Mucosal calcium uptake by rat cecum: identity with transcellular calcium absorption

1983 ◽  
Vol 244 (6) ◽  
pp. G618-G622
Author(s):  
H. N. Nellans ◽  
R. S. Goldsmith
Keyword(s):  
Calcium Binding ◽  
Calcium Uptake ◽  
Calcium Absorption ◽  
Calcium Influx ◽  
Maximal Velocity ◽  
Similar Reduction ◽  
High Calcium ◽  
Wide Range ◽  
Rat Cecum

Unidirectional intestinal calcium uptake (JCame) at the mucosal surface of rat cecum was investigated in vitro with intact tissue. Uptake is linear for 2–3 min with no indication of rapid calcium binding. Kinetic parameters reveal a maximal velocity of 333 nmol . cm-2 . h-1 with a half-maximal concentration of 0.98 mM. High-calcium diet decreased JCame by more than 60% with respect to both control and low-calcium diets; 1 mM N-ethylmaleimide caused a similar reduction. The activation energy of JCame is significantly less than that of transepithelial mucosal-to-serosal calcium absorption. Mucosal uptake was compared with transepithelial calcium fluxes in rat cecum and revealed a 1:1 correlation over a wide range of transport rates. These results are interpreted to implicate a feedback control system between basolateral calcium efflux and brush-border calcium influx.

scholarly journals Promoting the Calcium-Uptake Bioactivity of Casein Phosphopeptides in vitro and in vivo

2021 ◽  
Vol 8 ◽  
Author(s):  
Guo Liu ◽  
Baoyan Guo ◽  
Shengwei Sun ◽  
Minna Luo ◽  
Fei Liu ◽  
...  
Keyword(s):  
Calcium Binding ◽  
Calcium Transport ◽  
Calcium Uptake ◽  
Calcium Absorption ◽  
Serum Alkaline Phosphatase ◽  
Binding Capacity ◽  
Animal Experiments ◽  
Casein Phosphopeptides

Casein phosphopeptides have been studied widely for their ability to chelate calcium. However, systematic studies on the effects of casein phosphopeptides (CPP) on calcium absorption in vitro and in vivo are scarce. The purities of two commercially available products, CPP1 and CPP2, are 18.37 and 25.12%, respectively. Here, the in vitro calcium binding capacity of CPP2 was 142.56 ± 7.39 mg/g, which was higher than that of CPP1 (107.15 ± 6.27 mg/g). The calcium transport results in a Caco-2 monolayer model indicated that, relative to controls, CPP1 and CPP2 increased calcium transport by 21.78 and 53.68%, respectively. Subsequent animal experiments showed that the CPP2-Ca-H group (1% Ca, 0.4% CPP2) had significant increases in the femur index, serum Ca2+ and serum osteocalcin levels, and femoral Ca content. The CPP2-Ca-H animal also had decreased serum alkaline phosphatase levels, parathyroid hormone content, and urinary pyridinoline content. Overall, our results demonstrated that CPP2 had stronger effects on promoting calcium uptake than CPP1.

Transepithelial calcium transport by rat cecum: high-efficiency absorptive site

1981 ◽  
Vol 240 (6) ◽  
pp. G424-G431 ◽  
Author(s):  
H. N. Nellans ◽  
R. S. Goldsmith
Keyword(s):  
Calcium Transport ◽  
High Efficiency ◽  
Calcium Absorption ◽  
Short Circuit ◽  
Calcium Fluxes ◽  
Calcium Diet ◽  
Low Calcium Diet ◽  
High Calcium ◽  
Rat Cecum

Transepithelial calcium transport has been investigated in rat cecum under in vitro voltage-clamp conditions. Under short-circuit conditions, the cecum behaves as a relatively tight epithelium for calcium fluxes, where mucosal-to-serosal (JCam leads to s) flux exceeds the reverse flux by at least 15-fold. JCanet is abolished in the presence of 1 mM N-ethylmaleimide, is inhibited by 40% with 1 mM ouabain, and is decreased by at least 60% when medium sodium is replaced by choline. Voltage-clamping experiments suggest that both electroneutral- and electrogenic-mediated calcium fluxes traverse the cell in the mucosal-to-serosal direction. Serosal-to-mucosal flux is purely diffusional and probably constrained to the paracellular pathway. In rats weighing less than 175 g, a low-calcium diet has no significant stimulatory effect on JCam leads to s, but a high-calcium diet markedly reduces this flux. These results suggest that the cecum possesses the highest density of calcium transport sites in the rat intestine and is ideally suited for bulk calcium absorption, which may be “down regulated” in response to an increased calcium load in growing animals.

