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Journal ArticleDOI

In vivo and in vitro effects of aldrin on rat brain synaptosomal Mg2+ and Na+,K(+)-adenosine triphosphatase.

01 Oct 1990-Biochemical Pharmacology (Elsevier)-Vol. 40, Iss: 7, pp 1449-1456
TL;DR: It is suggested that aldrin increases the lipid fluidity of the synaptosomal membrane which may be a cause of inhibition of neuronal membrane-bound Na+,K+ and Mg2(+)-ATPase activities.
Abstract: Aldrin, a chlorinated hydrocarbon, inhibited rat brain synaptosomal membrane-bound Na + ,K + -adenosine triphosphatase (ATPase) and Mg 2+ -ATPase activities under in vivo and in vitro conditions. Na + ,K + -ATPase was non-competitively inhibited whereas Mg 2+ -ATPase was inhibited uncompetitively. Arrhenius plots of both these ATPases without aldrin under in vivo and in vitro conditions were found to be linear. In the presence of aldrin, on the other hand, Arrhenius plots of the same ATPases were nonlinear. Slopes of Arrhenius plots of both ATPases under in vivo and in vitro condition were changed with change in temperature with aldrin. The activation energy (AE) of Na + ,K + -ATPase and Mg 2+ -ATPase activities were changed over the temperature range 15–40° in the presence of aldrin. These results thus suggest that aldrin increases the lipid fluidity of the synaptosomal membrane which may be a cause of inhibition of neuronal membrane-bound Na + ,K + and Mg 2+ -ATPase activities.
Citations
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Journal ArticleDOI
TL;DR: Diverse compounds that have been claimed to be inhibitors of ATP‐metabolising ectoenzymes are evaluated, but specific and selective Ca2+ /Mg2+ ‐dependent ecto‐ATPase inhibitors still appear to be lacking.
Abstract: Extracellular ATP can produce various effects acting via P2-purinoceptors. ATP is rapidly broken down by ecto-ATPase and other ecto-enzymes that limit its effect. Further, adenosine, a metabolite of ATP breakdown, can produce its own effect acting via P1-purinoceptors, sometimes masking the effects of ATP. An inhibitor of ATP degradation would be a useful pharmacological tool to discriminate between effects of ATP and its metabolites, as well as to potentiate its actions. Diverse compounds that have been claimed to be inhibitors of ATP-metabolising ectoenzymes are evaluated, but specific and selective Ca2+ /Mg2+ -dependent ecto-ATPase inhibitors still appear to be lacking.

123 citations

Journal ArticleDOI
TL;DR: The potent interaction of selected pesticides and chemicals with the vesicular transporter for dopamine, although, by itself, not synonymous with neurotoxicity, would argue for a likely impairment of transmitter homeostasis, or the putative formation of neurodegenerative toxin pools.
Abstract: This study defined the ability of a large sample of heterogeneous pesticides and neurotoxins to interact with the [3H]tyramine-labelled vesicular transporter of dopamine in rat striatum. Botanical (with rotenone as the most potent), and organochlorine (Kepone) insecticides, as well as fungicides (Zineb), as a whole, consistently inhibited [3H]tyramine binding, with Ki values ranging from 5 nM to 10 μM. ATP/Mg2+-dependent [3H]tyramine uptake to purified striatal synaptic vesicles was also inhibited by rotenone. Organophosphate and carbamate insecticides, and miscellaneous herbicides poorly antagonized [3H]tyramine binding, yielding Ki values exceeding 10 μM. Several, though not all, of the best recognized central neurotoxins tested were major binding antagonists. Their rank order of potency was 1-methyl-4-phenylpyridinium ion (MPP+) > trimethyltin ≥ 6-hydroxydopamine > N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) > 1-methyl-4-pheny;-1,2,3,6-tetrahydropyridine (MPTP), with Ki values ranging from 35 nM to 3 μM. Overall, the potent interaction of selected pesticides and chemicals with the vesicular transporter for dopamine, although, by itself, not synonymous with neurotoxicity, would argue for a likely impairment of transmitter homeostasis, or the putative formation of neurodegenerative toxin pools.

