scholarly journals Changes in Ca-ATPase Activity and Ca Uptake Rate of Erythrocytes of the Stroke-Prone SHR in Relation to Aging

1979 ◽  
Vol 20 (5) ◽  
pp. 748-748
Author(s):  
Hideaki Higashino ◽  
Takao Yanagawa ◽  
Noriyoshi Kazimoto ◽  
Aritomo Suzuki
Keyword(s):  
Atpase Activity ◽  
Uptake Rate ◽  
Ca Uptake

scholarly journals Changes in Ca-ATPase Activity and Ca Uptake Rate of Heart Muscle SR of the Stroke-Prone SHR in Relation to Aging

1979 ◽  
Vol 20 (5) ◽  
pp. 699-699
Author(s):  
Hideaki Higashino ◽  
Takao Yanagawa ◽  
Aritomo Suzuki
Keyword(s):  
Atpase Activity ◽  
Uptake Rate ◽  
Heart Muscle ◽  
Ca Uptake

Anion-dependent Mg2+ influx and a role for a vacuolar H+-ATPase in sheep ruminal epithelial cells

2003 ◽  
Vol 285 (1) ◽  
pp. G45-G53 ◽  
Author(s):  
Monika Schweigel ◽  
Holger Martens
Keyword(s):  
Epithelial Cells ◽  
Atpase Activity ◽  
Primary Culture ◽  
Intracellular Ph ◽  
Uptake Rate ◽  
Ruminal Fermentation ◽  
Fermentation Products ◽  
Fluorescence Techniques ◽  
Transport Inhibitors ◽  
Stimulation Of

The K+-insensitive component of Mg2+ influx in primary culture of ruminal epithelial cells (REC) was examined by means of fluorescence techniques. The effects of extracellular anions, ruminal fermentation products, and transport inhibitors on the intracellular free Mg2+ concentration ([Mg2+]i), Mg2+ uptake, and intracellular pH were determined. Under control conditions (HEPES-buffered high-NaCl medium), the [Mg2+]i of REC increased from 0.56 ± 0.14 to 0.76 ± 0.06 mM, corresponding to a Mg2+ uptake rate of 15 μM/min. Exposure to butyrate did not affect Mg2+ uptake, but it was stimulated (by 84 ± 19%) in the presence of [Formula: see text]. In contrast, Mg2+ uptake was strongly diminished if REC were suspended in [Formula: see text]-buffered high-KCl medium (22.3 ± 4 μM/min) rather than in HEPES-buffered KCl medium (37.5 ± 6 μM/min). After switching from high- to low-Cl– solution, [Mg2+]i was reduced from 0.64 ± 0.09 to 0.32 ± 0.16 mM and the [Formula: see text]-stimulated Mg2+ uptake was completely inhibited. Bumetanide and furosemide blocked the rate of Mg2+ uptake by 64 and 40%, respectively. Specific blockers of vacuolar H+-ATPase reduced the [Mg2+]i (36%) and Mg2+ influx (38%) into REC. We interpret this data to mean that the K+-insensitive Mg2+ influx into REC is mediated by a cotransport of Mg2+ and Cl– and is energized by an H+-ATPase. The stimulation of Mg2+ transport by ruminal fermentation products may result from a modulation of the H+-ATPase activity.

scholarly journals Ca2+-ATPase activity and Ca2+ uptake by sarcoplasmic reticulum in fish heart: effects of thermal acclimation.

