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Biomedical subjects

S N Orlov

Publications and source records attributed to S N Orlov.

At least 127 records · Page 7Linked to original sources
PubMed1987

[Erythrocyte membrane phosphorylation in rats with spontaneous hypertension as affected by protein kinase C activator].

A study of orthophosphate incorporation into erythrocyte membrane proteins and lipids of spontaneously-hypertensive rats (SHR) at incubation of erythrocytes with 32PO4 and that of erythrocyte ghosts with 32P-gamma-ATP showed basal phosphorylation of proteins as well as polyphosphoinositides of erythrocyte ghosts to be essentially increased in SHRs as compared to normotensive animals, the differences being eliminated by the addition of protein kinase C activator (4 beta-phorbol-12 beta-myristate-13 alpha-acetate, PMA). After PMA-stimulated protein phosphorylation most of the label was incorporated into proteins of Band 4.1. There was no difference in basal phosphorylation of membrane proteins in case of intact erythrocytes. Under PMA stimulation, most of the label was incorporated into proteins of band 4.1 similarly to labelling of erythrocyte ghosts and a significant increment of radioactivity could only be seen in the control animals.

Animals↗
PubMed1987

[Characteristics of Na+/H+ metabolism in the erythrocytes of rats with spontaneous hypertension].

The dependence of the rate of valinomycin-induced Na+/H+ erythrocyte metabolism on the extracellular K+ concentration has been investigated. It has been established that Na+/H+ metabolism in the erythrocytes of spontaneously hypertensive rats (SHR) is induced at higher [K+]o concentrations than in normotensive controls (WKY). The distinctions in the maximum rate of Na+/H+ metabolism were revealed only in SHR in pre-hypertensive stage (it was 20% lower than in WKY). It is suggested that the distinctions are determined by peculiarities of membrane cytoskeleton formation. The conclusion was confirmed in experiments on erythrocyte stability to orthovanadate effect.

Amiloride↗
PubMed1986

Investigation of membrane proteins in rat erythrocytes in spontaneous hypertension by means of spin-label technique.

It has been suggested that alterations in cell membrane proteins may play a role in changes of erythrocyte membrane structure and function in hypertension. In order to characterize the structure of membrane proteins of erythrocytes from spontaneously hypertensive rats (SHR) the spin-label technique with a maleimide spin-label was used. A significant difference was observed in the characteristic electron-spin resonance (e.s.r.) spectrum of the label between samples from normotensive rats and SHR. The difference was eliminated and the spectrum significantly changed after treatment of the labelled membrane with EDTA followed by washing out the EDTA extracts, whereas the same treatment with EDTA without the following washing had no effect on the e.s.r. spectrum. It is concluded that the EDTA extracts different substances in the different rat groups. The spin-label technique is a useful method for distinguishing cell membrane properties in SHR and normotensive rats.

Animals↗
PubMed1986

[The Ca pump and Ca ATPase in the erythrocytes of patients with hypertension: disorders detected in cytoskeletal membranes and in solubilized Ca ATPase].

A study of Ca-ATPase and Ca-pump activity of the erythrocyte membrane's inverted vesicles with different cytoskeletal protein status demonstrated that Ca-pump activity remained unchanged, and Ca-ATPase activity was increased by 20-40%, as compared to erythrocytes from the normotensive controls, in hypertensive patients in the absence of exogenous calmodulin. These differences are assumed to be due to disorders of erythrocyte membrane structure in primary hypertension resulting in less efficient Ca-pump operation in the inverted vesicles. In all types of membranes obtained from hypertensive patients' erythrocytes in conditions of iso-osmotic hemolysis, calmodulin-induced increment of peak Ca-ATPase and Ca-pump activity was 2 or 3 times as low as that of normotensive controls. These differences remained in evidence after the solubilization of membrane proteins with triton X-100. No differences in calmodulin influence on Ca-ATPase affinity to Ca2+ could be found. The membranes obtained in iso-osmotic conditions demonstrated no calmodulin effect on Ca-ATPase activity which is attributed to partial proteolysis of the enzyme's molecule.

Adult↗
PubMed1986

[Mechanism of the change in erythrocyte osmotic resistance in rats exposed to valinomycin: the features seen in spontaneous hypertension].

