skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Membrane events and ionic processes involved in dopamine release from tuberoinfundibular neurons. I. Effect of the inhibition of the Na+,K+-adenosine triphosphatase pump by ouabain

Abstract

In the present study we investigated the membrane events and the ionic processes which mediate the stimulatory effect of ouabain on the release of endogenous dopamine (DA) and previously taken-up (3H)DA release from rat hypothalamic tuberoinfundibular dopaminergic (TIDA) neurons. Ouabain (0.1-1 mM) dose-dependently stimulated endogenous DA and newly taken-up (3H)DA release. This effect was counteracted partially by nomifensine (10 microM). Removal of Ca++ ions from the extracellular space in the presence of the Ca++-chelator ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid prevented completely ouabain-elicited (3H)DA release. Lanthanum (1 mM) and cobalt (2 mM), two inorganic Ca++-entry blockers, were able to inhibit this stimulatory effect, whereas verapamil (10 microM) and nitrendipine (50 microM), two organic antagonists of the voltage-operated channel for Ca++ ions, failed to affect ouabain-induced (3H)DA release. By contrast, adriamycin (100-300 microM), a putative inhibitor of cardiac Na+-Ca++ antiporter, dose-dependently prevented ouabain-induced (3H)DA release from TIDA neurons. Finally, tetrodotoxin reduced digitalis-stimulated (3H)DA release. In conclusion, these results seem to be compatible with the idea that the inhibition of Na+,K+-adenosine triphosphatase by ouabain stimulates the release of (3H)DA from a central neuronal system like the TIDA tract and that this effect is critically dependent on the entrance of Ca++ ions into themore » nerve terminals of these neurons. In addition the Na+-Ca++ exchange antiporter appears to be the membrane system which transports Ca++ ions into the neuronal cytoplasm during Na+,K+-adenosine triphosphatase inhibition. The enhanced intracellular Ca++ availability triggers DA release which could occur partially through a carrier-dependent process.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Univ. of Naples (Italy)
OSTI Identifier:
6805347
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Pharmacol. Exp. Ther.; (United States); Journal Volume: 246:2
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; CALCIUM COMPOUNDS; MEMBRANE TRANSPORT; DOPAMINE; SECRETION; OUABAIN; BIOLOGICAL EFFECTS; ATP-ASE; CATIONS; CELL MEMBRANES; COBALT; DOSE-RESPONSE RELATIONSHIPS; DOXORUBICIN; HYPOTHALAMUS; IN VITRO; INHIBITION; LANTHANUM; NERVE CELLS; PORINS; RATS; RESPONSE MODIFYING FACTORS; TRACER TECHNIQUES; TRITIUM COMPOUNDS; ACID ANHYDRASES; ALKALINE EARTH METAL COMPOUNDS; AMINES; ANIMAL CELLS; ANIMALS; ANTI-INFECTIVE AGENTS; ANTIBIOTICS; ANTINEOPLASTIC DRUGS; AROMATICS; AUTONOMIC NERVOUS SYSTEM AGENTS; BODY; BRAIN; CARBOHYDRATES; CARDIAC GLYCOSIDES; CARDIOTONICS; CARDIOVASCULAR AGENTS; CELL CONSTITUENTS; CENTRAL NERVOUS SYSTEM; CHARGED PARTICLES; DRUGS; ELEMENTS; ENZYMES; GLYCOSIDES; HYDROLASES; HYDROXY COMPOUNDS; IONS; ISOTOPE APPLICATIONS; LABELLED COMPOUNDS; MAMMALS; MEMBRANE PROTEINS; MEMBRANES; METALS; NERVOUS SYSTEM; NEUROREGULATORS; ORGANIC COMPOUNDS; ORGANS; PHENOLS; PHOSPHOHYDROLASES; POLYPHENOLS; PROTEINS; RARE EARTHS; RODENTS; SOMATIC CELLS; STROPHANTHINS; SYMPATHOMIMETICS; TRANSITION ELEMENTS; VERTEBRATES 550201* -- Biochemistry-- Tracer Techniques

Citation Formats

Taglialatela, M., Amoroso, S., Kaparos, G., Maurano, F., Di Renzo, G.F., and Annunziato, L. Membrane events and ionic processes involved in dopamine release from tuberoinfundibular neurons. I. Effect of the inhibition of the Na+,K+-adenosine triphosphatase pump by ouabain. United States: N. p., 1988. Web.
Taglialatela, M., Amoroso, S., Kaparos, G., Maurano, F., Di Renzo, G.F., & Annunziato, L. Membrane events and ionic processes involved in dopamine release from tuberoinfundibular neurons. I. Effect of the inhibition of the Na+,K+-adenosine triphosphatase pump by ouabain. United States.
