The effects of Ca2+ antagonists on Ca2+ accumulation by subcellular fractions of rat myometrium

1977 ◽  
Vol 55 (5) ◽  
pp. 1028-1032 ◽  
Author(s):  
D. J. Crankshaw ◽  
R. A. Janis ◽  
E. E. Daniel
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Membrane Fraction ◽  
Mitochondrial Fraction ◽  
Mechanisms Of Action ◽  
Subcellular Fractions ◽  
Rat Uterus ◽  
Pharmacological Agents ◽  
Contraction Coupling ◽  
Dose Levels

Several agents which antagonize or interact with Ca2+ in the excitation–contraction coupling of smooth muscle have been tested for their effects on Ca2+ accumulation by subcellular fractions of the rat uterus. Na+, but not K+, reduced the amount of Ca2+ that could be accumulated by the plasma membrane fraction (PM) and the endoplasmic reticular fraction (ER). Sr2+ considerably reduced Ca2+ accumulation by PM, ER, and the mitochondrial fraction; Ba2+ had a similar effect but was not as potent as Sr2+ La3+ at concentrations up to 10 mM was unable to block Ca2+ accumulation by PM and ER completely. The pharmacological agents D600, verapamil, and chlorpromazine all inhibited Ca2+ accumulation at dose levels much higher than those required to inhibit contractility, and were ineffective at lower doses. The action of Ca2+ antagonists is seen to be complex, involving interactions at different sites and on different processes. For a fuller understanding of their mechanisms of action further studies upon passive binding and on the release of Ca2+ from subcellular sites are required.

Angiotensinase activity and angiotensin receptor binding in guinea pig aorta

1977 ◽  
Vol 55 (3) ◽  
pp. 652-657 ◽  
Author(s):  
Patrick Le Morvan ◽  
Djuro Palaic ◽  
Dragana Ferguson
Keyword(s):  
Enzyme Activity ◽  
Plasma Membrane ◽  
Guinea Pig ◽  
Membrane Fraction ◽  
Binding Capacity ◽  
Specific Binding ◽  
Mitochondrial Fraction ◽  
Subcellular Fractions ◽  
Angiotensin Receptor ◽  
Plasma Membrane Fraction

The angiotensinase (EC 3.4.99.3) activity of the subcellular fractions of guinea pig aorta has been studied in relation to their [14C]angiotensin binding capacity. The enzyme activity occurs in the following decreasing order: supernatant > plasma membrane fraction > 105 000 × g pellet > mitochondrial fraction. The specific binding of [14C]angiotensin to these fractions follows the same pattern. Pretreatment of the subcellular fractions at 47 °C for 20 min was performed in an attempt to differentiate binding of angiotensin to the pharmacological receptor from binding to the destroying enzymes. This procedure decreased the angiotensinase activity in the plasma membrane fraction only whereas the specific binding of [14C]angiotensin to this fraction was not significantly decreased, suggesting that the plasma membrane angiotensinase is a thermolabile enzyme.

scholarly journals TNFα decreases mitochondrial movement in human airway smooth muscle

2017 ◽  
Vol 313 (1) ◽  
pp. L166-L176 ◽  
Author(s):  
Philippe Delmotte ◽  
Vanessa A. Zavaletta ◽  
Michael A. Thompson ◽  
Y. S. Prakash ◽  
Gary C. Sieck
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Airway Smooth Muscle ◽  
Hot Spots ◽  
Energy Coupling ◽  
Human Airway Smooth Muscle ◽  
Atp Production ◽  
Contraction Coupling ◽  
Mitochondrial Movement ◽  
Agonist Stimulation

In airway smooth muscle (ASM) cells, excitation-contraction coupling is accomplished via a cascade of events that connect an elevation of cytosolic Ca2+ concentration ([Ca2+]cyt) with cross-bridge attachment and ATP-consuming mechanical work. Excitation-energy coupling is mediated by linkage of the elevation of [Ca2+]cyt to an increase in mitochondrial Ca2+ concentration, which in turn stimulates ATP production. Proximity of mitochondria to the sarcoplasmic reticulum (SR) and plasma membrane is thought to be an important mechanism to facilitate mitochondrial Ca2+ uptake. In this regard, mitochondrial movement in ASM cells may be key in establishing proximity. Mitochondria also move where ATP or Ca2+ buffering is needed. Mitochondrial movement is mediated through interactions with the Miro-Milton molecular complex, which couples mitochondria to kinesin motors at microtubules. We examined mitochondrial movement in human ASM cells and hypothesized that, at basal [Ca2+]cyt levels, mitochondrial movement is necessary to establish proximity of mitochondria to the SR and that, during the transient increase in [Ca2+]cyt induced by agonist stimulation, mitochondrial movement is reduced, thereby promoting transient mitochondrial Ca2+ uptake. We further hypothesized that airway inflammation disrupts basal mitochondrial movement via a reduction in Miro and Milton expression, thereby disrupting the ability of mitochondria to establish proximity to the SR and, thus, reducing transient mitochondrial Ca2+ uptake during agonist activation. The reduced proximity of mitochondria to the SR may affect establishment of transient “hot spots” of higher [Ca2+]cyt at the sites of SR Ca2+ release that are necessary for mitochondrial Ca2+ uptake via the mitochondrial Ca2+ uniporter.

