Mg2+ and Mn2+ effects on membrane-bound and detergent-solubilized adenylate cyclase

1981 ◽  
Vol 59 (9) ◽  
pp. 748-756 ◽  
Author(s):  
George I. Drummond
Keyword(s):  
Skeletal Muscle ◽  
Adenylate Cyclase ◽  
Cardiac Muscle ◽  
Catalytic Site ◽  
Maximal Velocity ◽  
Regulatory Site ◽  
Muscle Enzyme ◽  
Membrane Bound ◽  
Stimulation Of

Mg2+ and Mn2+ stimulation of basal, F−, and guanyl-5′-yl imidodiphosphate (GPP(NH)P) stimulated adenylate cyclase in particulate and detergent-solubilized preparations of skeletal muscle, cardiac muscle, and erythrocytes was examined. Solubilization decreased the concentrations of Mg2+ required for half-maximal velocity and for saturation. Concentrations of Mn2+ required for saturation and for half-maximal velocity of particulate preparations was much lower than for Mg2+ and these values were not markedly reduced by solubilization. Particulate and soluble preparations were similarly stimulated by NaF and GPP(NH)P. Activation of the heart and skeletal muscle enzyme by NaF and GPP(NH)P greatly reduced the Mg2+ requirement; this was seen with both particulate and solubilized preparations. It is suggested that solubilization removes Mg2+ action at a regulatory site; MgATP and MnATP are both effective at the catalytic site, the latter producing higher Vmax.

Roles of extracellular and "trigger" calcium ions in excitation–contraction coupling in skeletal muscle

1982 ◽  
Vol 60 (4) ◽  
pp. 427-439 ◽  
Author(s):  
George B. Frank
Keyword(s):  
Skeletal Muscle ◽  
Experimental Technique ◽  
Calcium Ions ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
New Findings ◽  
Membrane Bound ◽  
Stimulation Of

The experimental observations leading to the development of the "trigger" calcium hypothesis of excitation–contraction (E–C) coupling in skeletal muscle are discussed. Also considered in some detail are the experimental technique problems which interfere with the demonstration of this role for calcium. New findings reported are observations showing that in a zero Ca2+ solution after a delay of about 6–10 min, there is a stimulation of Ca2+ efflux. This is of sufficient size, even in very small toe muscles, to restore the twitch which previously had been reduced in size in the zero Ca2+. In studies with isolated fibre preparations it was demonstrated that depolarization contractures required extracellular Ca2+ ions for E–C coupling whereas twitches could use membrane-bound "trigger" calcium ions. Thus in zero Ca2+ the contractures were eliminated in a few seconds but twitch elimination took a few minutes. Finally, the roles in E–C coupling played by "trigger" and extracellular Ca2+ ions are summarized and discussed.

scholarly journals Guanylate cyclase. Subcellular distribution in cardiac muscle, skeletal muscle, cerebral cortex and liver

1976 ◽  
Vol 157 (3) ◽  
pp. 705-712 ◽  
Author(s):  
P V Sulakhe ◽  
S J Sulakhe ◽  
N L Leung ◽  
P J St Louis ◽  
R A Hickie
Keyword(s):  
Skeletal Muscle ◽  
Cerebral Cortex ◽  
Adenylate Cyclase ◽  
Cardiac Muscle ◽  
Guanylate Cyclase ◽  
Plasma Membranes ◽  
Specific Activity ◽  
Frog Heart ◽  
Dependent Atpase ◽  
Absolute Requirement

1. Guanylate cyclase of every fraction studied showed an absolute requirement for Mn2+ ions for optimal activity; with Mg2+ or Ca2+ reaction was barely detectable. Triton X-100 stimulated the particulate enzyme much more than the supernatant enzyme and solubilized the particulate-enzyme activity. 2. Substantial amounts of guanylate cyclase were recovered with the washed particulate fractions of cardiac muscle (63-98%), skeletal muscle (77-93%), cerebral cortex (62-88%) and liver (60-75%) of various species. The supernatants of these tissues contained 7-38% of total activities. In frog heart, the bulk of guanylate cyclase was present in the supernatant fluid. 3. Plasma-membrane fractions contained 26, 21, 22 and 40% respectively of the total homogenate guanylate cyclase activities present in skeletal muscle (rabbit), cardiac muscle (guinea pig), liver (rat) and cerebral cortex (rat). In each case, the specific activity of this enzyme in plasma membranes showed a five- to ten-fold enrichment when compared with homogenate specific activity. 4. These results suggest that guanylate cyclase, like adenylate cyclase, and ouabain-sensitive Na+ + K+-dependent ATPase (adenosine triphosphatase), is associated with the surface membranes of cardiac muscle, skeletal muscle, liver and cerebral cortex; however, considerable activities are also present in the supernatant fractions of these tissues which contain very little adenylate cyclase or ouabain-sensitive Na+ + K+-dependent ATPase activities.

