scholarly journals Calcium transport in intact human erthrocytes.

1976 ◽  
Vol 68 (1) ◽  
pp. 29-41 ◽  
Author(s):  
G Plishker ◽  
H J Gitelman
Keyword(s):  
Calcium Concentration ◽  
Calcium Uptake ◽  
Calcium Content ◽  
Ion Composition ◽  
Inhibitory Effects ◽  
Sodium Potassium ◽  
Tetramethylammonium Chloride ◽  
Low Concentrations ◽  
Net Uptake ◽  
External Calcium

Intact human erythrocytes can be readily loaded with calcium by incubation in hypersomotic media at alkaline pH. Erythrocyte calcium content increases from 15-20 to 120-150 nmol/g hemoglobin after incubation for 2 h at 20 degree C in a 400 mosmol/kg, pH 7.8 solution containing 100 mM sodium chloride, 90 mM tetramethylammonium chloride, 1 mM potassium chloride, and 10 mM calcium chloride. Calcium uptake is a time-dependent process that is associated with an augmented efflux of potassium. The ATP content in these cells remains at more than 60% of normal and is not affected by calcium. Calcium uptake is influenced by the cationic composition of the external media. The response to potassium is diphasic. With increasing potassium concentrations, the net accumulation of calcium initially increases, becoming maximal at 1 mM potassium, then diminishes, falling below basal levels at concentrations above 3 mM potassium. Ouabain inhibits the stimulatory effect of low concentrations of potassium. The inhibitory effects of higher concentrations of potassium are ouabain insensitive and independent of the external calcium concentration. Sodium also inhibits calcium uptake but this inhibition can be modified by altering the external concentration of calcium. The effux of calcium from loaded erythrocytes is not significantly altered by changes in osmolality, medium ion composition, or ouabain. It is concluded that hypertonicity increases the net uptake of calcium by increasing the influx of calcium and that some part of the sodium potassium transport system is involved in this influx process.

Invariance of Stoichiometry of the Sarcoplasmic Reticulum Calcium Pump at Physiological Calcium Concentrations – a Reevaluation

1985 ◽  
Vol 40 (7-8) ◽  
pp. 571-575 ◽  
Author(s):  
Wilhelm Hasselbach ◽  
Andrea Migala
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Level ◽  
Calcium Concentration ◽  
Calcium Uptake ◽  
Atp Hydrolysis ◽  
Calcium Pump ◽  
Oxalate Precipitation ◽  
Sarcoplasmic Reticulum Calcium ◽  
Internal Calcium ◽  
External Calcium

Abstract The decline of the transport ratio of the sarcoplasmic calcium pump observed in a recent study (A. results from the retardation of calcium oxalate precipitation at low calcium/protein ratios. The prevailing high internal calcium level supports a rapid calcium backflux and a compensatory ATP hydrolysis during net calcium uptake which reduces the transport ratio. Yet, the determined calcium back­ flux does not fully account for the decline of the transport ratio. A supposed modulation of the stoichiometry of the pump by external calcium (0.1 μм) is at variance with results of previous studies showing a constant transport ratio of two in the same calcium concentration range.

Effects of cadmium and zinc on calcium uptake in human red blood cells

1984 ◽  
Vol 247 (3) ◽  
pp. C143-C149 ◽  
Author(s):  
G. A. Plishker
Keyword(s):  
Red Blood Cells ◽  
Disulfide Bond ◽  
Blood Cells ◽  
Calcium Uptake ◽  
Sodium Potassium ◽  
Human Red Blood Cells ◽  
Low Concentrations ◽  
Influx Pathways ◽  
Extracellular Sodium ◽  
Passive Influx

Cadmium and zinc increased the accumulation of calcium in human red blood cells by increasing passive influx without enhancing the permeability to other ions. The effect of cadmium and zinc appeared specific to these metals, because barium, magnesium, cobalt, strontium, manganese, and nickel had no effect. Changes in calcium uptake by extracellular sodium, potassium, and pH were not altered by zinc and cadmium. Inhibition of calcium uptake by quinine, oligomycin, and iodoacetate was not affected by cadmium or zinc. These results suggest that cadmium and zinc increase calcium movement through normal influx pathways. Cadmium and zinc acted synergistically apparently by different mechanisms. Zinc and cadmium differentially affected calcium uptake in different extracellular calcium concentrations. The cadmium effect was increased by low concentrations of 2-mercaptoethanol and above pH 8.0, while the zinc effect was less sensitive to these factors. These findings suggest that the cadmium effect involves a disulfide bond between cysteinyl residues and the zinc effect involves a different site.

