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O V Esyrev

Publications and source records attributed to O V Esyrev.

At least 19 recordsLinked to original sources
PubMed1992

[The role of a GTP-binding protein in coupling of a muscarinic cholinergic receptor and Na,K-ATPase in myocardial sarcolemma].

The effects of the cholinergic agonist carbachol (Cch) and guanine nucleotides on the Na,K-ATPase and K-dependent p-nitrophenylphosphatase (K-p-NPPase) activities in rabbit and dog myocardial sarcolemma vesicles in the presence of the pore-forming antibiotic alamethicin (20 micrograms/ml), was studied. Cch (0.01-100 microM) inhibited the both enzymatic activities by 40-45% (IC50 = 0.3-0.5 microM) only after addition of GTP (50 microM) or its analogs: GTP gamma S (0.1-1.0 microM) and Gpp(NH)p (10 microM). The muscarinic acetylcholine receptor (mAchR) antagonist atropine (10 microM) blocked the effect of Cch. GTP gamma S alone produced a concentration-dependent decrease in the both Na,K-ATPase and K-p-NPPase activities by 40-45% (IC50 = 1-2 microM) with a lag period of about 3 minutes; this lag disappeared in the presence of the agonist. The GDP analog GDP beta S (0.01-100 microM) neither affected these activities nor promoted the inhibiting effect of Cch. Pretreatment of sarcolemmal vesicles with 20 micrograms/ml of pertussis toxin in the presence of 100 microM NAD abolished the inhibiting effect of Cch on the Na,K-ATPase and phosphatase activities. Under these conditions pertussis toxin catalyzed the ADP-ribosylation of alpha-subunits of the inhibitory GTP-binding protein (G1) which were identified immunochemically as alpha i2, alpha i3 and, possibly, alpha i1. The data obtained testify to the involvement of G1 in the mAchR-mediated inhibition of myocardial sarcolemmal Na,K-ATPase as well as in the signal transduction from the receptor to the enzyme.

Animals↗
PubMed1991

Vanadate inhibition of ATP and p-nitrophenyl phosphate hydrolysis in the fragmented sarcoplasmic reticulum.

The vanadate inhibition of the Ca(2+)-ATPase activity was analysed both in intact sarcoplasmic reticulum vesicles and in the presence of low concentrations of Tween 20, using ATP and p-nitrophenyl phosphate as substrates. The saturation of the internal low-affinity calcium-binding sites protects the enzyme against vanadate inhibition, because: (1) p-nitrophenyl phosphate hydrolysis is not inhibited by vanadate in intact vesicles, but inhibition developed after solubilization with detergents; (2) the vanadate inhibition of the p-nitrophenyl phosphate hydrolysis in solubilized preparations is prevented by free Ca2+ concentrations higher than 10(-3) M and vanadate competes with calcium (10(-5)-10(-3) M); and (3) the vanadate inhibition of ATP hydrolysis is decreased with an increase in vesicular Ca2+ concentration. The presence of magnesium ions is indispensable for the vanadate effect. The vanadate inhibition is non-competitive with respect to Mg-p-nitrophenyl phosphate and uncompetitive with respect to Mg-ATP. However, in the presence of dimethyl sulfoxide, which facilitates phosphorylation of the enzyme, the inhibition is converted to a competitive one with respect to a substrate. The results suggest, that in the process of enzyme operation vanadate interacts with the unliganded E form of Ca(2+)-ATPase, occupying probably an intermediate position between the E2 and E1 forms, with the formation of an E2 Van complex, that imposes the inhibition on the Ca(2+)-ATPase activity.

4-Nitrophenylphosphatase↗
PubMed1990

[Characteristics of ATPase activity in the sarcolemma of longitudinal and circular muscles of the canine ileum].

The subcellular fraction enriched in sarcolemmal vesicles was isolated from the longitudinal muscle (LM) and the circular muscle (CM) of the canine ileum by sucrose density gradient centrifugation. Treatment of the LM and CM membranes with sodium dodecylsulfate (0.2 mg/kg protein) led to a 3-fold increase in Na,K-ATPase activity (up to 24 and 39 mumol Pi/mg protein/h, respectively) and to a 90-95% inactivation of Mg-ATPase which was 2 and 8 times (for the CM and the LM, respectively) more active than Na,K-ATPase in the untreated sarcolemma. A specific inhibition of Na,K-ATPase activity by acetylcholine (Ach) and serotonin (ST) was observed which could de blocked in the presence of muscarinic and serotonin receptor antagonists. Sensitivity of the enzyme to ST was more than one order of magnitude higher than to Ach (IC50 = 10(-8) vs 1.2 x 10(-7) M). The inhibition of Na,K-ATPase activity by the neurotransmitters was more pronounced in the LM membranes (30-40%) than in the CM ones (10-20%). These data indicate that cell membranes of the LM and CM differ both in specific ATPase activities and the responsiveness of Na,K-ATPase to the receptor-mediated effects of Ach and ST.