Introduction of valinomycin into erythrocyte incubation medium increased the cell stability to water-induced hemolysis. In these conditions the erythrocytes of spontaneously hypertensive and normotensive (control) rats release 63.2 +/- 1.5% and 80.9 +/- 1.6%, respectively, of the total hemoglobin content. Valinomycin effect is completely abolished with K+ substitution for Na+ and is independent of extracellular Ca2+ concentration. Valinomycin had no effect on human erythrocyte osmotic stability. It has been shown that valinomycin-induced kinetics of Na+ and K+ redistribution was different in human and rat erythrocytes. The distinctions are thought to be related to specific anion transport mediated by the third band protein--the main component of membrane cytoskeleton.

Animals↗
PubMed1986

[Calcium transport in erythrocytes loaded with a highly selective Ca2+ chelator. The characteristics associated with primary hypertension].

The kinetics of 45Ca accumulation was studied in erythrocytes loaded with highly-selective Ca2+ chelator quin-2. Ca2+ erythrocyte penetration rate was increased by 20-30%, and free intracellular calcium (Ca2+ in), by 40-50%, in hypertensive patients, as compared to normotensive controls. Spontaneously hypertensive rats showed no differences in this respect. The addition of valinomycin and quinidine produced a tenfold increase in Ca2+ penetration rate in human erythrocytes and a 1.5-2-fold increase in rat erythrocytes. Under these conditions, the erythrocyte Ca2+ penetration rate and Ca2+ in concentration were increased by 40 and 60%, respectively, in spontaneously hypertensive rats. Hypertensive patients showed no differences. After incubation with the Ca-ATPase inhibitor orthovanadate, erythrocyte calcium level in the absence of quin-2 was 2-3 times as high in spontaneously hypertensive rats as it was in control animals.

Adult↗
PubMed1985

[Membrane potential and transport of neuromediators in synaptosomes of the brain of rats with spontaneous hypertension].

The transport of 3H-GABA, 14C-choline, 14C-noradrenaline and 3H-serotonin in brain synaptosomes of spontaneously-hypertensive rats (SHR) which is controlled by the carrier whose activity is dependent on the sodium gradient and electric potential of the plasma membrane was studied. The initial rate of GABA uptake by SHR synaptosomes was reduced by 25%. The steady state of the content of GABA, noradrenaline and serotonin in SHR synaptosomes was reduced by 15-20%, whereas the steady state of choline content by 35%. The differences are levelled when synaptosomes are depolarized, both due to the elimination of K+-diffusion potential, and the opening of Na channels. An increase in the extracellular calcium concentration up to 1 mmol results in a 20% synaptosomal GABA rise that is unrelated to membrane hyperpolarization. In the presence of the Ca-ionophore A-23187, a similar effect is observed with a 1-2 mmol Ca2+ concentration. The electric potential of SHR synaptosomes which is studied by means of the fluorescent dye dis-C3-(5) was shown to be reduced by 5-10 mV. Partial depolarization of SHR synaptosomes is supposed to be the principal cause of the decrease in both the initial rate of uptake and the steady state of the content of neuromediators.

Acetylcholine↗
PubMed1985

[Mechanism of the effect of EGTA on the affinity to calcium of Ca-transporting and Ca-binding cell systems].

The activity of Ca-ATPases of erythrocyte ghosts and sarcoplasmic reticulum and the rate of ATP-dependent uptake of 45Ca by erythrocyte membrane inside-out oriented vesicles, sarcoplasmic reticulum vesicles and mitochondria were investigated. It was found that in all cases studied the addition of EGTA to the incubation mixture caused an increase in the affinity of Ca-pumps for Ca2+; their maximal activity remained thereby unaffected. A similar effect of EGTA was observed when the affinity for Ca2+ of calmodulin, troponin C and the fluorescent dye quin 2 were determined. It was assumed that the effect of EGTA on the affinity for Ca2+ of Ca-transporting and Ca-binding systems of a cell is due to a removal of admixtures of bi- and trivalent cations.

Animals↗
PubMed1985

[Mechanism of increase in Ca2+ level in platelet cytoplasm induced by aggregating factors].

