| Autor: |
Hirooka K; Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia B3H 4H7., Bertolesi GE, Kelly ME, Denovan-Wright EM, Sun X, Hamid J, Zamponi GW, Juhasz AE, Haynes LW, Barnes S |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of neurophysiology [J Neurophysiol] 2002 Jul; Vol. 88 (1), pp. 196-205. |
| DOI: |
10.1152/jn.2002.88.1.196 |
| Abstrakt: |
Human retinoblastoma cells are multipotent retinal precursor cells capable of differentiating into photoreceptors, neurons, and glia. The current-voltage relation of the undifferentiated cells is dominated by a transient inward current that disappears shortly after differentiation. In 20 mM Ba(2+)-containing bath solutions, the current has an activation midpoint near -25 mV and appears to be fully inactivated at -20 mV. Sr(2+) and Ca(2+) are preferred charge carriers relative to Ba(2+), and the current vanishes in the absence of these divalent cations. Cd(2+) blocks the current with an IC(50) of 160 microM, and Ni(2+) blocks in a biphasic manner with IC(50)s of 22 and 352 microM. The current is unaffected when sodium is replaced with other monovalent cations, and it is insensitive to nifedipine, omega-conotoxin GVIA, omega-agatoxin IVA, and omega-conotoxin MVIIC. RT-PCR revealed the presence of alpha 1G and alpha 1H mRNA in undifferentiated cells, but following differentiation, a striking reduction of both alpha 1G and alpha 1H mRNA was found, and this was paralleled by the loss of T-type Ca channel currents. alpha 1I subunit mRNA levels were low in undifferentiated and differentiated cells. These results suggest that T-type Ca channels could play a role in undifferentiated retinoblastoma cell physiology since alpha 1G and alpha 1H Ca channel subunit expression is reduced in cells that have differentiated and exited the cell cycle. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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