Taglialatela, M., Amoroso, S., Kaparos, G., Maurano, F., Di Renzo, G.F., and Annunziato, L. 1988. "Membrane events and ionic processes involved in dopamine release from tuberoinfundibular neurons. I. Effect of the inhibition of the Na+,K+-adenosine triphosphatase pump by ouabain". United States. doi:.
@article{osti_6805347,
title = {Membrane events and ionic processes involved in dopamine release from tuberoinfundibular neurons. I. Effect of the inhibition of the Na+,K+-adenosine triphosphatase pump by ouabain},
author = {Taglialatela, M. and Amoroso, S. and Kaparos, G. and Maurano, F. and Di Renzo, G.F. and Annunziato, L.},
abstractNote = {In the present study we investigated the membrane events and the ionic processes which mediate the stimulatory effect of ouabain on the release of endogenous dopamine (DA) and previously taken-up (3H)DA release from rat hypothalamic tuberoinfundibular dopaminergic (TIDA) neurons. Ouabain (0.1-1 mM) dose-dependently stimulated endogenous DA and newly taken-up (3H)DA release. This effect was counteracted partially by nomifensine (10 microM). Removal of Ca++ ions from the extracellular space in the presence of the Ca++-chelator ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid prevented completely ouabain-elicited (3H)DA release. Lanthanum (1 mM) and cobalt (2 mM), two inorganic Ca++-entry blockers, were able to inhibit this stimulatory effect, whereas verapamil (10 microM) and nitrendipine (50 microM), two organic antagonists of the voltage-operated channel for Ca++ ions, failed to affect ouabain-induced (3H)DA release. By contrast, adriamycin (100-300 microM), a putative inhibitor of cardiac Na+-Ca++ antiporter, dose-dependently prevented ouabain-induced (3H)DA release from TIDA neurons. Finally, tetrodotoxin reduced digitalis-stimulated (3H)DA release. In conclusion, these results seem to be compatible with the idea that the inhibition of Na+,K+-adenosine triphosphatase by ouabain stimulates the release of (3H)DA from a central neuronal system like the TIDA tract and that this effect is critically dependent on the entrance of Ca++ ions into the nerve terminals of these neurons. In addition the Na+-Ca++ exchange antiporter appears to be the membrane system which transports Ca++ ions into the neuronal cytoplasm during Na+,K+-adenosine triphosphatase inhibition. The enhanced intracellular Ca++ availability triggers DA release which could occur partially through a carrier-dependent process.},
doi = {},
journal = {J. Pharmacol. Exp. Ther.; (United States)},
number = ,
volume = 246:2,
place = {United States},
year = 1988,
month = 8
}
  • In the present study we investigated the effect of amiloride, a rather specific inhibitor of the membrane Na+-Ca++ exchange system, on the release of endogenous dopamine (DA) and previously taken-up (3H)DA from tuberoinfundibular dopaminergic neurons. Amiloride (300 microM) stimulated either endogenous DA or (3H)DA release. Amiloride-induced stimulation of (3H)DA release was prevented in a Ca++-free plus ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid medium. Amiloride, at the same concentration, reinforced both high K+- and electrically-induced stimulation of (3H)DA release. These results are explained on the basis of the ability of amiloride in blocking the Na+-Ca++ exchange system, therefore causing an elevation ofmore » intracellular Ca++ levels in resting conditions, and a further accumulation of Ca++ ions after high K+- or electrically elicited opening of voltage-operated channels specific for Ca++ ions. The enhanced intracellular Ca++ availability may trigger the stimulation of neurotransmitter release. In addition, amiloride was able to block in a dose-dependent manner (70-300 microM) the ouabain-induced (3H)DA release, suggesting that, when intracellular concentrations of Na+ are increased by the blockade of Na+,K+-adenosine triphosphatase the Na+-Ca+;+ exchange carrier reverses its resting mode of operation, mediating the influx of extracellular Ca++ ions. Amiloride, by blocking the Na+-Ca++ exchange mechanism, prevents the ouabain-elicited entrance of extracellular Ca++ ions, therefore inhibiting (3H)DA release stimulated by the cardioactive glycoside. Collectively, the results of the present study seem to be compatible with the idea that the Na+-Ca++ exchange mechanism is involved in the regulation of (3H)DA release from tuberoinfundibular dopaminergic neurons, through the regulation of Ca++ movements across the plasma membrane.« less