Using the fluorescent dye, quin-2, it was shown that addition of ADP, thrombin and the so-called platelet activation factor (PAF) to a human platelet suspension results in a 5-20 increase in the concentration of free Ca2+ (Ca2+in) in the cytoplasm. No ADP and PAF-stimulated increase in Ca2+in occurs, when the concentration of extracellular Ca2+ sharply diminishes prior to addition of these agents; the value of the thrombin-stimulated increase in Ca2+in decreases by one order of magnitude under these conditions. Verapamil (10(-4) M) completely blocks the effect of PAF on Ca2+in concentration and decreases 2-3 times the response to ADP; in the case of thrombin verapamil increases the time necessary for the full response without changing its maximum value. Depolarization of the platelet plasma membrane after removal of the K+ diffusion potential does not affect Ca2+ content in the cytoplasm. No significant effect of ADP, thrombin or PAF on the electric potential of the platelet membrane followed by the intensity of diS-C3-(5) fluorescence was found. The elevation of the cAMP content in platelets after addition of prostaglandin E1, forskolin or papaverine leads to a removal of the PAF and ADP effects on the Ca2+in level. The data obtained suggest that the increase in Ca2+ content in platelet cytoplasm caused by the above-mentioned aggregation factors is due to the opening of the receptor-sensitive channels.

Alprostadil↗
PubMed1985

[Isolation and characteristics of calmodulin from the brains of rats with spontaneous genetic hypertension].

Using column chromatography with phenylcepharase, calmodulin was isolated from the brain of rats with spontaneous hypertension (SHR) and control normotensive rats (NKWR). As judged from the findings of electrophoresis in polyacrylamide gel, UV-spectroscopy and spectrofluometry, the obtained samples of calmodulin contained no significant admixture of other proteins. The Ca-binding capacity of calmodulin of the brain of SHR and NKWR estimated by the method of fluorescent probes were identical. There were also no differences in their capacity to interact with troponine I and to activate the Ca-pump of the erythrocytic membrane and phosphodiesterase of the cardiac muscle. A study on the dependence of activity of phosphodiesterase on the protein content of the brain homogenate from SHR and NKWR revealed no differences in the calmodulin levels in this tissue. On the basis of these data a conclusion was made that impairments of the intracellular distribution of calcium in primary hypertension described earlier are not related to disorders in the metabolism of the universal Ca-binding protein-regulator.

Animals↗
PubMed1985

[The use of parameters of non-uniform widening of probe fluorescence spectra in the study of conformation changes in Ca2+-binding proteins].

The parameters of inhomogeneous broadening in the fluorescence spectra of 1-anilinonaphthalene-8-sulfonate and N-phenyl-1-naphthylamine, recorded in the systems with respective proteins, have been analyzed in order to shed light on the mechanism of interaction between Ca2+ ions and calmodulin, troponin C and parvalbumin. It was shown that only calmodulin and troponin C but not parvalbumin bind calcium ions with concomitant formation of hydrophobic sites that are responsible for interaction with the "executor enzymes". The relative pools of the probes adsorbed in the hydrophobic sites and polarity of the latter were assessed. These parameters in calmodulin obtained from the brain of spontaneously hypertensive rats or normotensive rats do not differ. It was established that trifluoroperazine and verapamil inhibit the calmodulin-dependent enzymes by essentially different mechanisms. Trifluoroperazine diminishes the relative pool of the adsorbed probe and enhances the polarity of the calmodulin binding sites, whereas verapamil affects these parameters in the opposite direction.

1-Naphthylamine↗
PubMed1985

[The role of free calmodulin in the regulation of calcium-pump activity in erythrocytes].

The activity of Ca-pump in inside-out oriented vesicles obtained from erythrocyte membranes after their 30 min treatment with EGTA at 20 degrees C (membranes A) and 37 degrees C (membranes B) was investigated. It was shown that in membranes A placed into an incubation medium containing 0.1 mM EGTA (pH 7.4) the overall effect of exogenous calmodulin is due to the increase in the maximal activity of the enzyme, its affinity for Ca2+ being unaffected thereby. In membranes B placed into the same medium (pH 6.75) the activation of the Ca-pump by calmodulin is due to the increased affinity for Ca2+ at a constant maximal activity of the enzyme. The dependencies of the value of the calmodulin-stimulated component of membranes A and the Ca2+-binding capacity of calmodulin measured by the intensity of N-phenyl-1-naphthylamine fluorescence on the concentration of free Ca2+ are coincident. In the case of membranes B, the stimulation of Ca-pump by calmodulin occurs at much lower Ca2+ concentrations than the Ca2+ binding-induced conformational shifts in calmodulin. The experimental results suggest that the affinity of the Ca-pump for Ca2+ may affect calmodulin existing in a Ca2+-independent state. The hydrophobic interactions between the Ca-calmodulin complex and the Ca-ATPase molecule are apparently essential for the regulation of the maximal enzyme activity.