scholarly journals Sarco/endoplasmic reticulum Ca2+-ATPase isoforms: diverse responses to acidosis

1997 ◽  
Vol 321 (2) ◽  
pp. 545-550 ◽  
Author(s):  
Herman WOLOSKER ◽  
Joao B. T. ROCHA ◽  
Simone ENGELENDER ◽  
Rogerio PANIZZUTTI ◽  
Joari De MIRANDA ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Atp Hydrolysis ◽  
Blood Platelets ◽  
The Other ◽  
Maximal Velocity ◽  
Acidic Ph ◽  
Apparent Affinity ◽  
Maximal Activation ◽  
Kinetics Of

The effects of acidic pH on the kinetics of Ca2+-ATPase isoforms from intracellular membranes of skeletal muscle, cardiac muscle, cerebellum and blood platelets were studied. At neutral pH, all four Ca2+-ATPase isoforms exhibited similar Ca2+-concentration requirements for half-maximal rates of Ca2+ uptake and ATP hydrolysis. A decrease in the pH from 7.0 to 6.0 promoted a decrease in both the apparent affinity for Ca2+ [increasing half-maximal activation (K0.5)] and the maximal velocity (Vmax) of Ca2+ uptake. With skeletal muscle vesicles these effects were 5 to 10 times smaller than those observed with all the other isoforms. Acidification of the medium from pH 7.0 to 6.5 caused the release of Ca2+ from loaded vesicles and a decrease in the amount of Ca2+ retained by the vesicles at the steady state. With the vesicles derived from skeletal muscle these effects were smaller than for vesicles derived from other tissues. The rate of passive Ca2+ efflux from skeletal and cardiac muscle vesicles, loaded with Ca2+ and diluted in a medium containing none of the ligands of Ca2+-ATPase, was the same at pH 7.0 and 6.0. In contrast, the rate of Ca2+ efflux from cerebellar and platelet vesicles increased 2-fold after acidification of the medium. The effects of DMSO, Mg2+ with Pi and arsenate on the rate of Ca2+ efflux varied among the different preparations tested. The differences became more pronounced when the pH of the medium was decreased from 7.0 to 6.0. It is proposed that the kinetic differences among the Ca2+-ATPase isoforms may reflect different adaptations to cellular acidosis, such as that which occurs during ischaemia.

Stimulation of the slow calcium current in bullfrog skeletal muscle fibers by cAMP and cGMP

1993 ◽  
Vol 265 (1) ◽  
pp. C47-C53 ◽  
Author(s):  
T. G. Kokate ◽  
J. A. Heiny ◽  
N. Sperelakis
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Cyclic Nucleotides ◽  
Muscle Fibers ◽  
Cyclic Monophosphate ◽  
Current Voltage ◽  
Current Voltage Relationship ◽  
Camp And Cgmp ◽  
Voltage Relationship ◽  
Stimulation Of

The effects of adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) on slow calcium currents (ICa) were investigated using the Vaseline-gap voltage-clamp technique in bullfrog skeletal muscle cut fibers. Both cAMP and cGMP induced a pronounced increase in the amplitude of ICa when applied to the cut ends of fibers. Both cyclic nucleotides also decreased time to peak current at all membrane potentials. The current-voltage relationship was shifted toward more negative potentials by cAMP as well as cGMP. The potentiating effects of cAMP and cGMP on ICa were additive. 8-Bromo analogues of both nucleotides had similar effects on ICa. The beta-adrenergic agonist isoproterenol, applied extracellularly, also produced an increase in the amplitude of ICa and produced a leftward shift in the current-voltage relationship. These results suggest that both cAMP and cGMP modulate calcium slow channels in bullfrog skeletal muscle fibers, causing stimulation of the ICa. The effect of cyclic nucleotides on ICa in bullfrog skeletal muscle contrasts with that in mammalian cardiac muscle, in which the same nucleotides produce opposite effects on the slow ICa, i.e., in cardiac muscle cAMP stimulates, and cGMP inhibits, the slow ICa.

scholarly journals Theoretical analysis of the consequences of cyclic nucleotide phosphodiesterase negative co-operativity. Amplification and positive co-operativity of cyclic AMP accumulation

1980 ◽  
Vol 192 (1) ◽  
pp. 241-246 ◽  
Author(s):  
C Erneux ◽  
J M Boeynaems ◽  
J E Dumont
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Cyclic Nucleotide ◽  
Slight Variation ◽  
Maximal Velocity ◽  
Cyclic Nucleotide Phosphodiesterases ◽  
Accumulation Curve ◽  
Cyclic Amp Accumulation ◽  
Stimulation Of ◽  
Nucleotide Phosphodiesterases