Acetylcholine↗
PubMed1989

[The effect of neomycin on the contractile activity of the skeletal muscles in the frog].

Neomycin, a selective inhibitor of the phosphoinositide metabolism, depending on its concentration and the incubation time, depressed the K+-contractures and contractions of m. sartorius R. ridibunda caused by a single or a tetanic electrostimulation. In the experiments on m. rectus abdominis, neomycin inhibited the Ach- and oubaine contractures but not the K+ ones. The contractures of both muscles induced with caffeine did not change in presence of the above antibiotic. The data obtained suggest a participation of phosphoinositides contractions of skeletal muscles induced by excitation of the plasma membrane.

Acetylcholine↗
PubMed1987

[Changes in the activity and regulatory properties of Na, K-ATPase from the myocardial sarcolemma in total graded ischemia].

Na, K-ATPase activity of the rat and guinea-pig myocardial sarcolemma and its sensitivity to digoxin (DG) and carbamylcholine (CCh) were investigated during experimental ischemia. Ischemia was induced by the incubation of hearts in the air at 37 degrees C. This 15-, 30- and 45-min treatment led to a decrease in enzymatic activity which was similar in both animal species. Dose-related dependence of DG effect (10(-8)-10(-2) M) on sarcolemmal Na, K-ATPase activity of guinea-pig ischemic hearts did not differ from the control, whereas the rat enzyme sensitivity to glycosides rose with the progress of ischemia. CCh (10(-7)-10(-3) M) produced an inhibition of Na, K-ATPase activity which had reached 40% both in the rat and guinea-pig myocardial preparations. This effect was blocked by atropine (10(-6) M). The magnitude of enzyme responses to CCh declined depending on the duration of ischemia, with it being greater in guinea-pig sarcolemma than in rat membrane. The increased sensitivity of the rat Na, K-ATPase to CCh was also observed.

Animals↗
PubMed1984

[M-cholinoreceptor-mediated inhibition of Na, K-ATPase activity in the myocardial sarcolemma and intestinal smooth muscles by acetylcholine].

Acetylcholine (ACH) produced specific inhibition of Na, K-ATP-ase activity in sarcolemmic preparations of the frog heart (K0.5 = 1 microM), dog atria (K0,5 = 5 microM) and ventricles (K0.5 = 1 microM), and dog small intestinal smooth muscles (K0,5 = 0.5 microM). K0.5 is the concentration causing a half-maximal effect. Atropine (10(-7) = 10(-6) M) blocked the inhibitory effect of ACH. The preparations contained a considerable number of 3H-quinuclidinyl benzilate (3H-QNB) binding sites. Treatment of atrial sarcolemma with a mixture of digitonin and sodium cholate resulted in a substantial decrease in the number of 3H-QNB binding sites in the membrane, while Na,K-ATPase lost responsiveness to ACH. In the presence of 10 microM GTP there was a noticeable decrease in sensitivity of the enzyme to ACH. It is assumed that inhibition of Na, K-ATPase activity by acetylcholine is mediated by muscarinic receptor activation with the involvement in this process of GTP-binding proteins.

Acetylcholine↗
PubMed1984

[Cholinergic regulation of the Na, K-ATPase activity of the pig kidney].

Acetylcholine does not change the activity of Na, K-ATPase isolated from pig kidney. The enzyme is shown to have insignificant acetylcholinesterase activity. It is suggested that Na, K-ATPase sensitivity to acetylcholine disappears in the course of enzyme purification and that acetylcholinesterase activity is extrinsic.

Acetylcholine↗
PubMed1984

[Effect of caffeine and glycerin on the Ca transport system of sarcoplasmic reticulum fragments from frog skeletal muscles].

Parameters of the Ca2+-ion transport system by a fragmented sarcoplasmic reticulum isolated from phasic and tonic frog skeletal muscles were investigated under the action of caffeine or caffeine in combination with glycerol. No changes were observed in the Ca-transport system of a light fraction of the sarcoplasmic reticulum under the influence of caffeine and caffeine-glycerol combination. Caffeine reduced the value of Ca/ATP and enhanced the outflux of Ca2+-ions from membrane fragments of the caffeine-sensitive sarcoplasmic reticulum fraction of both the muscles; the combined effect of caffeine and glycerol was analogous to the action of caffeine applied alone. It is concluded that the potentiation of muscle contraction in the presence of glycerol is not due to the excess of Ca-release from the sarcoplasmic reticulum caused by this agent.

Absorption↗
PubMed1980

[Causative factor of Ca2+ transport reduction by sarcoplasmic reticulum fragments under the action of acetylcholine].