1998 ◽  
Vol 201 (4) ◽  
pp. 525-532 ◽  
Author(s):  
E Aho ◽  
M Vornanen
Keyword(s):  
Atpase Activity ◽  
Uptake Rate ◽  
Teleost Fish ◽  
Crucian Carp ◽  
Thermal Acclimation ◽  
The Body ◽  
Newborn Rat ◽  
Fish Heart ◽  
Adult Rat ◽  
Uptake Velocity

This study was designed to compare the activities of sarcoplasmic (SR) Ca2+-ATPase and Ca2+ uptake in fish and mammalian hearts and to determine whether thermal acclimation has any effect on the function of the cardiac SR in fish. To this end, we measured thapsigargin-sensitive Ca2+-ATPase activity and thapsigargin-inhibitable Ca2+ uptake velocity in crude cardiac homogenates of newborn and adult rats and of two teleost fish (crucian carp and rainbow trout) acclimated to low (4 degrees C) and high (17 degrees C and 24 degrees C for trout and carp, respectively) ambient temperatures. The TG-sensitive Ca2+-ATPase activity was highest in adult rat, and the corresponding activities of cold-acclimated trout, warm-acclimated trout, warm-acclimated carp, cold-acclimated carp and newborn rat were 76, 58, 43, 28 and 23 %, respectively, of that of the adult rat at 25 degrees C. SR Ca2+ uptake velocity, measured using Fura-2 at room temperature (approximately 22 degrees C), was highest in cold-acclimated trout, and the values for adult rat, warm-acclimated trout, newborn rat, warm-acclimated carp and cold-acclimated carp were 93, 56, 24, 21 and 14 % of the uptake velocity of cold-acclimated trout, respectively. When corrected to the body temperature of the animal, the relative rates of SR Ca2+ uptake were 100, 26, 19, 18, 11 and 2 % for adult rat, newborn rat, cold-acclimated trout, warm-acclimated trout, warm-acclimated carp and cold-acclimated carp, respectively. These findings show that SR Ca2+ uptake is slower in fish than in mammalian hearts and that marked species-specific differences exist among teleost fish in this respect. Furthermore, acclimation to cold increases the Ca2+ uptake rate of trout cardiac SR (complete thermal compensation) but decreases the SR Ca2+ uptake rate of crucian carp heart. This difference in acclimation response probably reflects the different activity patterns of the two species in their natural habitat during the cold season.

scholarly journals Ca2+-sequestering smooth endoplasmic reticulum in an invertebrate photoreceptor. II. Its properties as revealed by microphotometric measurements.

1982 ◽  
Vol 93 (3) ◽  
pp. 849-859 ◽  
Author(s):  
B Walz
Keyword(s):  
Endoplasmic Reticulum ◽  
Uptake Rate ◽  
Smooth Endoplasmic Reticulum ◽  
High Specificity ◽  
Optical Signal ◽  
Uptake Mechanism ◽  
Intact Cells ◽  
Rate Of Increase ◽  
Ca Uptake ◽  
Ca Oxalate

Microphotometric measurements are used to investigate the functional properties of Ca2+-sequestering smooth endoplasmic reticulum (SER) in leech photoreceptors. 10-30 intact cells are mounted in a perfusion chamber, placed between crossed polarizers in a microphotometer, and permeabilized by saponin treatment. Subsequent perfusion with solutions containing Ca2+, MgATP, and oxalate leads to Ca uptake by SER. When the solubility product of Ca-oxalate is exceeded in the SER, birefringent Ca-oxalate precipitates form in the cisternae, leading to a large increase in the optical signal recorded from the preparation. The rate of increase in light intensity is used to measure the rate of Ca uptake. Ca uptake rate is linear with time over much of its course, can be switched on/off by the addition/withdrawal of Ca2+, ATP, or oxalate to/from the medium, and is inhibited by mersalyl and tetracaine. The Ca uptake mechanism has a high specificity for MgATP (KM,MgATP is approximately 0.8 mM). Uptake rates observed with dATP, GTP, UTP, ITP, and CTP are only 20-30% of the rate measured in ATP. The Ca pump has a high affinity for Ca2+ ions: the threshold for activation of the pump is approximately 5 x 10(-8) M, the apparent KM,Ca is approximately 4 x 10(-7) M. When Na+ or Li+ is substituted for K+, Ca uptake rate is decreased by 40-50%. The results show that the Ca2+-sequestering SER in leech photoreceptors shares some basic properties with skeletal muscle sarcoplasmic reticulum and supports the idea that certain subregions of the SER in invertebrate photoreceptors function as effective Ca2+ sinks/buffers close to the plasmalemma.

