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D Lichtstein

Publications and source records attributed to D Lichtstein.

53 records · Page 3Linked to original sources
PubMed1986

Characterization of two classes of cardiac glycosine binding sites in rat heart and brain membrane preparations, using quantitative computer modelling.

Cardiac glycoside binding to rat heart and brain membrane preparations was measured by a rapid filtration technique. Data were analysed using quantitative computer analysis. The experimental results were consistent with a model in which cardiac glycoside-specific binding occurs at two independent classes of sites. The high-affinity sites in heart membranes were characterized by dissociation constants (Kd) of 40, 50, and 61 nmol/l for ouabain, digoxin and digitoxin, respectively, and the lower-affinity sites were characterized by Kd of 2.3 mumol/l, 67 nmol/l and 71 nmol/l for ouabain, digoxin and digitoxin, respectively. Comparable results were obtained using brain membranes. Potassium ions inhibit [3H]-ouabain binding in a dose-dependent manner with an IC50 of 500 mumol/l. Quantitative computer modeling indicated that potassium inhibits ouabain binding to approximately the same extent at both classed of binding sites, consistent with the hypothesis that the two classes of binding sites for cardiac glycosides might be associated with the Na+K+-ATPase.

Animals↗
PubMed1985

Basic characterization of an ouabain-resistant, bumetanide-sensitive K+ carrier-mediated transport system in J774.2 mouse macrophage-like cell line and in variants deficient in adenylate cyclase and cAMP-dependent protein kinase activities.

86Rb(K+) transport across the plasma membrane of macrophage-like cells was studied. The cells used were the wild-type J774.2 and its two variants, CT2 cells, deficient in adenylate cyclase, and J7H1 cells, deficient in cAMP-dependent protein kinase. In the three cell lines about 15% of the total 86Rb(K+) influx is transported by the K+ carrier-mediated transport system. The 86Rb(K+) efflux carried by the same transporter is negligible when measured in the absence of ouabain in the medium. Therefore this carrier conducts a net inward flux of K+ under the experimental conditions used. The transporter is sensitive to extracellular Na+ and inhibited by 'loop' diuretics; bumetanide inhibits ouabain-resistant 86Rb(K+) influx with IC50 of 0.1, 5.0, and 0.05 microM for J774.2, CT2 and J7H1 macrophages, respectively. The membrane potential of the three cells was measured, using the distribution of [3H]tetraphenylphosphonium [( 3H]TPP+) across the plasma membrane, and found to be -80.1, -108.5 and -105.1 mV for J774.2, CT2 and J7H1 cells, respectively. The addition of bumetanide to the cell medium does not alter [3H]TPP+ uptake indicating that the transporter is electrically silent. It is concluded that despite the differences in cAMP metabolism by the three macrophages, the basic characteristics of K+ carrier-mediated transport system of the three cells are very similar.

Adenylyl Cyclases↗
PubMed1985

Evidence for the presence of 'ouabain like' compound in human cerebrospinal fluid.

Material extracted and partially purified from human cerebrospinal fluid (CSF) is capable of: a, inhibiting [3H]ouabain binding to rat brain synaptosomes; b, inhibiting the activity of purified pig kidney Na+,K+-ATPase; and c, inhibiting ouabain sensitive induced 86Rb influx to tissue cultured fibroblasts. These results demonstrate the existence of an 'ouabain like' compound (OLC) in human CSF, and are consistent with the hypothesis of the function of this compound as a neuromodulator.

Binding Sites↗
PubMed1984

Comparison between bretylium and diphenylhydantoin interaction with mucosal sodium-channels.

The antifibrillatory drug bretylium and the antiepileptic drug diphenylhydantoin cause an increase in the potential different and in the short-circuit current (SCC) across frog skin when added to the outer surface. The effect of both drugs depends upon the presence of sodium ions in the outer medium and is blocked by the specific sodium channel blocker, amiloride. Quantitative analysis shows that amiloride binds to open as well as closed mucosal sodium channel with the same affinity. The effects of diphenylhydantoin and bretylium differ with respect to their dependence on external pH. The diphenylhydantoin or the bretylium stimulatory effects are additive to the effects of oxytocin. In most cases the diphenylhydantoin and bretylium effects are also additive. It is concluded that the external side of the mucosal Na+ channels contains sites which interact specifically with either bretylium or diphenylhydantoin and thus remove the sodium induced closure of the channels.

Amiloride↗
PubMed1982

Bretylium opens mucosal amiloride-sensitive sodium channels.

Addition of the quanternary ammonium compound, bretylium, to the outer surface of a frog skin leads to an increase in the potential difference and in the short circuit current across the skin. Bretylium does not have any effect when applied to the inside face of the frog skin. The effect of bretylium is dependent upon the presence of sodium ions in the outer medium; it is depressed when sodium is replaced by choline or potassium but not when lithium substitutes for sodium. The bretylium effect is blocked by the specific sodium channel blocker, amiloride. It is proposed that bretylium opens mucosal, amiloride-sensitive sodium channels.