Activity-Related Calcium Dynamics in Motoneurons of the Nucleus Hypoglossus From Mouse

1999 ◽  
Vol 82 (6) ◽  
pp. 2936-2946 ◽  
Author(s):  
Mario B. Lips ◽  
Bernhard U. Keller
Keyword(s):  
Quantitative Analysis ◽  
Action Potential ◽  
Calcium Binding ◽  
Calcium Influx ◽  
Binding Capacity ◽  
Calcium Transients ◽  
Calcium Dynamics ◽  
The Brain

A quantitative analysis of activity-related calcium dynamics was performed in motoneurons of the nucleus hypoglossus in the brain stem slice preparation from mouse by simultaneous patch-clamp and microfluorometric calcium measurements. Motoneurons were analyzed under in vitro conditions that kept them in a functionally intact state represented by rhythmic, inspiratory-related bursts of excitatory postsynaptic currents and associated action potential discharges. Bursts of electrical activity were paralleled by somatic calcium transients resulting from calcium influx through voltage-activated calcium channels, where each action potential accounted for a calcium-mediated charge influx around 2 pC into the somatic compartment. Under in vivo conditions, rhythmic-respiratory activity in young mice occurred at frequencies up to 5 Hz, demonstrating the necessity for rapid calcium elevation and recovery in respiratory-related neurons. The quantitative analysis of hypoglossal calcium homeostasis identified an average extrusion rate, but an exceptionally low endogenous calcium binding capacity as cellular parameters accounting for rapid calcium signaling. Our results suggest that dynamics of somatic calcium transients 1) define an upper limit for the maximum frequency of respiratory-related burst discharges and 2) represent a potentially dangerous determinant of intracellular calcium profiles during pathophysiological and/or excitotoxic conditions.

CALCIUM INFUSION IN THE DETECTION OF BONE DISEASE IN PARATHYROID DISORDERS

1963 ◽  
Vol 43 (2) ◽  
pp. 170-183 ◽  
Author(s):  
Heinrich G. Haas ◽  
John J. Canary ◽  
Laurence H. Kyle ◽  
Daniel H. Mintz
Keyword(s):  
Alkaline Phosphatase ◽  
Calcium Absorption ◽  
Osteitis Fibrosa ◽  
Idiopathic Hypercalciuria ◽  
Calcium Excretion ◽  
List Type ◽  
Elevated Alkaline Phosphatase ◽  
Calcium Retention ◽  
High Calcium ◽  
Wide Range

ABSTRACT The retention of an infused load of calcium was determined under standard conditions in 25 patients with various parathyroid disorders, in 12 normal control subjects, and in 3 patients with idiopathic hypercalciuria. A normal range of 40–60 per cent calcium-retention was found, and there was some support to the thesis that hypercalciuria per se may lower the retention of calcium. Patients with primary hyperparathyroidism showed a wide range of calcium retention reflecting on one side probably hypercalciuria (low calcium retention) and on the other osteitis fibrosa generalisata (high calcium retention). In detecting early bone involvement in parathyroid hyperfunction, the calcium retention test was of equal or greater value than alkaline phosphatase determination in the serum. In secondary hyperparathyroidism due to severe renal insufficiency, a high calcium retention was seen pointing either to delayed calcium excretion (low GFR) or increased avidity of the skeleton for calcium as a consequence of an admixture of osteomalacia and osteitis fibrosa. All hypoparathyroid patients retained large quantities of calcium. In three of these cases, an elevated alkaline phosphatase level indicated osteomalacia, possibly following inadequate calcium absorption from the gut, while in two patients a low filtered load of calcium accounted for the apparent high calcium retention.

scholarly journals Relocation of annexin V to platelet membranes is a phosphorylation-dependent process

1997 ◽  
Vol 328 (2) ◽  
pp. 447-452 ◽  
Author(s):  
J. Patrick TROTTER ◽  
A. Margaret ORCHARD ◽  
H. John WALKER
Keyword(s):  
Protein Phosphatase ◽  
Calcium Binding ◽  
Kinase Inhibitor ◽  
Annexin V ◽  
Intact Cells ◽  
Platelet Membranes ◽  
Wide Range ◽  
In Vitro Reconstitution ◽  
Tight Association

Annexins are a family of calcium-binding proteins that have been implicated in a wide range of intracellular processes. We have previously reported that stimulation of platelets with agents that increase intracellular [Ca2+] induces the relocation of annexin V to membranes, and that this annexin V may be binding to a 50 kDa protein located within platelet membranes. We report here, using an in vitro reconstitution system, that the relocation of annexin V to membranes is enhanced by ATP. We also demonstrate that when adenosine 5ʹ-[γ-thio]-triphosphate, which can replace ATP in phosphorylation reactions, is substituted for ATP, the amount of annexin V that binds to membranes is further increased. In separate experiments using intact cells, we show that the protein phosphatase inhibitor okadaic acid mimics the action of the physiological agonist thrombin, in that it induces annexin V to bind to membranes and that the addition of the protein kinase inhibitor staurosporine inhibits A23187-induced relocation of annexin V. In addition, alkaline phosphatase, when added to isolated membranes, was found to remove endogenous annexin V from the membranes. Furthermore, immunoprecipitation of 33P-labelled proteins indicated that annexin V may form a multi-protein complex including phosphoproteins of 25, 50 and 83 kDa. Taken together these observations suggest that, following physiological activation, the phosphorylation of one or more proteins is responsible for the tight association of annexin V with platelet membranes and the subsequent regulation of membrane localized processes.

scholarly journals Calcium can mobilize and activate myosin-VI

2016 ◽  
Vol 113 (9) ◽  
pp. E1162-E1169 ◽  
Author(s):  
Christopher Batters ◽  
Dario Brack ◽  
Heike Ellrich ◽  
Beate Averbeck ◽  
Claudia Veigel
Keyword(s):  
Binding Site ◽  
Calcium Binding ◽  
Calcium Flux ◽  
Particle Analysis ◽  
Myosin Vi ◽  
Electron Microscopic ◽  
Iq Motif ◽  
Lever Arm ◽  
High Calcium ◽  
Wide Range

The ability to coordinate the timing of motor protein activation lies at the center of a wide range of cellular motile processes including endocytosis, cell division, and cancer cell migration. We show that calcium dramatically alters the conformation and activity of the myosin-VI motor implicated in pivotal steps of these processes. We resolved the change in motor conformation and in structural flexibility using single particle analysis of electron microscopic data and identified interacting domains using fluorescence spectroscopy. We discovered that calcium binding to calmodulin increases the binding affinity by a factor of 2,500 for a bipartite binding site on myosin-VI. The ability of calcium-calmodulin to seek out and bridge between binding site components directs a major rearrangement of the motor from a compact dormant state into a cargo binding primed state that is nonmotile. The lack of motility at high calcium is due to calmodulin switching to a higher affinity binding site, which leaves the original IQ-motif exposed, thereby destabilizing the lever arm. The return to low calcium can either restabilize the lever arm, required for translocating the cargo-bound motors toward the center of the cell, or refold the cargo-free motors into an inactive state ready for the next cellular calcium flux.

Glucose enhancement of transcellular calcium transport in the intestine

1988 ◽  
Vol 255 (3) ◽  
pp. G339-G345 ◽  
Author(s):  
K. M. Carroll ◽  
R. J. Wood ◽  
E. B. Chang ◽  
I. H. Rosenberg
Keyword(s):  
Calcium Transport ◽  
Calcium Uptake ◽  
Calcium Absorption ◽  
Membrane Integrity ◽  
Calcium Flux ◽  
Calcium Efflux ◽  
Cell Membrane Integrity ◽  
Active Calcium ◽  
Altered Cell

Glucose stimulates calcium transport in vitro in rat duodenal tissue and isolated enterocytes. Under short-circuited conditions, glucose increased mucosal to serosal calcium flux (JCa(m----s)) without altering serosal to mucosal calcium flux (JCa(s----m)) in the duodenum, the primary site of active calcium absorption in the rat small intestine. The half-maximal dose (ED50) of the glucose stimulatory effect was less than 1 mM, and an increase in JCa(m----s) of 80% over control was seen at a glucose concentration of 50 mM. Glucose did not increase calcium flux in the ileum where active calcium absorption is minimal. Glucose stimulated net calcium uptake by 35% in isolated duodenal enterocytes. Glucose did not alter calcium efflux from preloaded enterocytes suspended in calcium-free buffer. Glucose enhancement of net calcium uptake in enterocytes was not caused by altered cell membrane integrity or functional viability. The nonmetabolizable glucose analogue alpha-methylglucoside did not stimulate calcium transport. Our findings suggest that glucose can stimulate intestinal calcium absorption, at least partially, by enhancing transcellular calcium transport and that cellular glucose metabolism is necessary for stimulation of this route of calcium transport.

Lipids and calcium uptake of sperm in relation to cold shock and preservation: a review

1993 ◽  
Vol 5 (6) ◽  
pp. 639 ◽  
Author(s):  
IG White
Keyword(s):  
Fatty Acid ◽  
Calcium Uptake ◽  
Cold Shock ◽  
Freezing Point ◽  
Fatty Acid Content ◽  
Calcium Flux ◽  
High Unsaturated Fatty Acid ◽  
High Calcium ◽  
Ram Sperm

When sperm of the ram, bull, boar and stallion are cold-shocked by rapid cooling to near freezing point, motility and metabolic activity are irreversibly depressed and the acrosome and plasma membrane disrupted. Ram sperm become susceptible to cold shock in the proximal corpus region of the epididymis when the cytoplasmic droplet has moved backwards to the distal portion of the sperm midpiece. The membrane constituents phospholipids and cholesterol are important in cold shock which causes loss of lipid from sperm. The susceptibility of sperm to cold shock is linked with a high ratio of unsaturated:saturated fatty acids in the phospholipids and a low cholesterol content. The high unsaturated fatty acid content of sperm also makes them susceptible to damage from peroxidation which adversely affects motility, metabolism, ultrastructure and fertility. Hydroxynonenal, a product of fatty acid peroxidation, depresses the motility and oxygen uptake of ram sperm in vitro and may react with the -SH groups of the axonemal microtubules. High calcium concentrations in the external medium may decrease the motility and metabolism of sperm and 'calcium intoxication' may be a factor in cold shock. Lowering the environmental temperature increases calcium uptake by sperm and the effect is aggravated if the rate of cooling is rapid. Phospholipids, particularly those in egg yolk, protect sperm to some extent from cold shock and also prevent increased calcium flux into the sperm. Suggestions are made for increasing the life span of sperm during preservation and microencapsulation by adding agents that may stabilize membranes, counter peroxidation and decrease calcium uptake.

scholarly journals Elucidating the Calcium-Binding Site, Absorption Activities, and Thermal Stability of Egg White Peptide–Calcium Chelate

Foods ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2565
Author(s):  
Zhijie Bao ◽  
Penglin Zhang ◽  
Na Sun ◽  
Songyi Lin
Keyword(s):  
Calcium Binding ◽  
Calcium Absorption ◽  
Binding Capacity ◽  
Egg White ◽  
Absorption Capacity ◽  
Spherical Particles ◽  
Calcium Binding Site ◽  
Peptide Bonds ◽  
High Calcium ◽  
Α Helix

With the current study, we aimed to determine the characteristics and calcium absorption capacity of egg white peptide–calcium complex (EWP-Ca) and determine the effect of sterilization on EWP-Ca to study the possibility of EWP-Ca as a new potential calcium supplement. The results of SEM and EDS showed a high calcium chelating ability between EWP and calcium, and the structure of EWP-Ca was clustered spherical particles due its combination with calcium. The FTIR and Raman spectrum results showed that EWP could chelate with calcium by carboxyl, phosphate, and amino groups, and peptide bonds may also participate in peptide–calcium binding. Moreover, the calcium absorption of EWP-Ca measured by the intestinal everted sac model in rats was 32.38 ± 6.83 μg/mL, significantly higher than the sample with CaCl2, and the mixture of EWP and Ca (p < 0.05) revealed appropriate calcium absorption capacity. The fluorescence spectra and CD spectra showed that sterilization caused a decrease in the content of α-helix and β-sheet and a significant increase in β-turn (p < 0.05). Sterilization changed the EWP-Ca structure and decreased its stability; the calcium-binding capacity of EWP-Ca after sterilization was decreased to 41.19% (p < 0.05). Overall, these findings showed that EWP could bind with calcium, form a peptide–calcium chelate, and serve as novel carriers for calcium supplements.

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