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Effects of melatonin on ionic currents in cultured ocular tissues
Ist Teil von
American Journal of Physiology: Cell Physiology, 1999-04, Vol.276 (4), p.C923-C929
Ort / Verlag
United States
Erscheinungsjahr
1999
Quelle
MEDLINE
Beschreibungen/Notizen
2 Division of Gastroenterology
and Hepatology and Departments of
1 Physiology and Biophysics and
3 Ophthalmology, Mayo Clinic and
Mayo Foundation, Rochester, Minnesota 55905
The effects of melatonin on ionic conductances in a cultured
mouse lens epithelial cell line ( -TN4) and in cultured human trabecular meshwork (HTM) cells were measured using the amphotericin perforated patch whole cell voltage-clamp technique. Melatonin stimulated a voltage-dependent
Na + -selective current in lens
epithelial cells and trabecular meshwork cells. The effects of
melatonin were observed at 50 pM and were maximal at 100 µM.
Melatonin enhanced activation and inactivation kinetics, but no change
was observed in the voltage dependence of activation. The results are
consistent with an increase in the total number of ion channels
available for activation by membrane depolarization. Melatonin was also
found to stimulate a K + -selective
current at high doses (1 mM). Melatonin did not affect the inwardly
rectifying K + current or the
delayed rectifier type K + current
that has been described in cultured mouse lens epithelial cells. The
results show that melatonin specifically stimulated the TTX-insensitive
voltage-dependent Na + current by
an apparently novel mechanism.
sodium channels; trabecular meshwork; epithelium; electrophysiology