Amiloride↗
PubMed1982

Hyperpolarization of neuroblastoma-glioma hybrid NG108-15 by vanadium ions.

Vanadate hyperpolarizes mouse neuroblastoma-glioma hybrid NG108-15 by 20-30 mV. These changes in membrane potential (delta psi) are observed by monitoring the equilibrium distribution (intracellular/extracellular) of the lipophilic cation [3H]tetraphenylphosphonium (TTP+) and by directly measuring delta psi with intracellular microelectrodes. In physiological media (i.e., 135 mM NaCl/5 mM KCl), the half-maximal effective concentrations of sodium orthovanadate (Na3VO4) and sodium metavanadate (NaVO3) are 35 and 160 microM, respectively. The maximal effects for both these ions are quantitatively indistinguishable. The hyperpolarizing responses to vanadate occur without any observable lag, have t1/2 less than or equal to 30 sec, and are always accompanied by simultaneous decreases in membrane resistance. Neither ouabain nor media containing high K (i.e., 120 mM) devoid of Na and K (isotonicity maintained by choline) prevent the change in delta psi induced by vanadate. Therefore, vanadate produces a unique hyperpolarization which does not depend upon Na, K, or the Na/K pump. Furthermore, the accompanying decreases in membrane resistance indicate that vanadate must increase the permeability of the membrane to some ion. Our data are consistent with it being an anion, such as chloride or vanadate itself. Finally, vanadate hyperpolarizes many different types of cultured cells, only some of which are of neuronal origin. This indicates that a hyperpolarization of delta psi must be considered in any assessment of the physiological actions of the vanadates.

Animals↗
PubMed1982

Membrane potential changes induced by the ouabain-like compound extracted from mammalian brain.

The electrical membrane potential (delta psi) of chicken embryo fibroblasts in tissue culture was determined to be -30.5 +/- 2.9 mV as measured by distribution of the lipophilic [3H]tetraphenylphosphonium cation (Ph4P+). Stimulation of the electrogenic activity of the Na+,K+-ATPase by the ionophore monensin induces a hyperpolarization of approximately 47 mV and a new delta psi of -77.3 +/- 5.7 mV. The effects of the cardiac glycoside ouabain and an "ouabain-like compound" (OLC), which was extracted and partially purified from sheep brain, were contrasted using both the resting and hyperpolarized fibroblasts. Addition of OLC or ouabain to the incubation medium for short periods of time does not alter the cells' resting delta psi. However, OLC and ouabain block monensin-induced hyperpolarization. The inhibitory effects of OLC, like ouabain, are dose dependent, with half-maximal inhibition occurring at an amount of OLC equivalent to that found in 1.6 g of brain (wet weight) per ml and at 0.85 microM ouabain. In addition, the maximal actions of ouabain and OLC are not additive. These results show that the endogenous OLC specifically affects the delta psi of intact cells by a mechanism analogous to that of ouabain--i.e., inhibition of the Na+,K+-ATPase.

Animals↗
PubMed1982

Characterization of ouabain receptor in neuronal tissue: evidence for endogenous ouabain-like compound.

This study shows that [3H]ouabain binds specifically to a single, saturable binding site located on rat brain membranes with an affinity constant of 6.21 X 10(-8) M. As expected from studies on the mechanics of the Na+,K+-ATPase, sodium increased while potassium and lithium decreased ouabain binding. The occupation of other neurotransmitter receptors did not affect [3H]ouabain binding. Based on its ability to compete with [3H]ouabain binding and to inhibit Na+,K+-ATPase, it is suggested that rat brain extract contains an endogenous ouabain-like compound. The results are discussed with respect to the possibility that the ouabain receptor is a physiological regulatory site of the Na+,K+-ATPase activity.

Adenosine Triphosphatases↗
PubMed1981

Membrane potential of olfactory bulb synaptosomal fractions: characterization with the lipophilic cation tetraphenylphosphonium.

The membrane potential of olfactory bulb synaptosomal fractions was monitored with the lipophilic cation tetraphenylphosphonium (TPP+), which has been reported to distribute across membranes according to the Nernst equation. The properties of the synaptosomal membrane potential as monitored with TPP+ were similar to those reported for neural tissues using other measurement techniques. There is an electrical potential (delta psi) of -64 and -77 mV in the P1 and P2 synaptosomal fractions, respectively. This potential is due primarily to the K+ diffusion gradient across the synaptosomal membrane. The influence of ouabain on TPP+ accumulation indicates that the (Na+,K+)-ATPase electrogenicity contributes about -20 mV to the resting synaptosomal membrane potential. Veratridine induced a decline in TPP+ accumulation which was blocked by tetrodotoxin or by the omission of Na+ from the medium. A significant mitochondrial contribution to TPP+ accumulation, which varied as a complex function of TPP+ concentration in the medium in a manner indicating that TPP+ interfered with the maintenance of mitochondrial potential, was observed. This mitochondrial contribution could be eliminated by performing the experiments anaerobically in the presence of oligomycin. The results are discussed with relation to the future possible use of TPP+ for delta psi measurements in synaptosomal preparations.