  • Mechanisms related to the inhibition of (H+ + K+)-adenosine triphosphatase (ATPase) by 2-(((3-methyl-4-(2,2,2-trifluoroethoxy)-2-pyridyl)methyl) sulfinyl)-1H-benzimidazole (AG-1749) were studied using canine gastric microsomes. AG-1749 (1-100 microM) inhibited the K+-stimulated ATP hydrolysis and vesicular accumulation of H+. AG-1749 bound to the microsomes concentration-dependently and decreased the number of free SH groups; the binding correlating with the enzyme inhibition. Both the binding and inhibition were antagonized by dithiothreitol. N-ethylmaleimide inhibited the (H+ + K+)-ATPase and decreased the binding of (/sup 14/C)AG-1749 to the microsomes. The inhibitory effect of AG-1749 gradually increased with incubation time, and was enhanced by lowering the pH. AG-2000 and AG-1812,more » acid-induced rearrangement products of AG-1749, inhibited (H+ + K+)-ATPase potently, rapidly and independently of pH; the inhibition was antagonized by dithiothreitol. We propose that AG-1749 is transformed into its active forms within the acidic compartment of the parietal cells and that the active compounds inhibit (H+ + K+)-ATPase activity by reacting with the SH groups of the enzyme.« less
  • Prolonged exposure to estradiol 17-..beta.. (E/sub 2/) in rats has been shown to decrease dopamine (DA) synthesis in and release from tuberoinfundibular dopaminergic (TIDA) neurons in Fischer 344 rats. The objective of the present study was to determine whether inhibition of the E/sub 2/-induced increase in anterior pituitary (AP) weight and prolactin (PRL) secretion by concomitant administration of the dopaminergic agonist, bromocryptine, could prevent the decrease in TIDA neuronal function produced by chronic E/sub 2/ administration. TIDA neuronal function was evaluated by in vitro superfusion and electrical stimulation of median eminence (ME) tissue after allowing for accumulation of (/sup 3/H)more » dopamine (DA). The effect of chronic E/sub 2/ and/or bromocryptine treatment on catecholamine content in tuberohypophyseal neurons in the neurointermediate lobe was also measured to determine whether increased pituitary size possibly damaged the tuberohypophyseal neurons.« less
  • The response of sodium, potassium-adenosine triphosphatase (Na,K-ATPase) to cyclic adenosine monophosphate (cAMP)-dependent protein kinase was examined in membranes obtained from rabbit iris-ciliary body. In the presence of the protein kinase together with 10(-5) M cAMP, Na,K-ATPase activity was reduced. No change in Na,K-ATPase activity was detected in response to the protein kinase without added cAMP. Likewise cAMP alone did not alter Na,K-ATPase activity. Reduction of Na,K-ATPase activity was also observed in the presence of the cAMP-dependent protein kinase catalytic subunit. The response of the enzyme to the kinase catalytic subunit was also examined in membranes obtained from rabbit ciliary processes.more » In the presence of 8 micrograms/ml of the catalytic subunit, ciliary process Na,K-ATPase activity was reduced by more than 50%. To examine whether other ATPases were suppressed by the protein kinase, calcium-stimulated ATPase activity was examined; its activity was stimulated by the catalytic subunit. To test whether the response of the ciliary process Na,K-ATPase is unique, experiments were also performed using membrane preparations from rabbit lens epithelium or rabbit kidney; the catalytic subunit significantly reduced the activity of Na,K-ATPase from the kidney but not the lens. These Na,K-ATPase studies suggest that in the iris-ciliary body, cAMP may alter sodium pump activity. In parallel 86Rb uptake studies, we observed that ouabain-inhibitable potassium uptake by intact pieces of iris-ciliary body was reduced by exogenous dibutryl cAMP or by forskolin.« less
  • Inhibition of renal Na+,K+-adenosine triphosphatase is an early biochemical manifestation of gentamicin treatment in rats. Studies with isolated, perfused rat kidneys in filtering and nonfiltering modes indicate that gentamicin is transported across the brush border membrane before enzyme inhibition. The drug caused enzyme inhibition (42%) only in filtering kidneys, and this inhibition was blocked by spermine, an inhibitor of gentamicin binding. In purified rat renal basolateral membranes, bound (/sup 3/H)gentamicin was displaced 88% by unlabeled gentamicin. After in vivo exposure to (/sup 3/H)gentamicin, the radioactivity associated with the isolated basolateral membranes was displaced only 46% by unlabeled drug. These resultsmore » suggest that inhibition of renal Na+,K+-adenosine triphosphatase by gentamicin is probably due to an interaction at the cytoplasmic face of the basolateral membrane. Scatchard plots of (/sup 3/H)gentamicin binding to basolateral and brush border membranes revealed a single class of noninteracting sites in each membrane. Gentamicin did not change the bulk membrane lipid fluidity, as estimated by the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene.« less