Characterization of the triphenyltin-induced increase in intracellular Ca2+ of mouse thymocytes: comparison with the action of A23187.
The properties of triphenyltin (TPT) in increasing intracellular Ca2+ ([Ca2+]i) of thymocytes was studied, in comparison with those of A23187, by the use of fluorescent dyes to monitor membrane potential and [Ca2+]i. Both 1 microM TPT and 30 nM A23187 increased the [Ca2+]i associated with the hyperpolarization mediated by Ca(2+)-dependent K+ conductance. The time course for the TPT-induced increase in the [Ca2+]i was much slower than that of A23187. When the external Ca2+ ([Ca2+]o) was removed, TPT produced a slight, but persistent, increase in the [Ca2+]i while A23187 caused only a transient increase in the [Ca2+]i. Reintroduction of Ca2+ to the external solution produced an increase in [Ca2+]i in both cases. Therefore, these results suggested that the increase in the [Ca2+]i of thymocytes induced by TPT and A23187 was dependent on the presence of [Ca2+]o and an intracellular Ca store. The potency of TPT in increasing the [Ca2+]i was greater than those of diphenyltin and monophenyltin, suggesting an involvement of the lipophilic property of organotins in increasing [Ca2+]i. The TPT-induced increase in the [Ca2+]i may be partly responsible for the toxicity of TPT on organs and/or organ systems.
Oyama
Y
Y
Department of Health Science, Faculty of Integrated Arts and Sciences, University of Tokushima, Japan.
Chikahisa
L
L
Noda
K
K
Hayashi
H
H
Tomiyoshi
F
F
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D005453:Fluorescence; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009947:Organotin Compounds / Q000494:pharmacology*; D010777:Photochemistry; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*
D009947:Organotin Compounds; D000001:Calcimycin; C030665:triphenyltin; D002118:Calcium