Animals↗
PubMed1985

[Mechanism of involvement of calmodulin in the regulation of affinity to Ca2+ and maximum activity of Ca-pump in the erythrocyte membrane].

The activity of the Ca-pump in inside-out oriented human erythrocyte membrane vesicles was studied with the use of 45Ca and membrane filters. It was found that trifluoroperazine fully inhibits the calmodulin-induced increase in the maximal activity of the Ca-pump without affecting the calmodulin-stimulated increase in the Ca-pump affinity for Ca2+. The dependence of calcium concentrations of calmodulin-stimulated components of the Ca-pump activity, both inhibited and noninhibited by trifluoroperazine, as well as the dependence on calcium concentrations of the fluorescence intensity of N-phenyl-1-naphthylamine were analyzed. This analysis revealed essential differences between the mechanisms of calmodulin action on the maximal activity of the Ca-pump and its affinity for Ca2+. The maximal activity was elevated by addition of the Ca-calmodulin complex, whereas the increase in the affinity for Ca2+ was induced by calmodulin alone. These findings were supported by data on the dependence of the Ca-pump activity on calmodulin concentrations at low and saturating concentrations of Ca2+ as well as by data obtained in the study on moderate treatment of erythrocyte membranes with trypsin.

Biological Transport↗
PubMed1984

Aggregation, membrane potential, and transport in platelets of spontaneously hypertensive rats.

Aggregation, plasma membrane potential, and calcium uptake by platelets of spontaneously hypertensive rats (SHR) were studied. The sensitivity of SHR platelets to the action of ADP and collagen was increased. The addition of Ca-ionophore (A-23187) resulted in aggregation of SHR platelets at a Ca2+ concentration in the incubation medium 20%-30% lower than that required for aggregation of platelets from normotensive rats. The plasma membrane of SHR platelets was found to be partially depolarized (by 8-10 mV) as compared to that of normotensive controls. This difference was apparently due to a higher membrane permeability for Na+. It is suggested that the increase in 45Ca uptake by SHR platelets is related to an increased rate of Ca2+ diffusion along a potential-dependent channel, due to partial depolarization of plasma membrane.

Animals↗
PubMed1984

Calmodulin distribution and Ca2+ transport in the erythrocytes of patients with essential hypertension.

The rate of calcium transport and calmodulin distribution in the erythrocytes of patients with essential hypertension were studied. In erythrocyte membranes subjected to calmodulin depletion by treatment with EGTA, both the affinity of the calcium pump for Ca2+ and its maximal activity were the same in normotensive and hypertensive patients. The addition of exogenous calmodulin to calmodulin-stripped membranes from erythrocytes of patients with essential hypertension resulted in a smaller increase of the maximal activity of the calcium pump and its affinity for Ca2+. The addition of calmodulin to erythrocyte membranes obtained without EGTA treatment resulted in a smaller increase of the maximal activity of the calcium pump only. There were no significant differences of calmodulin distribution (cytoplasmic concentration and size of the membrane-bound pool) between the erythrocytes of normotensive and hypertensive patients. It is suggested that alterations in the calcium pump activity of the erythrocyte membranes of patients with essential hypertension are related to the alteration of interaction between calmodulin and Mg2+, Ca2+-ATPase.

Adult↗
PubMed1984

Microcalorimetry and electrophoresis of the erythrocyte membrane of spontaneously hypertensive rats.

Abnormalities of both structure and function have been described in the erythrocyte membrane of spontaneously hypertensive rats (SHR). In order to elucidate the molecular basis of these abnormalities we have carried out differential scanning microcalorimetry of the erythrocyte membrane and gel electrophoresis of membrane polypeptides. The partial enthalpy of so-called 'C-transition' (at 63 degrees C) was found to be increased. This may be explained by increased content of band 3 protein in SHR erythrocyte membrane.

Animals↗