The effects of inorganic mercury in vitro on the release of ( sup 3 H)dopamine from rat striatal synaptosomes: Mechanisms of action

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5657388

Hare, M F

Inorganic mercury (Hg{sup 2+}) increases spontaneous neurotransmitter release from peripheral and central nervous system presynaptic nerve terminals. In rat striatal synaptosomes Hg{sup 2+} ({ge}2 {mu}M) increased spontaneous ({sup 3}H)dopamine release in a concentration-dependent fashion. These effects were not mediated by alterations in transmembrane Na{sup +} and Ca{sup 2+} gradients and could not be blocked by prior inhibition of plasma membrane Na{sup +},K{sup +}-ATPase. Hg{sup 2+} did not increase (Ca{sup 2+}){sub i} regardless of the (Ca{sup 2+}){sub o}. There was no increase in the leakage of lactate dehydrogenase but ({sup 3}H)deoxyglucose-6-phosphate (({sup 3}H)dgluP), fura-2, and {sup 45}Ca{sup 2+} efflux were all elevated by Hg{sup 2+}. There was also a Hg{sup 2+}-induced increase in intrasynaptosomal fura-2 quenching by Mn{sup 2+}. Taken together, these data suggest that Hg{sup 2+} increased the permeability of the plasma membrane to small molecules but not to larger ones. The efflux of ({sup 3}H)dgluP and {sup 45}Ca{sup 2+} was not altered by Co{sup 2+} which effectively blocked all the Hg{sup 2+}-induced increase in ({sup 3}H)dopamine release. Cd{sup 2+} and Pb{sup 2+} were ineffective in blocking this effect suggesting that Hg{sup 2+} does not interact with voltage-dependent Ca{sup 2+} channels to increase spontaneous ({sup 3}H)dopamine release. The Hg{sup 2+} chelator, dimercaptosuccinic acid, was only marginally more effective in reversing Hg {sup 2+}-induced ({sup 3}H)dopamine release than washing in Hg{sup 2+}-free buffer and suggests that Hg{sup 2+} may act at intrasynaptosomal sites, presumably at or near transmitter release mechanisms. Pb{sup 2+}, which is thought to have direct actions on transmitter release from synaptosomes, produced a biphasic increase in spontaneous ({sup 3}H)dopamine release that was not blocked by Co{sup 2+}.

• Research Organization: Cincinnati Univ., OH (United States)
• OSTI ID: 5657388
• Country of Publication: United States
• Language: English

Related Subjects

550201 -- Biochemistry-- Tracer Techniques
560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ACID ANHYDRASES
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
AMINES
ANIMAL CELLS
ANIMALS
AROMATICS
ATP-ASE
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOLOGICAL EFFECTS
CALCIUM COMPOUNDS
CARDIOTONICS
CARDIOVASCULAR AGENTS
CELL CONSTITUENTS
CELL MEMBRANES
DOPAMINE
DRUGS
ELEMENTS
ENZYMES
HYDROGEN COMPOUNDS
HYDROLASES
HYDROXY COMPOUNDS
IN VITRO
INHIBITION
ISOTOPE APPLICATIONS
MAMMALS
MEMBRANE TRANSPORT
MEMBRANES
MERCURY
METALS
NERVE CELLS
NEUROREGULATORS
ORGANIC COMPOUNDS
PHENOLS
PHOSPHOHYDROLASES
POLYPHENOLS
RATS
RODENTS
SECRETION
SODIUM COMPOUNDS
SOMATIC CELLS
SYMPATHOMIMETICS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES