Effect of pH on interaction of calcium ions with serum proteins

1961 ◽  
Vol 201 (2) ◽  
pp. 386-392 ◽  
Author(s):  
N. A. Peterson ◽  
G. A. Feigen ◽  
J. M. Crismon

A study has been made of the effect of pH on the dissociation of calcium proteinate in rabbit serum. Equations were derived from the experimental data which define a) the effect of serum pH on the McLean-Hastings dissociation constant for the dissociation of calcium proteinate; b) the relationship between the serum pH and the concentration of calcium which is ultrafiltrable; c) the effects of pH, total protein, and total calcium concentration on the change in calcium ion concentration (ultrafiltrable calcium) per unit change in pH. A simple, linear equation was derived from the data which gives serum ultrafiltrable calcium concentration in terms of pH, total protein, and total calcium concentration. A similar study on the dissociation of calcium proteinate was made on purified bovine serum albumin. The results obtained with this system were similar to those obtained on rabbit serum, but the scattering of the data in the case of the purified protein system was far less pronounced. The data on purified albumin was used to re-examine some of the relationships which were derived from the data on rabbit serum.

1982 ◽  
Vol 243 (2) ◽  
pp. G134-G140
Author(s):  
W. J. Snape

The purpose of this study was to compare the effect of altering the extracellular calcium ion concentration on bethanechol or octapeptide of cholecystokinin (OP-CCK) stimulation of the isolated transverse colon of the cat. Myoelectric activity was recorded with monopolar glass-pore electrodes. Bethanechol (10(-6) M) stimulated an increase in the number of slow waves with superimposed spike potentials to 85.5 +/- 5.3% (P less than 0.001) compared with the basal spike activity (8.9 +/- 1.4%). OP-CCK (4 x 10(-9)) also increased spike activity (80.7 +/- 3.8%, P less than 0.001), which was not inhibited by atropine, phentolamine, or propranolol. Addition of 0.0 mM calcium solution to the colonic smooth muscle abolished both slow-wave and spike activity, which returned after replacing 0.25 mM calcium in the solution. Bethanechol stimulated a greater increase in spike activity as the concentration of calcium was increased. OP-CCK stimulation of colonic spike activity was more sensitive to the extracellular calcium concentration than bethanechol stimulation. Verapamil had a minimal effect on bethanechol stimulation of colonic spike activity, but it inhibited the OP-CCK stimulation. These studies suggest that 1) OP-CCK appears to stimulate colonic smooth muscle directly and 2) OP-CCK requires the presence of a greater amount of extracellular ionic calcium in order to stimulate colonic spike activity compared with bethanechol.


The sera of non-pregnant adult rabbits which had been hyperimmunized to Brucella abortus antigen, the sera of pregnant female rabbits which had not been immunized, and the sera, exocoelomic fluids, amniotic fluids and stomach contents of 25-day-old foetal rabbits were examined electrophoretically and ultracentrifugally. The serum of pregnant rabbits differed both in total protein concentration and in the proportions of the components from that of non-pregnant hyperimmunized rabbits. The foetal sera contained components corresponding to albumin, α-, β- and γ -globulin, but the proportions of these components, as well as the total protein concentrations, differed widely from those of the sera of both pregnant and non-pregnant adults. Foetal exocoelomic fluid, amniotic fluid and stomach contents contain similar electrophoretic components and resemble each other closely in the proportions of the components, though differing in the total concentrations. The components resemble those of sera in mobility, but the proportions of the components differ widely from those of the sera, both foetal and adult. Various experimental procedures to which rabbits were subjected resulted, after 24 h, in a significant increase in the total protein concentrations, without any corresponding change in the proportions of the components, of the foetal sera. No corresponding changes were detected in the maternal sera. The effect on the sera could be explained by withdrawal of water alone from the foetal circulation. Using antibodies as markers, it was shown that both β - and γ -globulin enter the foetal circulation from immune rabbit serum injected into the uterine lumen. The importance of the contribution of maternal serum proteins to the foetus is discussed in the light of the immunological and electrophoretic results.


PEDIATRICS ◽  
1950 ◽  
Vol 6 (3) ◽  
pp. 361-370
Author(s):  
R. AMES ◽  
I. SYLLM ◽  
S. RAPOPORT

The effect of infusions of citrated plasma given at varying rates on the plasma citrate level of infants has been studied. The plasma citrate as a rule rose from 0.17 to 2.0 mM/1. after single infusions to fall rapidly at first and more slowly later. In two instances levels of 2.6 and 2.8 mM/1. were observed. Considerable decreases in the calcium ion concentration, assuming unchanged total calcium values, were calculated. ECGs indicated some lengthening of the duration of the Q-T interval, compatible with a decrease in the calcium ion concentration, but to a degree less than expected. One infant suffered a nearly fatal reaction, considered to be tetanic in nature. The examination of the citrate in the plasma of an infant dead after infusion of plasma showed a high citrate level of 2.8 mM/1. It is assumed that normally physiologic forces are operative to counteract the calcium-ion-lowering effect of citrate.


1955 ◽  
Vol 22 (1) ◽  
pp. 60-68 ◽  
Author(s):  
G. T. Pyne ◽  
Kathleen A. McHenry

1. A study of the compositional factors which affect the heat coagulation of milk has been undertaken.2. Calcium-ion concentration and colloidal phosphate content appear to be the chief factors determining the tendency of a milk to coagulate on heating.3. Acidity (mainly derived from thermal decomposition of lactose and casein) and heat denaturation of casein are supplementary coagulation factors which develop during the heating process.4. Lactose, as the main source of heat-developed acidity, is an important secondary factor in heat coagulation, but not an essential one. Coagulation can proceed, though more slowly, in its absence. The serum proteins play no part in the phenomenon.5. A provisional theory of the heat coagulation of milk based on these findings is put forward.


2019 ◽  
Vol 15 ◽  
pp. 2801-2811 ◽  
Author(s):  
Aurélien Ducrot ◽  
Arnaud Tron ◽  
Robin Bofinger ◽  
Ingrid Sanz Beguer ◽  
Jean-Luc Pozzo ◽  
...  

Free calcium ion concentration is known to govern numerous biological processes and indeed calcium acts as an important biological secondary messenger for muscle contraction, neurotransmitter release, ion-channel gating, and exocytosis. As such, the development of molecules with the ability to instantaneously increase or diminish free calcium concentrations potentially allows greater control over certain biological functions. In order to permit remote regulation of Ca2+, a selective BAPTA-type synthetic receptor / host was integrated with a photoswitchable azobenzene motif, which upon photoirradiation would enhance (or diminish) the capacity to bind calcium upon acting on the conformation of the adjacent binding site, rendering it a stronger or weaker binder. Photoswitching was studied in pseudo-physiological conditions (pH 7.2, [KCl] = 100 mM) and dissociation constants for azobenzene cis- and trans-isomers have been determined (0.230 μM and 0.102 μM, respectively). Reversible photoliberation/uptake leading to a variation of free calcium concentration in solution was detected using a fluorescent Ca2+ chemosensor.


Author(s):  
Sujata M. Kasabe ◽  
Bajirao B. Ahire

During the last decade it became the subject of much attention by both scientists and the general public that in the biological system like many other inorganic elements calcium is the most important element. The central role of calcium is in mammalian bones and other mineralized tissues were recognised immediately after its discovery as an element by the scientist Davy in 1808. The insight arrived much later that calcium 2+ ions could play a very important role in other tissues as well. Nowadays, Ca2+ ions are widely recognised as central to a complex intracellular messenger system that is mediating a wide range of biological processes such as muscle contraction, secretion, glycolysis and glycogenesis, iron transport, cell division and growth [1–11]. In the case of mammals, the blood plasma in the Ca2+ Ion concentration exceeds the intracellular by factor of about 104 Ca2+ ions are instrumental in joining certain proteins in the blood clotting system with membrane surfaces of circulating cells. The stable isotopes of calcium are 40 Ca, 44 Ca, 42 Ca, 43 Ca, amid all 40 Ca is most abundant [12]. There are two main groups of experimental techniques for the measurement ofCa2+ion namely 1) Measurement of free calcium concentration. 2) Measurement of total calcium concentration. Approximately 1 kilogram of calcium is present in the human body of which more than 99% deposit is in the bone in the form of calcium phosphate [1]. The distribution of calcium 2+ Ion throughout the organism is demanded and should be made available where needed. In human beings, the blood plasma level of total calcium is kept constant (=2.45mM) within the narrow limits. On a cellular level the basal cytoplasmic calcium 2+concentration, at least in eukaryotic cells, is very low that is on the order of 100 nM. Whereas, at the same time the concentration of Ca2+ in certain organelles such as endoplasmic reticulum or mitochondria may be considerably higher [2,13]. Ca+ channels are regulated by chemical signalling, perhaps by hormones acting directly on the channel by small molecules released intracellularly when a hormone is attached to a membrane- bound receptor [lipard]. More than 99% of the calcium in the human body is in the bones and teeth. In bone, calcium provides the structural strength that allows the bone to support the body’s weight and anchor the muscles. Bone calcium also serves as a reservoir that can be tapped to maintain extracellular calcium concentration regardless of intake. Calcium differs from most other nutrients in that the body contains a substantial store, far in excess of short-term needs, but at the same time that store serves a critical structural role. Thus, the effects of calcium deficiency may escape notice for a considerable time, until they manifest as skeletal weakness or fractures. Deficiency of calcium bones becomes interstitial or brittle and osteoporosis gradually develops.


