scholarly journals Hormonal and dietary influences on true fractional calcium absorption in women: role of obesity

2012 ◽  
Vol 23 (11) ◽  
pp. 2607-2614 ◽  
Author(s):  
S. A. Shapses ◽  
D. Sukumar ◽  
S. H. Schneider ◽  
Y. Schlussel ◽  
R. E. Brolin ◽  
...  
Keyword(s):  
Calcium Absorption ◽  
Fractional Calcium Absorption

Changes in the regulation of calcium metabolism and bone calcium content during growth in the absence of endogenous prolactin and during hyperprolactinemia: A longitudinal study in male and female Wistar rats

2000 ◽  
Vol 78 (10) ◽  
pp. 757-765 ◽  
Author(s):  
Pritsana Piyabhan ◽  
Nateetip Krishnamra ◽  
Liangchai Limlomwongse
Keyword(s):  
Calcium Metabolism ◽  
Wistar Rats ◽  
Calcium Absorption ◽  
Calcium Content ◽  
Female Rats ◽  
Calcium Retention ◽  
Bone Calcium ◽  
Female Wistar Rats ◽  
Fractional Calcium Absorption

Since endogenous prolactin has been shown to enhance food consumption, calcium absorption, and bone calcium turnover in the pregnant rat, the role of endogenous prolactin in the regulation of calcium metabolism was investigated in 3-day balance studies of female Wistar rats from the age of 3 to 11 weeks. The study was divided into two parts. In part I, calcium metabolism in males and females was compared. In part II, 3-week old female rats were divided into 5 groups: (i) control animals receiving 0.9% NaCl; (ii) animals receiving 6 mg bromocriptine/kg/day (- PRLendo group); (iii) animals receiving 2.5 mg ovine prolactin/kg/day (+PRLexo); (iv) sham-operated animals receiving 0.9% NaCl, and (v) animals with two extra pituitaries implanted under the renal capsule, receiving 0.9% NaCl (AP group). Results showed that rapid growth occurred between 3 and 6 weeks with maximum fractional calcium absorption and calcium retention at 5 weeks of age in both sexes. The data also showed a physiological significance of endogenous prolactin in enhancing calcium absorption and retention in 5 week old rats. In an absence of prolactin, peak calcium absorption was delayed in 7-week old animals, and vertebral calcium content of 11-week old animals was reduced by 18%. Hyperprolactinemia in the AP group was found to enhance fractional calcium absorption and calcium retention at 7, 9, and 11 weeks and increased the femoral calcium content by 16%. It could be concluded that a physiological role of prolactin is the stimulation of calcium absorption and maintainance of bone calcium content during growth and development.Key words: bone calcium content, calcium absorption, calcium balance, hyperprolactinemia, prolactin.

Role of facilitated diffusion of calcium by calbindin in intestinal calcium absorption

1992 ◽  
Vol 262 (2) ◽  
pp. C517-C526 ◽  
Author(s):  
J. J. Feher ◽  
C. S. Fullmer ◽  
R. H. Wasserman
Keyword(s):  
Negative Feedback ◽  
Calcium Absorption ◽  
Feedback Inhibition ◽  
Basolateral Membrane ◽  
Reaction Diffusion ◽  
Diffusion Problem ◽  
Facilitated Diffusion ◽  
Calbindin D9k ◽  
And Diffusion

Computer simulations of transcellular Ca2+ transport in enterocytes were carried out using the simulation program SPICE. The program incorporated a negative-feedback entry of Ca2+ at the brush-border membrane that was characterized by an inhibitor constant of 0.5 microM cytosolic Ca2+ concentration ([Ca2+]). The basolateral Ca(2+)-ATPase was simulated by a four-step mechanism that resulted in Michaelis-Menten kinetics with a Michaelis constant of 0.24 microM [Ca2+]. The cytosolic diffusion of Ca2+ was simulated by dividing the cytosol into 10 slabs of equal width. Ca2+ binding to calbindin-D9K was simulated in each slab, and diffusion of free Ca2+, free calbindin, and Ca(2+)-laden calbindin was simulated between each slab. The cytosolic [Ca2+] of the simulated cells was regulated within the physiological range. Calbindin-D9K reduced the cytosolic [Ca2+] gradient, increased Ca2+ entry into the cell by removing the negative-feedback inhibition of Ca2+ entry, increased cytosolic Ca2+ flow, and increased the efflux of Ca2+ across the basolateral membrane by increasing the free [Ca2+] immediately adjacent to the pump. The enhancement of transcellular Ca2+ transport was nearly linearly dependent on calbindin-D9K concentration. The values of the dissociation constant (Kd) for calbindin-D9K were previously obtained experimentally in the presence and absence of KCl. Calbindin with the Kd obtained in the presence of KCl enhanced the simulated Ca2+ transport more than with the Kd obtained in the absence of KCl. This result suggests that the physiological Kd of calbindin is optimal for the enhancement of transcellular Ca2+ transport. The simulated Ca2+ flow was less than that predicted from the "near-equilibrium" analytic solution of the reaction-diffusion problem.