23 citations

References
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Journal Article
TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
Abstract: Since 1922 when Wu proposed the use of the Folin phenol reagent for the measurement of proteins, a number of modified analytical procedures utilizing this reagent have been reported for the determination of proteins in serum, in antigen-antibody precipitates, and in insulin. Although the reagent would seem to be recommended by its great sensitivity and the simplicity of procedure possible with its use, it has not found great favor for general biochemical purposes. In the belief that this reagent, nevertheless, has considerable merit for certain application, but that its peculiarities and limitations need to be understood for its fullest exploitation, it has been studied with regard to effects of variations in pH, time of reaction, and concentration of reactants, permissible levels of reagents commonly used in handling proteins, and interfering substances. Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.

289,852 citations

Journal ArticleDOI
TL;DR: On the basis of the assumed theory the rate of the observed reaction is directly proportional to the concentration of the enzyme-substrate compound, where (E:l = (ES).
Abstract: On the basis of the assumed theory the rate of the observed reaction is directly proportional to the concentration of the enzyme-substrate compound, (ES), a t all values of the concentration of the substrate, (S). It is proportional to (S) only a t low values of (S). The numerical value of the dissociation constant is given by the substrate concentration a t half-maximum velocity, where (E:l = (ES). The equilibrium in equation 1 may be heterogeneous or homogeneous. Hitchcock'\" has pointed

11,349 citations

Journal ArticleDOI
TL;DR: Afhnity for Monovalent Cations and Quantitative Relation between Effect of Na+ + K+ on Enzyme System and Active Transport in Intact Cell.
Abstract: Afhnity for Monovalent Cations. 597 Relationship of Enzyme System to ATP. 598 Isolation of Enzyme System from Other Cells with Active Transport of Na+ and K+ 602 Location of Enzyme System in the Cell. 604 Effect of Cardiac Glycosides. 605 Quantitative Relation between Effect of Na+ + K+ on Enzyme System and Active Transport in Intact Cell. 606 Nature of Enzyme System. 607 Relation of (Na + + K+)-Activated Enzyme System to Active Transport of Cations. 6 10 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6’4

1,946 citations

Journal ArticleDOI
Jens Chr. Skou1
TL;DR: Leg nerves from the shore crab contain an adenosine triphosphatase which is located in the submicroscopic particles, and the influence of sodium, potassium, magnesium and calcium ions on this enzyme has been investigated.
Abstract: Leg nerves from the shore crab (Carcinus maenas) contain an adenosine triphosphatase which is located in the submicroscopic particles. The influence of sodium, potassium, magnesium and calcium ions on this enzyme has been investigated. The presence of magnesium ions is an obligatory requirement for the activity of the enzyme. Sodium ions increase the activity when magnesium ions are present. Potassium ions increase the activity when the system contains both magnesium and sodium ions. Potassium ions in high concentration inhibit that part of the activity which is due to Na+, while the activity due to Mg++ is not affected. Calcium ions inhibit the enzyme under all conditions. When Mg++ or Mg++ + Na+ are present in the system, the optimum magnesium concentration is equal to the concentration of ATP. If potassium ions are added, the optimum magnesium concentration is doubled. If calcium ions are also added, the optimum magnesium concentration becomes still higher, and it increases with the calcium concentration. A majority of these observations may be explained by assuming (a) that the substrate most readily attacked by the enzyme is sodium-magnesium-ATP, (b) that potassium ions stimulate the enzyme directly, and (c) that an increase in the concentration of potassium ions leads to a displacement of sodium ions from the substrate and accordingly to an inhibition of the reaction. If the system contains the four cations in concentrations roughly equal to those in the crab-nerve axoplasm, an increase in the sodium concentration as well as a decrease in the potassium concentration will lead to an intensification of the enzyme activity. This observation, as well as some other characteristics of the system, suggest that the adenosine triphosphatase studied here may be involved in the active extrusion of sodium from the nerve fibre.

1,800 citations