1977 ◽  
Vol 55 (3) ◽  
pp. 709-723 ◽  
Author(s):  
J. G. Foulks ◽  
Florence A. Perry

The electrical and mechanical behaviour of frog twitch muscle in response to changes in membrane potential has been examined over a wide range of hydrogen ion concentration (pH 3.0–11.0). The changes in resting and action potentials, twitches, and maximum potassium-induced contractures (K contractures) were remarkably small when the pH was varied between 5.0 and 10.0. The time course of action potentials generally displayed small graded changes with variation in pH, possibly as the result of changes in surface potential.The amplitude of twitches and maximum K contractures was substantially decreased when pH was reduced to 4.0 or raised to 11.0 without significant alteration in membrane resting potential or consistent suppression of excitation, but maximum caffeine-induced contractures were unchanged. Replacement of chloride with perchlorate promptly antagonized the depressant effects of pH extremes (4.0, 11.0) on both twitch amplitude and maximum K-contracture tension. Acid-induced reductions in maximum K-contracture tension also were partially antagonized by increased calcium concentration. The onset and recovery from the contraction-depressant effects of pH extremes were too slow to be explained by the titration of groups immediately accessible at the membrane surface but too rapid to be accounted for by changes in intracellular pH. Thus, excitation and contraction apparently were uncoupled by sufficient alteration in extracellular pH. Changes in external pH had little effect on the impairment of maximum K contractures by media lacking divalent cations, or on the restoration of such responses by perchlorate except at very alkaline pH (10.0–11.0).The threshold for K contractures was reduced at pH 11.0, but otherwise was little affected by variation in pH at normal concentrations of divalent cations. Altered pH did not modify the usual effects of increased calcium concentration on the relation between potassium concentration and K-contracture tension. When K contractures were maintained by perchlorate in the absence of divalent cations, hydrogen ions displayed calcium-like actions on the relation between external K concentration ([K]0) and K-contracture tension, and also on the time course of submaximum K contractures. These observations are compatible with similar effects of hydrogen and calcium ions on surface potential.The problem of identifying putative charged groups which might influence the linkage between contractile responses and changes in membrane potential is discussed.


1996 ◽  
Vol 314 (1) ◽  
pp. 347-354 ◽  
Author(s):  
M. D. BOOTMAN ◽  
K. W. YOUNG ◽  
J. M. YOUNG ◽  
R. B. MORETON ◽  
M. J. BERRIDGE

Stimulation of single HeLa cells with histamine evoked repetitive increases of the intracellular calcium ion concentration (Ca2+ spikes). The frequency of Ca2+ spiking increased as the extracellular hormone concentration was elevated. In addition, the frequency of Ca2+ spiking could be accelerated by increasing the extracellular Ca2+ concentration ([Ca2+]o) in the presence of a constant hormone concentration. The range of [Ca2+]o over which the spiking frequency could be titrated was nominally-zero to 10 mM, being half-maximally effective at approx. 1 and 2.5 mM for 37 and 22 °C respectively. The effect of [Ca2+]o on inositol phosphates production was also examined. Changes of [Ca2+]o over a range which had been found to affect the frequency of Ca2+ spiking did not have any effect on the rate of myo-inositol 1,4,5-trisphosphate (InsP3) production, although an increase in inositol phosphates production was observed as [Ca2+]o was increased from zero to values giving less than half-maximal Ca2+ spike frequency. These data suggest that at low Ca2+ spike frequency, Ca2+-stimulated activation of phospholipase C may contribute to Ca2+ spiking in HeLa cells, but under some conditions the availability of Ca2+ to the intracellular stores, rather than changes in the rate of InsP3 production, determines the Ca2+ spike frequency.


2010 ◽  
Vol 128 (5) ◽  
pp. 268-271 ◽  
Author(s):  
Alexandre de Andrade Sousa ◽  
José Maria Porcaro Salles ◽  
João Marcos Arantes Soares ◽  
Gustavo Meyer de Moraes ◽  
Jomar Rezende Carvalho ◽  
...  

CONTEXT AND OBJECTIVE: Magnesium ion concentration is directly related and phosphorus ion concentration is inversely related to calcemia. The aim of this study was to evaluate the evolution of magnesium and phosphorus ion levels in patients undergoing thyroidectomy and correlate these with changes to calcium concentration. DESIGN AND SETTING: Prospective study at the Alpha Institute of Gastroenterology, Hospital das Clínicas, Universidade Federal de Minas Gerais. METHODS: The study included 333 patients, of both genders and mean age 45 ± 15 years, who underwent thyroidectomy between 2000 and 2005. Total calcium, phosphorus and magnesium were measured in the blood preoperatively and 24 and 48 hours postoperatively. Ionic changes were evaluated according to the presence or absence of postoperative hypocalcemia. RESULTS: There were statistically significant drops in blood phosphorus levels 24 and 48 hours after thyroidectomy, compared with preoperative values, in the patients without hypocalcemia. In the patients who developed hypocalcemia, there was a significant drop in plasma phosphorus on the first postoperative day and an increase (also statistically significant) on the second day, in relation to preoperative phosphorus levels. A significant drop in postoperative magnesium was also observed on the first and second days after thyroidectomy in the patients with hypocalcemia, in relation to preoperative levels. In the patients without hypocalcemia, the drop in magnesium was significant on the first day, but there was no difference on the second day. CONCLUSION: Despite the postoperative changes, neither magnesium nor phosphorus ion levels had any role in post-thyroidectomy calcemia.


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