Estrogen Regulates Duodenal Calcium Absorption Through Differential Role of Estrogen Receptor on Calcium Transport Proteins

2020 ◽  
Vol 65 (12) ◽  
pp. 3502-3513 ◽  
Author(s):  
Xubiao Nie ◽  
Hai Jin ◽  
Guorong Wen ◽  
Jingyu Xu ◽  
Jiaxing An ◽  
...  
Keyword(s):  
Estrogen Receptor ◽  
Calcium Transport ◽  
Calcium Absorption ◽  
Transport Proteins

The Role of Bile in Calcium Absorption

1958 ◽  
Vol 66 (1) ◽  
pp. 45-54 ◽  
Author(s):  
F. W. Lengemann ◽  
J. W. Dobbins
Keyword(s):  
Calcium Absorption

Effect of hypercalcemia on renal tubular handling of calcium and magnesium

1982 ◽  
Vol 60 (10) ◽  
pp. 1275-1280 ◽  
Author(s):  
Gary A. Quamme
Keyword(s):  
Urinary Excretion ◽  
Calcium Absorption ◽  
Sodium Absorption ◽  
Loop Of Henle ◽  
Magnesium Transport ◽  
Acute Elevation ◽  
Fractional Calcium Absorption ◽  
Calcium And Magnesium ◽  
Renal Tubular

Tubular calcium and magnesium transport was investigated in thyroparathyroidectomized rats following acute elevation of extracellular calcium concentration. Fractional urinary excretion of calcium increased from 0.2 to 8.3% and magnesium increased from 15 to 39%, while sodium increased modestly from 0.1 to 1.1%. Superficial proximal tubules, Henle's loop, and distal tubules were perfused in vivo to determine the segmental effects of hypercalcemia. Fractional calcium absorption within the loop of Henle was significantly less in the hypercalcemie rats (58%) compared with normal animals (86%). Magnesium transport was inhibited to a greater extent compared with calcium in the loop as the fractional reabsorption decreased from 78% in the normal rats to 35% in the hypercalcemie animals. Sodium absorption was inhibited by 8%. Absolute calcium and magnesium absorption within the superficial distal convoluted tubule increased about three- to four-fold with increased delivery to this segment. These data indicate that hypercalcemia inhibits calcium and magnesium transport relatively more than sodium absorption in the loop of Henle and that this action principally accounts for the increase in urinary excretion of these electrolytes.

Role of prolactin in vitamin D metabolism and calcium absorption during lactation in the rat

1982 ◽  
Vol 94 (3) ◽  
pp. 443-453 ◽  
Author(s):  
C. J. Robinson ◽  
E. Spanos ◽  
M. F. James ◽  
J. W. Pike ◽  
M. R. Haussler ◽  
...  
Keyword(s):  
Vitamin D ◽  
Alkaline Phosphatase ◽  
Parathyroid Hormone ◽  
Alkaline Phosphatase Activity ◽  
Plasma Levels ◽  
Calcium Absorption ◽  
High Plasma ◽  
Intestinal Calcium Absorption ◽  
Vitamin D Metabolism

Intestinal calcium absorption and plasma levels of 1,25-dihydroxycholecalciferol (1,25(OH)2D3) were measured in lactating and non-lactating rats and the effects of bromocriptine and exogenous prolactin treatment were evaluated. In lactating rats calcium absorption and plasma levels of parathyroid hormone, 1,25(OH)2D3 and alkaline phosphatase activity were significantly increased. Bromocriptine treatment significantly reduced the enhanced calcium absorption and levels of plasma 1,25(OH)2D3 and alkaline phosphatase but had no significant effect on plasma levels of parathyroid hormone. Prolactin administered with bromocriptine to lactating animals prevented all the changes observed with bromocriptine treatment alone. It was concluded that the increased plasma levels of prolactin during lactation lead to high plasma levels of 1,25(OH)2D3 which are responsible for the enhanced intestinal calcium absorption.

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