low calcium diet. However, after parathyroidectomy, the level of calcium in the diet had no significant effect on the amount of calcium-binding protein in the small intestine. It is concluded that, in pigs, neither parathyroid hormone nor calcitonin is necessary for intestinal adaptation to a low calcium diet and that, although this adaptation may be mediated by 1,25-dihydroxycholecalciferol, a significant increase in the level of calcium-binding protein in the intestine is only seen when the parathyroid glands are intact.

Radioimmunoassay Studies of Intestinal Calcium-binding Protein in the Pig. I. Identification of Intestinal Calcium-binding Protein in Blood and Response to a Low Calcium Diet

1975 ◽  
Vol 53 (6) ◽  
pp. 1129-1134 ◽  
Author(s):  
B. M. Arnold ◽  
M. Kuttner ◽  
R. Swaminathan ◽  
A. D. Care ◽  
A. J. W. Hitchman ◽  
...  
Keyword(s):  
Small Intestine ◽  
Intestinal Mucosa ◽  
Calcium Binding ◽  
Binding Protein ◽  
Calcium Binding Protein ◽  
Intestinal Biopsy ◽  
Mixed Venous Blood ◽  
Calcium Diet ◽  
Low Calcium Diet ◽  
Low Calcium

We have developed a radioimmunoassay for porcine intestinal calcium-binding protein (CaBP) and have used it to detect CaBP in pig plasma. Plasma CaBP is identical to intestinal CaBP on the basis of immunological activity, molecular size, and molecular charge properties. The plasma CaBP concentration was greater in the portal blood than in mixed venous blood, suggesting that blood CaBP originates in the gut. Two of four 15-week-old littermate pigs were placed on a low calcium diet (0.15% calcium, 0.65% phosphorus) and two on a control diet (0.65% calcium, 0.65% phosphorus). After 2 weeks, the entire small intestine was removed and divided into nine 1.8-m segments. CaBP was assayed in both plasma and intestinal mucosa. When the two pigs on a low calcium diet were compared with two control pigs, there was a general increase in immunoreactive CaBP in both plasma and intestinal mucosa. However, there was no increment in immunoreactive CaBP in the first 1.8-m segment of small intestine. Seventy-one percent of the increment in CaBP occurred distal to the first two segments. The largest fractional low calcium diet effect occurred in the ileum. The mean CaBP concentration for the total small intestine increased by a factor of 1.9. The plasma CaBP concentration increased by a factor of 2.6. In these pigs, plasma CaBP was a more reliable indicator of change in CaBP status than was the measurement in the proximal gut segment which contained the duodenum. The assay of CaBP in blood is convenient and may obviate the sampling errors inherent in intestinal biopsy.

Regulation of intestinal calcium-binding protein calcium intake in the rat

1975 ◽  
Vol 228 (3) ◽  
pp. 861-869 ◽  
Author(s):  
T Freund ◽  
F Bronner
Keyword(s):  
Calcium Intake ◽  
Calcium Binding ◽  
Calcium Concentration ◽  
Binding Protein ◽  
Calcium Binding Protein ◽  
Competitive Binding Assay ◽  
Calcium Diet ◽  
Low Calcium Diet ◽  
Low Calcium ◽  
High Calcium

Analytical gel electrophoresis of the vitamin D-dependent intestinal calcium-binding protein (CaBP) has demonstrated two protein bands (1 and 2) of similar molecular weight and similar specific binding activity. The mucosal concentration of CaBP, measured by a quantitative competitive binding assay, has been shown to vary reproducibly and inversely with calcium intake and the mucosal calcium concentration. These same factors also influence the relationship of bands 1 and 2. When animals on a high-calcium diet were placed on a low-calcium diet, their CaBP increased by 35% in 24 h and by 48% in 48 h and reached a level typical of animals on a low-calcium diet. Measurement of the diurnal variation of CaBP and mucosal calcium in animals allowed access to feed only at night revealed significant, but inverse, oscillations. These observations are interpreted as reflecting a regulation of CaBP by the mucosal calcium concentration, which appears to reflect absorbed calcium in transit.