scholarly journals Enzyme activity and composition of myelin and subcellular fractions in the developing rat brain

1969 ◽  
Vol 115 (5) ◽  
pp. 1051-1062 ◽  
Author(s):  
N. L. Banik ◽  
A. N. Davison
Keyword(s):  
Enzyme Activity ◽  
Plasma Membrane ◽  
Rat Brain ◽  
Membrane Fraction ◽  
Subcellular Fractions ◽  
Aminopeptidase Activity ◽  
Adult Rat ◽  
Adult Rat Brain ◽  
Developing Rat ◽  
The Brain

1. Subcellular fractions and myelin were isolated from developing and adult rat brain. 2. Measurements of chemical composition and enzyme activities indicate the presence of a second myelin-like fraction mainly in the brain of developing rats. 3. This membrane fraction has a different lipid composition from myelin, but resembles myelin in its content of phosphohydrolase and aminopeptidase activity. 4. It is suggested that the second myelin-like fraction may be a submicrosomal contaminant or it may be derived from oligodendroglial plasma membrane during myelinogenesis.

scholarly journals Inhibitory antibodies to plasmalemmal Ca2+-transporting ATPases. Their use in subcellular localization of (Ca2+ + Mg2+)-dependent ATPase activity in smooth muscle

1985 ◽  
Vol 231 (3) ◽  
pp. 737-742 ◽  
Author(s):  
J Verbist ◽  
F Wuytack ◽  
L Raeymaekers ◽  
R Casteels
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Muscle ◽  
Plasma Membrane ◽  
Atpase Activity ◽  
Membrane Fraction ◽  
Transport Atpase ◽  
Calmodulin Binding ◽  
Dependent Atpase ◽  
Inhibitory Antibodies ◽  
Stimulation Of

Antibodies directed against the purified calmodulin-binding (Ca2+ + Mg2+)-ATPase [(Ca2+ + Mg2+)-dependent ATPase] from pig erythrocytes and from smooth muscle of pig stomach (antral part) were raised in rabbits. Both the IgGs against the erythrocyte (Ca2+ + Mg2+)-ATPase and against the smooth-muscle (Ca2+ + Mg2+)-ATPase inhibited the activity of the purified calmodulin-binding (Ca2+ + Mg2+)-ATPase from smooth muscle. Up to 85% of the total (Ca2+ + Mg2+)-ATPase activity in a preparation of KCl-extracted smooth-muscle membranes was inhibited by these antibodies. The (Ca2+ + Mg2+)-ATPase activity and the Ca2+ uptake in a plasma-membrane-enriched fraction from this smooth muscle were inhibited to the same extent, whereas in an endoplasmic-reticulum-enriched membrane fraction the (Ca2+ + Mg2+)-ATPase activity was inhibited by only 25% and no effect was observed on the oxalate-stimulated Ca2+ uptake. This supports the hypothesis that, in pig stomach smooth muscle, two separate types of Ca2+-transport ATPase exist: a calmodulin-binding ATPase located in the plasma membrane and a calmodulin-independent one present in the endoplasmic reticulum. The antibodies did not affect the stimulation of the (Ca2+ + Mg2+)-ATPase activity by calmodulin.

scholarly journals The biosynthesis of brain gangliosides. Separation of membranes with different ratios of ganglioside sialylating activity to gangliosides

1977 ◽  
Vol 168 (3) ◽  
pp. 325-332 ◽  
Author(s):  
C A Landa ◽  
H J F Maccioni ◽  
A Arce ◽  
R Caputto
Keyword(s):  
Membrane Fraction ◽  
Time Course ◽  
Mitochondrial Fraction ◽  
Subcellular Fractions ◽  
Synthetase Activity ◽  
Acetylneuraminic Acid ◽  
Mitochondrial Fractions ◽  
Brain Gangliosides

