Accumulation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in cultured cerebellar astrocytes.
Cultured cerebellar astrocytes rapidly accumulate 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) from the incubation medium, reaching a plateau within 10 min, whereas within that time negligible amounts of 1-methyl-4-phenylpyridinium (MPP+) have entered the astrocytes. MPTP accumulation is essentially independent of temperature and is proportional to extracellular concentration at steady state: The steady-state concentration achieved within these cells is about 50-fold higher at relatively low extracellular concentrations. MPTP appears to accumulate intracellularly within lysosomes, because lysosomotropic agents such as ammonium chloride and chloroquine markedly diminish the accumulation. Moreover, a proton gradient is required, because MPTP accumulation is abolished by the hydrogen ion antiporter monensin. Over an interval of several days, MPTP is converted to MPP+ intracellularly, with a concomitant decrease in medium MPTP and increase in medium MPP+. A constant, small but significant amount of MPP+ is retained intracellularly over a 72-h interval. Increasing the medium MPTP concentrations results in increased conversion of MPTP and enhanced intracellular retention of MPTP and MPP+. Neither MPTP nor MPP+ is neurotoxic to cultured cerebellar astrocytes as determined by cell counts and rate of conversion of MPTP to MPP+.
Marini
A M
AM
Clinical Neuroscience Branch, NINDS, National Institutes of Health, Bethesda, Maryland 20892.
Lipsky
R H
RH
Schwartz
J P
JP
Kopin
I J
IJ
D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000378:metabolism* / Q000494:pharmacology; D015655:1-Methyl-4-phenylpyridinium / Q000378:metabolism; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D002738:Chloroquine / Q000494:pharmacology; D008247:Lysosomes / Q000187:drug effects
D000643:Ammonium Chloride; D002738:Chloroquine; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D015655:1-Methyl-4-phenylpyridinium