EFFECT OF LOW PHOSPHORUS DIETS ON INTESTINAL CALCIUM ABSORPTION AND THE CONCENTRATION OF CALCIUM-BINDING PROTEIN IN INTACT AND PARATHYROIDECTOMIZED PIGS

1978 ◽  
Vol 78 (3) ◽  
pp. 379-387 ◽  
Author(s):  
J. FOX ◽  
D. W. PICKARD ◽  
A. D. CARE ◽  
T. M. MURRAY
Keyword(s):  
Small Intestine ◽  
Intestinal Absorption ◽  
Calcium Binding ◽  
Calcium Absorption ◽  
Binding Protein ◽  
Calcium Binding Protein ◽  
Intestinal Calcium Absorption ◽  
Jejunal Loop ◽  
Dietary Concentration ◽  
Low Phosphorus

The effect of changing the dietary concentration of phosphorus on the intestinal absorption of calcium has been studied in conscious pigs each prepared with a Thiry–Vella loop of jejunum. A reduction in the percentage of phosphorus in the diet from 0·7 to 0·3% caused an increase in the efficiency of absorption of calcium from the fluid used to perfuse the jejunal loop in both intact and parathyroidectomized animals. There was a marked increase in the amount of calcium-binding protein (CaBP) in the small intestine of pigs fed the low phosphorus diet. Parathyroidectomy did not affect the amount of CaBP in the small intestine when either the normal or the low phosphorus diets were fed.

scholarly journals The response of the small intestine to vitamin D. Correlation between calcium-binding-protein production and increased calcium absorption

1974 ◽  
Vol 144 (2) ◽  
pp. 339-346 ◽  
Author(s):  
J S Emtage ◽  
D E M Lawson ◽  
E Kodicek
Keyword(s):  
Vitamin D ◽  
Protein Synthesis ◽  
Small Intestine ◽  
Calcium Binding ◽  
Protein Production ◽  
Calcium Absorption ◽  
Binding Protein ◽  
Calcium Binding Protein ◽  
Intestinal Cell ◽  
Stimulation Of

1. The synthesis of calcium-binding protein, a protein produced in the small intestine in response to vitamin D, was investigated with a view to determining whether calcium-binding-protein production could be correlated with the stimulation of calcium absorption by vitamin D. 2. A radioimmunological assay, which can quantitatively estimate calcium-binding-protein concentrations as low as 1μg/g wet wt., was used to detect the synthesis of soluble calcium-binding protein. 3. When used on intestinal supernatants from chicks dosed with vitamin D, calcium-binding protein was not detectable at 8h but was present after 12h at a concentration of 8.6μg/g wet wt.; in agreement with this an increase in calcium absorption due to vitamin D was detected at 12h but not at 8h. 4. The synthesis of calcium-binding protein was also monitored directly by making use of the ability of the iodinated antiserum to bind specifically to nascent calcium-binding protein chains on intestinal polyribosomes; in this way calcium-binding-protein synthesis could be detected 8h after dosage with vitamin D. Further, the binding reaction indicated a near linear increase in the calcium-binding-protein-synthesizing capacity over a 16h period. 5. From the amount of calcium-binding protein present 12 and 24h after vitamin D administration it is calculated that calcium-binding-protein mRNA is produced at approx. 1mol/min per intestinal cell. 6. It is concluded that the high correlation between the initiation of calcium-binding-protein synthesis and the stimulation of calcium absorption by vitamin D strengthens the proposal that calcium-binding protein plays an important role in calcium transport.

Raised levels of calcium-binding protein in plasma following insulin-induced hypoglycaemia in the pig

1986 ◽  
Vol 109 (1) ◽  
pp. 101-106 ◽  
Author(s):  
E. M. W. Maunder ◽  
A. V. Pillay ◽  
C. Chapman ◽  
A. D. Care
Keyword(s):  
Vitamin D ◽  
Calcium Binding ◽  
Inorganic Phosphate ◽  
Binding Protein ◽  
Plasma Concentrations ◽  
Calcium Binding Protein ◽  
Insulin Administration ◽  
Calcium Diet ◽  
Low Calcium Diet ◽  
Normal Calcium

ABSTRACT Insulin-induced hypoglycaemia in the pig elicited sharp increases in the plasma concentrations of vitamin D-dependent calcium-binding protein (CaBP) and cortisol and a decrease in plasma inorganic phosphate. Glucose infusion following insulin administration abolished the increases in plasma CaBP and cortisol in response to insulin and reduced the hypophosphataemia. The percentage increases in plasma CaBP and cortisol in response to insulin-induced hypoglycaemia were reduced when the pigs were fed a low-calcium diet, but the hypophosphataemic response was similar. We conclude that insulin-induced hypoglycaemia leads to increased plasma CaBP in pigs fed a normal calcium diet, which is associated with the hypoglycaemia rather than being a direct effect of insulin. We therefore suggest that plasma CaBP may represent more than a mere uncontrolled leak from its sites of storage. J. Endocr. (1986) 109, 101–106

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