Brain subcellular fractions were analysed for ganglioside-sialylating activity by measuring the incorporation of N-[3H]acetylneuraminic acid from CMP-N-[3H]acetylneuraminic acid into endogenous ganglioside acceptors (endogenous incorporation) and into exogenous lactosyceramide (haematoside synthetase activity). The ratios of endogenous incorporation to gangliosides and of haematoside synthetase to gangliosides for the synaptosomal and mitochondrial fractions from a washed crude mitochondrial fraction were lower than those obtained for other membrane fractions. The differences appear to reflect intrinsic characteristics of each membrane fraction. The results of labelling in vitro and the time course of labelling of gangliosides of the different subcellular fractions in vivo after injection of N-[3H]acetylmannosamine are consistent with the possibility of a subcellular site for synthesis of gangliosides different from that of ganglioside deposition.

scholarly journals Isolation of a plasma-membrane fraction from gastric smooth muscle. Comparison of the calcium uptake with that in endoplasmic reticulum

1983 ◽  
Vol 210 (2) ◽  
pp. 315-322 ◽  
Author(s):  
L Raeymaekers ◽  
F Wuytack ◽  
J Eggermont ◽  
G De Schutter ◽  
R Casteels
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Muscle ◽  
Plasma Membrane ◽  
Membrane Fraction ◽  
Microsomal Fraction ◽  
Membrane Vesicles ◽  
Cholesterol Content ◽  
Sucrose Density Gradient ◽  
Plasma Membrane Vesicles ◽  
Plasma Membrane Fraction

1. A plasma-membrane fraction was isolated from the smooth muscle of the pig stomach by using differential and sucrose-density-gradient centrifugations. When the centrifugation was carried out after preloading the crude microsomal fraction with Ca2+ in the presence of oxalate, the contamination of the plasma-membrane fraction by endoplasmic reticulum was decreased and a fraction enriched in endoplasmic reticulum vesicles filled with calcium oxalate crystals was obtained. 2. The plasmalemmal and endoplasmic-reticulum membranes could be distinguished by differences in the activity of marker enzymes and in the cholesterol content and by their different permeability to oxalate and phosphate. Oxalate and phosphate stimulated the Ca2+ uptake in the endoplasmic reticulum much more than in the plasmalemmal vesicles. In the plasma-membrane vesicles 40 mM-phosphate was more effective for stimulating the Ca2+ uptake than was 5 mM-oxalate, but the reverse was seen in the endoplasmic reticulum. 3. The high cholesterol/phospholipid ratio of the crude microsomal fraction are of the majority of the vesicles present in the crude microsomal fraction are of plasmalemmal origin. 4. The Ca2+ pump of the plasmalemmal and endoplasmic-reticulum vesicles could be differentiated by their different sensitivities to calmodulin. However, the two Ca2+-transport ATPases did not differ by their sensitivity to vanadate nor by the energization of the Ca2+ transport by different nucleoside triphosphates.

Differences in the Lipid Distribution in Subcellular Fractions of Mouse Fibroblasts Derived from Logarithmic and Stationary Growth

1976 ◽  
Vol 31 (3-4) ◽  
pp. 179-185 ◽  
Author(s):  
Hans Peter Kulas ◽  
F. Alfred Anderer
Keyword(s):  
Plasma Membrane ◽  
Lipid Class ◽  
Growth Phase ◽  
Membrane Fraction ◽  
Stationary Growth Phase ◽  
Subcellular Fractions ◽  
Cell Populations ◽  
Growth Phases ◽  
Stationary Growth ◽  
Mouse Fibroblasts

Abstract The lipid class compositions of subcellular fractions of SV40-transformed mouse fibroblasts derived from the logarithmic and stationary growth phase were compared. Cell populations of the stationary growth phase showed a relative decrease of the protein content and an increase of triglycerides and alkoxydiglycerides which could be located in the non-sedimenting fraction and in the nuclei and mitochondria containing fraction, respectively. Furtheron, distinct shifts in the subcellular distribution of those lipid classes could be observed which exhibited no relative overall increase or decrease when the cells of both growth phases were compared. In the crude plasma membrane fraction the ratio “lipid class/protein” remained about constant with the exception of the phospholipids and alkoxydiglycerides.

scholarly journals Smooth Muscle Excitation-Contraction Coupling: a Role for Caveolae and Caveolins?

Physiology ◽  
2001 ◽  
Vol 16 (2) ◽  
pp. 61-65 ◽  
Author(s):  
Michael J. Taggart
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Muscle Contractility ◽  
Smooth Muscle Contractility ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Agonist Stimulation ◽  
Integral Protein ◽  
Protein Components ◽  
Stimulation Of

Agonist stimulation of smooth muscle contractility involves integration of many signal-transducing events from the plasma membrane to myofilaments in the cytoplasm. Recent evidence suggests an important role for membranous invaginations termed caveolae, and their integral protein components caveolins, in the coordination of extracellular contractile stimuli and intracellular effectors in smooth muscle.

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