Prolonged exercise to fatigue in humans impairs skeletal muscle Na+-K+-ATPase activity, sarcoplasmic reticulum Ca2+ release, and Ca2+ uptake

2004 ◽  
Vol 97 (4) ◽  
pp. 1414-1423 ◽  
Author(s):  
James A. Leppik ◽  
Robert J. Aughey ◽  
Ivan Medved ◽  
Ian Fairweather ◽  
Michael F. Carey ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
G Protein ◽  
Uptake Rate ◽  
Prolonged Exercise ◽  
Transport Processes ◽  
Vastus Lateralis Muscle ◽  
Ouabain Binding ◽  
Exercise In Humans

Prolonged exhaustive submaximal exercise in humans induces marked metabolic changes, but little is known about effects on muscle Na+-K+-ATPase activity and sarcoplasmic reticulum Ca2+ regulation. We therefore investigated whether these processes were impaired during cycling exercise at 74.3 ± 1.2% maximal O2 uptake (mean ± SE) continued until fatigue in eight healthy subjects (maximal O2 uptake of 3.93 ± 0.69 l/min). A vastus lateralis muscle biopsy was taken at rest, at 10 and 45 min of exercise, and at fatigue. Muscle was analyzed for in vitro Na+-K+-ATPase activity [maximal K+-stimulated 3- O-methylfluorescein phosphatase (3- O-MFPase) activity], Na+-K+-ATPase content ([3H]ouabain binding sites), sarcoplasmic reticulum Ca2+ release rate induced by 4 chloro- m-cresol, and Ca2+ uptake rate. Cycling time to fatigue was 72.18 ± 6.46 min. Muscle 3- O-MFPase activity (nmol·min−1·g protein−1) fell from rest by 6.6 ± 2.1% at 10 min ( P < 0.05), by 10.7 ± 2.3% at 45 min ( P < 0.01), and by 12.6 ± 1.6% at fatigue ( P < 0.01), whereas 3[H]ouabain binding site content was unchanged. Ca2+ release (mmol·min−1·g protein−1) declined from rest by 10.0 ± 3.8% at 45 min ( P < 0.05) and by 17.9 ± 4.1% at fatigue ( P < 0.01), whereas Ca2+ uptake rate fell from rest by 23.8 ± 12.2% at fatigue ( P = 0.05). However, the decline in muscle 3- O-MFPase activity, Ca2+ uptake, and Ca2+ release were variable and not significantly correlated with time to fatigue. Thus prolonged exhaustive exercise impaired each of the maximal in vitro Na+-K+-ATPase activity, Ca2+ release, and Ca2+ uptake rates. This suggests that acutely downregulated muscle Na+, K+, and Ca2+ transport processes may be important factors in fatigue during prolonged exercise in humans.

scholarly journals The Mechanism of the Action of Caffeine on Sarcoplasmic Reticulum

1968 ◽  
Vol 52 (5) ◽  
pp. 760-772 ◽  
Author(s):  
A. Weber
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Transport System ◽  
Turnover Rate ◽  
Atp Hydrolysis ◽  
Uptake System ◽  
Transport Atpase ◽  
Ca Uptake

Evidence is presented that caffeine does not act on the mitochondrial Ca uptake system and that its effect cannot be attributed to the accumulation of adenosine 3',5'-phosphate. Two distinct caffeine effects are described. At high ATP concentrations caffeine decreases the coupling between ATP hydrolysis and Ca inflow. It either inhibits inflow without any inhibition of the rate of ATP hydrolysis, or it stimulates the ATPase activity without stimulating Ca inflow. These high ATP concentrations (much higher than needed for the saturation of the transport ATPase) greatly reduce the control of the turnover rate of the transport system, by accumulated Ca. At low ATP concentrations when the transport system is under maximal control by accumulated Ca, caffeine inhibits the ATPase activity without affecting the rate of Ca inflow.

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