Triphenyltin-induced increase in the intracellular Ca2+ of dissociated mammalian CNS neuron: its independence from voltage-dependent Ca2+ channels.
To test the possibility that triphenyltin (TPT) increases the intracellular Ca2+ ([Ca2+]i) in neurons as found previously in thymocytes, the effect of TPT on [Ca2+]i was examined in rat cerebellar neurons by a flow-cytometer with fluorescent dyes. TPT at concentrations ranging from 3 x 10(-7) M to 1 x 10(-5) M dose-dependently increased the [Ca2+]i. The TPT-induced increase in [Ca2+]i was not attenuated by a Ca2+ channel blocker, suggesting that it was not dependent on voltage-dependent Ca2+ channels. As the concentration of external Ca2+ ([Ca2+]e) increased, TPT produced a more profound increase in the [Ca2+]i. However, the increase in the [Ca2+]i by TPT was observed even in nominally [Ca2+]e-free solution. These results suggest two possibilities. First, TPT may promote Ca(2+)-influx to the neuron. Secondly, TPT may affect the intracellular Ca-store sites. This study is relevant to the neurotoxicity of organotins because it has become progressively clear that sustained increases in the [Ca2+]i can activate various Ca(2+)-dependent degradative processes.
Oyama
Y
Y
Department of Health Sciences, Faculty of Integrated Arts and Sciences, University of Tokushima, Japan.
Chikahisa
L
L
Hayashi
A
A
Ueha
T
T
Sato
M
M
Matoba
H
H
D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D002118:Calcium / Q000032:analysis*; D015220:Calcium Channels / Q000187:drug effects*; D002531:Cerebellum / Q000187:drug effects; D009474:Neurons / Q000737:chemistry; D009947:Organotin Compounds / Q000494:pharmacology*; D051381:Rats
D015220:Calcium Channels; D009947:Organotin Compounds; C030665:triphenyltin; D002118:Calcium