Role of calcium in acute stimulated release of prolactin from neoplastic GH3 cells

1981 ◽  
Vol 240 (6) ◽  
pp. E705-E711
Author(s):  
C. M. Moriarty ◽  
M. P. Leuschen
Keyword(s):  
Intracellular Calcium ◽  
Calcium Uptake ◽  
Calcium Content ◽  
Secretory Activity ◽  
Gh3 Cells ◽  
Free Medium ◽  
Cellular Calcium ◽  
Sensitive Electrode ◽  
External Calcium

Using a calcium-sensitive electrode to monitor calcium movements, we found that neoplastic GH3 cells experienced a net accumulation of calcium when exposed to elevated (50 mM) K+. Acute prolactin (PRL) release was also stimulated under these conditions. Both calcium uptake and PRL release could be blocked by the calcium antagonist methoxyverapamil (D-600). Thyrotropin-releasing hormone (TRH) also stimulated PRL release but had no effect on cellular calcium accumulation. Likewise, D-600 had no effect on TRH-induced PRL release. Such results indicate that enhanced secretory activity does not require an increase in intracellular calcium content. The observation that secretagogues do not stimulate PRL release in the absence of extracellular calcium was investigated. When GH3 cells were placed in a Ca-free medium, they underwent a prompt and sustained loss of cellular calcium. The loss of such intracellular calcium could be blocked with D-600. We conclude that the inability of TRH to stimulate the release of PRL in Ca-free medium is due to the loss of intracellular calcium and not to the absence of external calcium per se.

scholarly journals POTASSIUM MOVEMENT IN RELATION TO NERVE ACTIVITY

1951 ◽  
Vol 34 (6) ◽  
pp. 795-807 ◽  
Author(s):  
Abraham M. Shanes
Keyword(s):  
Time Constant ◽  
Calcium Concentration ◽  
Sea Water ◽  
Calcium Content ◽  
Squid Axon ◽  
Nerve Activity ◽  
Potassium Accumulation ◽  
Low Concentrations ◽  
Order Of Magnitude ◽  
Wet Weight

The depolarization of crab nerve during repetitive stimulation is unaffected by the presence of glucose or by an increase in the calcium content of the medium. It is increased in both amplitude and rate by veratrine; in the presence of this alkaloid mixture the rate but not the magnitude of the depolarization is increased by an elevation in the calcium concentration. Repolarization following stimulation is unaltered by glucose and accelerated by a greater calcium concentration. Veratrine increases both the amplitude and the time constant of repolarization; its effect on the time constant is counteracted by an elevation of the calcium in the medium. Potassium released during stimulation and its reabsorption following activity have been observed by analyses of small volumes of sea water in contact with crab nerve. Under the conditions employed 3 x 10–8 µM potassium is liberated per impulse per gm. wet weight of nerve. This loss is increased by low concentrations of veratrine, which also increase the amount reabsorbed during recovery. The depletion of potassium from the medium is appreciably less if the potassium previously released during activity has not been removed. Inexcitability resulting from anoxia can be washed away with oxygen-free solution—rapidly and completely in the case of the squid axon, slowly and incompletely in crab nerve. The potassium shifts are in the proper direction and of the correct order of magnitude to account for the negative and positive after-potentials in terms of potassium accumulation or depletion in the extracellular space.

scholarly journals Effects of ovine prolactin on calcium uptake and distribution in Oreochromis mossambicus

1986 ◽  
Vol 250 (2) ◽  
pp. R161-R166 ◽  
Author(s):  
G. Flik ◽  
J. C. Fenwick ◽  
Z. Kolar ◽  
N. Mayer-Gostan ◽  
S. E. Wendelar Bonga
Keyword(s):  
Uptake Rate ◽  
Calcium Uptake ◽  
Bone Mineralization ◽  
Calcium Content ◽  
Oreochromis Mossambicus ◽  
Whole Body ◽  
Bone Calcium ◽  
Net Uptake ◽  
Ovine Prolactin ◽  
Calcium Pool

Ovine prolactin stimulated the net uptake rate of Ca2+ from the water by 96%, produced frank hypercalcemia, and increased total bone calcium content in fed rapidly growing freshwater male tilapia, Oreochromis mossambicus. It did not, however, alter the size of the readily exchangeable bone calcium pool. The increase in calcium accumulation resulted from an increase in whole-body Ca2+ influx and a decrease in Ca2+ efflux. It is concluded that prolactin exerts an important control over Ca2+ exchange between the fish and its environment and that through its hypercalcemic action prolactin indirectly facilitates bone mineralization.

Prescription of Calcium Concentration and Pth Control

1996 ◽  
Vol 16 (1_suppl) ◽  
pp. 300-305 ◽  
Author(s):  
Eberhard Ritz ◽  
Jutta Passlick-Deetjen ◽  
Martin Zeier ◽  
Adam Stefanski
Keyword(s):  
Calcium Concentration ◽  
Calcium Uptake ◽  
Calcium Content ◽  
Phosphate Binders ◽  
Calcium Balance ◽  
Frequent Episodes ◽  
Prospective Trials ◽  
Term Maintenance ◽  
Stimulation Of

The use of calcium-containing oral phosphate binders, introduced in an effort to avoid aluminum-containing compounds, has led to more frequent episodes of hypercalcemia. This prompted the introduction of continuous ambulatory peritoneal dialysis (CAPD) solutions with diminished calcium content. The problems raised by such solutions included stimulation of parathyroid hormone (PTH) secretion and long-term maintenance of calcium balance. Some of these issues can today be answered on the basis of controlled prospective trials. Variability of the rate of intestinal calcium uptake of bone turnover, of baseline parathyroid activity, and other factors make it necessary to individualize the indication for the use of CAPD solutions with low calcium content.

scholarly journals Calcium uptake by mitochondria isolated from muskrat and guinea pig hearts

1991 ◽  
Vol 157 (1) ◽  
pp. 133-142
Author(s):  
T. A. McKean
Keyword(s):  
Guinea Pig ◽  
Calcium Concentration ◽  
Calcium Uptake ◽  
Membrane Damage ◽  
Indirect Measurements ◽  
45Ca Uptake ◽  
Hypoxia Ischemia ◽  
Interfibrillar Mitochondria ◽  
External Calcium

Subsarcolemmal and interfibrillar mitochondria were isolated from the hearts of the diving muskrat and non-diving guinea pig and direct and indirect measurements of calcium uptake were examined in vitro. The calcium-stimulated respiration rate and 45Ca uptake were measured and found to be greater in muskrat than in guinea pig mitochondria. Muskrat mitochondria were able to endure a greater external calcium concentration than guinea pig mitochondria before exhibiting indications of inner membrane damage. Calcium uptake by muskrat heart mitochondria was inhibited more by 1 mmoll-1 MgCl2 than was uptake by guinea pig mitochondria. No differences were detected between the interfibrillar and subsarcolemmal populations of mitochondria within species. An increased ability to sequester calcium by mitochondria without causing them damage may aid an animal during recovery from hypoxia, ischemia or acidosis.

Calcium Regulation in the Freshwater Mollusc Limnaea Stagnalis (L.) (Gastropoda: Pulmonata)

1971 ◽  
Vol 54 (3) ◽  
pp. 609-620 ◽  
Author(s):  
PETER GREENAWAY
Keyword(s):  
Calcium Concentration ◽  
Calcium Uptake ◽  
Calcium Regulation ◽  
Fresh Tissue ◽  
Blood Calcium ◽  
Freshwater Mollusc ◽  
Net Uptake ◽  
Tissue Calcium ◽  
Limnaea Stagnalis ◽  
Calcium Loss

1. Three major calcium compartments have been identified in L. stagnalis: the shell, the blood and the fresh tissues. 2. The distribution of 45Ca, absorbed from the medium, in the tissues of L. stagnalis has been studied. Absorbed calcium appears first in the blood and then in the shell and other tissues. 3. 30% of the total fresh tissue calcium and about 20% of mantle calcium exchanges with blood calcium. A continual exchange between shell and blood calcium occurs. 4. During net calcium loss from L. stagnalis a net movement of calcium from shell to blood occurs at a rate similar to the rate of net loss. During net calcium uptake, the reverse movement from blood to shell at a rate similar to the rate of net uptake occurs. 5. A simple mechanism which might account for the control of blood calcium concentration has been proposed.

The Effects of Manganese on the Rabbit Anterior Mesenteric–Portal Vein

1972 ◽  
Vol 50 (4) ◽  
pp. 300-309 ◽  
Author(s):  
G. A. Collins ◽  
M. C. Sutter ◽  
J. C. Teiser
Keyword(s):  
Portal Vein ◽  
Calcium Concentration ◽  
Calcium Influx ◽  
Extracellular Fluid ◽  
Inhibitory Effects ◽  
Competitive Kinetics ◽  
Spontaneous Action ◽  
Spontaneous Action Potentials ◽  
Tonic Phase ◽  
External Calcium

The effects of manganese and lanthanum were tested on the contractile responses of the rabbit anterior mesenteric–portal vein (A.M.V.). Since these ions have been shown to block calcium fluxes in other tissues, examining their effects may give information concerning the importance of calcium influx for contractions of the A.M.V. The effects of the two cations on the A.M.V. were found to be similar except that lanthanum was more potent and its inhibitory effects were not readily reversible. Spontaneous action potentials and their associated contractions were abolished by the addition of 0.5 mM Mn2+. This inhibition could be rapidly reversed by adding EDTA to chelate the manganese. Manganese inhibited the responses to all agonists tested (noradrenaline, histamine, serotonin, procaine, and KCl). The inhibition of responses to all agonists but procaine could be partially reversed by raising the external calcium concentration. The interaction between calcium and manganese follows competitive kinetics. Adding manganese during the tonic phase of a contraction evoked by 10−6 g/ml noradrenaline resulted in a relaxation to a decreased, but sustained, tension. The inhibitory effects of manganese add further evidence that an influx of calcium from the extracellular fluid is required for spontaneous activity and for both the initiation and maintenance of contractions to agonists in the rabbit A.M.V.

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

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