Most tissues contain multiple forms of cyclic nucleotide phosphodiesterases (3′:5′-cyclic-nucleotide 5′ nucleotidohydrolase, EC 3.1.4.17). Consequently, in most, if not in all, tissues, substrate-velocity curves deviate from Michaelian kinetics and exhibit an apparent negative co-operativity. We have studied the possible theoretical consequences of this property on the quantitative features of cyclic AMP accumulation in response to activation of adenylate cyclase. Negative co-operativity of phosphodiesterases tends to generate a “positively co-operative” cyclic AMP accumulation curve. It amplifies the stimulation of cyclic AMP accumulation as compared with the stimulation of cyclic AMP synthesis. It enhances the sensitivity of cyclic AMP accumulation to slight variation of phosphodiesterase maximal velocity. It tends to shift the cyclic AMP accumulation curve to higher concentrations of stimulator as compared with the adenylate cyclase activation curve. This accounts for much of the data in the literature of hormonal effects on phosphodiesterase activity. It shows that the characteristics of cyclic nucleotide phosphodiesterases are as important as those of adenylate cyclase in determining the response of the system.

The Increased Sensitivity of Platelets to Prostacyclin in Marathon Runners

1984 ◽  
Vol 51 (03) ◽  
pp. 385-387 ◽  
Author(s):  
Clive J Dix ◽  
David G Hassall ◽  
K Richard Bruckdorfer
Keyword(s):  
Cardiovascular Disease ◽  
Endothelial Cells ◽  
Platelet Aggregation ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Platelet Rich Plasma ◽  
Marathon Runners ◽  
Inhibition Of Platelet Aggregation ◽  
Increased Sensitivity ◽  
Membrane Bound

SummaryPlatelet-rich plasma was obtained 24 hr after the race ended from athletes who ran in the London marathon. The platelets were only marginally less sensitive to adrenaline than were those of non-runners using conventional aggregation tests. However, the runners’ platelets were much more sensitive to inhibition by prostacyclin, a prostaglandin synthesized by endothelial cells. It appeared that this effect was due to a greater activity in the platelets of the membrane-bound adenylate cyclase enzyme which generates intracellular cyclic AMP. Cyclic AMP production is known to be stimulated by prostacyclin and to cause the inhibition of platelet aggregation. The results indicate another possible protective effect of exercise against cardiovascular disease which is independent of the known changes in lipoprotein concentrations previously observed in athletes.

Skeletal and cardiac muscle protein turnover during cold acclimation in young rats

2000 ◽  
Vol 278 (3) ◽  
pp. R705-R711 ◽  
Author(s):  
T. A. McAllister ◽  
J. R. Thompson ◽  
S. E. Samuels
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Cardiac Muscle ◽  
Cold Acclimation ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Turnover ◽  
Protein Mass ◽  
The Absolute

The effect of long-term cold exposure on skeletal and cardiac muscle protein turnover was investigated in young growing animals. Two groups of 36 male 28-day-old rats were maintained at either 5°C (cold) or 25°C (control). Rates of protein synthesis and degradation were measured in vivo on days 5, 10, 15, and 20. Protein mass by day 20 was ∼28% lower in skeletal muscle (gastrocnemius and soleus) and ∼24% higher in heart in cold compared with control rats ( P < 0.05). In skeletal muscle, the fractional rates of protein synthesis ( k syn) and degradation ( k deg) were not significantly different between cold and control rats, although k syn was lower (approximately −26%) in cold rats on day 5; consequent to the lower protein mass, the absolute rates of protein synthesis (approximately −21%; P < 0.05) and degradation (approximately −13%; P < 0.1) were lower in cold compared with control rats. In heart, overall, k syn(approximately +12%; P < 0.1) and k deg(approximately +22%; P < 0.05) were higher in cold compared with control rats; consequently, the absolute rates of synthesis (approximately +44%) and degradation (approximately +54%) were higher in cold compared with control rats ( P < 0.05). Plasma triiodothyronine concentration was higher ( P < 0.05) in cold compared with control rats. These data indicate that long-term cold acclimation in skeletal muscle is associated with the establishment of a new homeostasis in protein turnover with decreased protein mass and normal fractional rates of protein turnover. In heart, unlike skeletal muscle, rates of protein turnover did not appear to immediately return to normal as increased rates of protein turnover were observed beyond day 5. These data also indicate that increased rates of protein turnover in skeletal muscle are unlikely to contribute to increased metabolic heat production during cold acclimation.

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