The uncoupling of Ca2+ uptake and ATP hydrolysis by acetylcholine (ACh) and choline has been demonstrated on fragmented sarcoplasmic reticulum (FSR) isolated from femoral muscles of Rana ridibunda. The uncoupling depends on the content of oxalate in the incubation medium. An increase in the Ca/ATP ratio caused by serum albumin observed at low oxalate concentrations is indicative of participation of free fatty acids in the uncoupling effect of ACh and choline. The effects of ACh and choline are especially well-pronounced in the case of FSR preparations pretreated with a fatty acid. ACh and choline have no effect on FSR from femoral muscles of Rana temporaria at all oxalate concentrations studied, which may be due to the absence of free fatty acids in these preparations. A pronounced uncoupling effect of ACh is observed after FSR incubation with a fatty acid; the activity of choline is pronounced in a much lesser degree. It is concluded that a decrease in the Ca/ATP ratio in the presence of ACh is due to the enhancement of the uncoupling effects of endogenous free fatty acids.

Acetylcholine↗
PubMed1979

[Effect of low-molecular nonelectrolytes and hypotonia on the contractile responses of frog sartorius muscles].

The potentiation of contractile responses during prolonged incubation of frog sartorius muscles in a conventional Ringer solution and in a calcium-free Ringer solution which contained 400 mM of urea, acetamide or ethylene glycol was observed when stimulation with single electric impulses and with caffeine was carried out. When the muscles were exposed to a hypotonic solution the reduction in the amplitude of caffeine contractures or their complete disappearance were registered, whereas the electrical stimulation of muscles in the same medium exerted an increase in the amplitude of contractile responses. The addition of 400 mM glycerol to the hypotonic solution caused an increase in the amplitude of contractions under both types of stimulation.

Acetamides↗
PubMed1978

[Acetylcholine induced reciprocal changes in the Na, K-ATPase and acetylcholinesterase activity of nerve and membrane preparations of Na, K-ATF-azy].

ATPase and cholinesterase activities in the homogenate of the frog nerve and membrane Na,K-ATPase preparation of the bovine brain were investigated. Preliminary treatment of the nerve and the preparation by acetylcholine solution (10(-6)--10(-7) M) enhanced their Na,K-ATPase activity and reduced their cholinesterase activity. Possible mechanisms of this phenomenon are discussed.

Acetylcholine↗
PubMed1977

[Mechanism of potentiation of contractions after muslce loading with glycerin. II. Relationship between incubation conditions and obstructing the inflow of glycerin].

A study was made of the influence of glycerol loading on contraction responses of the m. sartorius upon stimulation in normal and calcium-free Reinger solutions by caffeine, tetanic electrostimulation and single electric impulses. It was determined that in the glycerol medium each type of stimulation caused contractility potentiation. Ca2+-ions proved to block the responses of potentiation. The data suggest that there should be a potentiation mechanism common to each type of stimulation.

Animals↗
PubMed1976

[Some properties of transport ATPases in functionally different muscles].

The properties of Ca-transporting system in sarcoplasmic reticulum membranes in fast and slow frog muscles as well as some properties of sarcolemma Na, K-ATPase of the same object were investigated. The rate of Ca2+ uptake, Ca-ATPase activity and Ca/ATP ratio for the reticulum of fast muscle demonstrated higher values than those for the reticulum of slow muscle. The rate of Ca2+ accumulation by the fragments of the rectus reticulum and Ca/ATP ratio were found to decrease under the influence of acetylcholine (0.05-5 mM). The transport system of the sartorius reticulum was found to be less sensitive to acetylcholine. The peak activity of Na, K-ATPase in femoral muscles of the frog occurred at 80 mM NaCl and 60 mM KCl, whereas in the rectus abdominal muscle it equalled 100 mM NaCl and 40 mM KCl. Thus, Na, K-ATPase activity in the slow muscle was predominantly higher than that in the mixed (femoral) muscles. If the sarcolemma preparations of the muscles of both types the inhibitory effect of acetylcholine on Na; K-ATPase was registered. The enzyme of slow muscles exhibited higher sensibility to acetylcholine.

Adenosine Triphosphatases↗
PubMed1976

[Effect of various metabolic poisons on the nature of contraction of the straight muscle of the abdomen of frog].

A slow decline of responses was obtained after acetylcholine and KCl-stimulation of musculus rectus abdominis of the lake frog in the presence of antymicin A (0.27 mcg/ml). Dinitrophenol (up to 6.7.10(-4) M) as well as antymicin A inhibited the muscle contractility, with the effect being reversible. Muscle contraction ensued the application of dinitrophenol in concentration more than 6.7.10(-4)M. Decurarization ability of dinitrophenol was established. Mechanisms of disruption of the excitation--contraction coupling due to metabolic inhibitors are discussed.

Abdominal Muscles↗