Animals↗
PubMedDate not supplied

Endogenous ouabain-like compound increases heart muscle contractility.

Cardiac glycosides such as digoxin or ouabain have long been known to influence the strength of contraction of cardiac muscle. Although the mechanism of action of these compounds remains unknown, all the proposed modes of action are based on initial binding to specific membrane receptors which are part of the (Na+ + K+)ATPase complex. These receptors, well characterized and defined, suggest the existence of an endogenous substance capable of binding to them, in analogy with endogenous opiates, discovered long after morphine and its receptors. As glycosides affect (Na+ + K+)ATPase activity, an endogenous substance may be a regulator of this important enzyme. Indeed, the search for endogenous regulators of the (Na+ + K+)ATPase or ouabain-like compounds (OLC) has recently intensified. These compounds, extracted and partially purified from mammalian brain, heart, blood and urine, and from toad skin and plasma, have been shown to inhibit 3H-ouabain binding and (Na+ + K+)ATPase activity. We report here that in addition to these effects, the OLC, highly purified from toad skin and sheep brain, increases the force of contraction of frog and guinea pig atrium.

Animals↗
PubMedDate not supplied

Demonstration of a ouabainlike plasma compound in hypertension prone and hypertension resistant rats.

Material extracted and partially purified from plasma of the Sabra hypertension prone rats was found to be capable of 1) inhibiting the binding of 3H-ouabain to rat brain synaptosomes, 2) inhibiting the activity of rat brain microsomal Na, K activated adenosine triphosphatase, and 3) increasing the contractile force of rat heart muscle. The results demonstrate the presence of a ouabainlike compound in the plasma of these rats. The plasma concentration of this compound in Sabra hypertension prone rats was 698 +/- 199 nmol/ml in ouabain equivalents (SEM; n = 11) versus 2543 +/- 1140 nmol/ml (n = 9) in the Sabra normotensive strain. The presence of ouabainlike compound in the plasma is consistent with the hypothesis that this compound functions as a hormone that regulates Na, K activated adenosine triphosphatase activity and the physiological processes in which this enzyme is involved.

Animals↗
PubMedDate not supplied

Digitalis-like compounds in animal tissues.

The Na+, K+ activated adenosine triphosphatase is present in the membrane of eukaryotic cells and represents a major pathway for Na+ and K+ transport across the plasma membrane. Cardiac glycosides such as ouabain or digoxin suppress this enzyme activity by binding to a specific receptor on the membrane. Studies conducted in this and other laboratories have proven the existence of digitalis-like compounds in animal tissues which may serve as in vivo regulators of the Na+, K(+)-pump activity. This review summarizes the attempts to identify these compounds from animal tissues and examines the potential physiological role of some of the identified compounds.

Animals↗
PubMedDate not supplied

Distribution of atrial natriuretic peptides in the sand rat (Psammomys obesus) in comparison to that in the rat.

Atrial natriuretic peptides (ANP) are a family of humoral compounds involved in water and salt homeostasis. Immunoreactive ANP (IR-ANP) was determined in the plasma and tissues of the rat and the sand rat (Psammomys obesus) using sensitive and specific radioimmunoassay. IR-ANP from the rat and the sand rat elute at identical retention times from reverse phase HPLC indicating that the same chemical entity is present in both species. IR-ANP highest levels were found, in both species, in the heart but it was also present in the adrenal gland, lung, kidney, liver, plasma and several loci in the central nervous system. The IR-ANP levels in the heart, adrenal gland, kidney, liver, cerebellum and cerebral cortex were lower in the sand rat compared to the rat. The plasma IR-ANP level of the diabetes-resistant sand rat was further decreased to about 10% of the level in the diabetes-resistant sand rat.

Animals↗
PubMedDate not supplied

Bufodienolides as endogenous Na+, K+-ATPase inhibitors: biosynthesis in bovine and rat adrenals.

The biosynthesis of digitalis-like compounds (DLC) was determined in bovine and rat adrenal homogenates by following changes in the concentration of DLC using three independent sensitive bioassays: inhibition of [3H]-ouabain binding to red blood cells and competitive ouabain and bufalin ELISA. The amounts of DLC in bovine and rat adrenal homogenates, as measured by the two first bioassays, increased with time when the mixtures were incubated under tissue culture conditions. These results suggest that Na+, K+-ATPase inhibitors which interact with ouabain antibodies, but not those which interact with bufalin antibodies, are synthesized in bovine and rat adrenals.

Adrenal Cortex↗
PubMedDate not supplied

Presynaptic modulation by endogenous ouabain-like substances of noradrenaline release from blood vessels.

The effect of an endogenous ouabain-like compound (OCL) and of ouabain was studied on [3H]noradrenaline release and on the tension of rabbit pulmonary arterial strip. Similarly to ouabain, the OLC enhanced release of [3H] NA in resting and in stimulated condition. Moreover, in the presence of OLC and ouabain, the tension of the rabbit artery increased gradually and the contraction evoked by electrical stimulation was potentiated. It is suggested that this mechanism might be involved in the physiological regulation of blood pressure or in the genesis of hypertension.

Animals↗