Effect of electrical stimulation on IGF-1 transcription by L-type calcium channels in cultured retinal Müller cells.
OBJECTIVE
To investigate the effect of electrical stimulation (ES) on the induction of insulin-like growth factor 1 (IGF-1) in cultured retinal Müller cells.


METHODS
Müller cells were isolated from rat retinas. ES was applied to Müller cells of passage 1 with biphasic pulses (duration, 1 ms; frequency, 20 Hz; current, 0-10 mA) for 30 min. The mRNA level of IGF-1 was determined by reverse transcription-polymerase chain reaction (RT-PCR) immediately to 2 h after ES. The change of intracellular calcium concentration ([Ca(2+)]) induced by ES was monitored by Ca(2+) imaging with Fura 2-AM. Ca(2+) imaging and RT-PCR were performed with and without the application of l muM nifedipine, an L-type calcium channel blocker.


RESULTS
The mRNA level of IGF-1 was increased significantly (P<0.05) by about 1.3-fold immediately after 10 mA ES. [Ca(2+)] began to increase immediately after the start of ES, reached a maximum of approximately 1.8-fold, and continued to increase until about 20 min after the ES. The inductions of IGF-1 transcription and Ca(2+) influx were suppressed by nifedipine.


CONCLUSIONS
These results indicate that the enhancement of IGF-1 transcription by ES in cultured Müller cells depends largely on Ca(2+) influx through L-type Ca(2+) channels.
Sato
Tatsuhiko
T
Department of Applied Visual Science, Osaka University Medical School, Osaka, Japan.
Fujikado
Takashi
T
Department of Applied Visual Science, Osaka University Medical School, Osaka, Japan. fujikado@ophthal.med.osaka-u.ac.jp.
Morimoto
Takeshi
T
Department of Ophthalmology, Osaka University Medical School, Osaka, Japan.
Matsushita
Kenji
K
Department of Ophthalmology, Osaka University Medical School, Osaka, Japan.
Harada
Takayuki
T
Department of Molecular Neurobiology, Tokyo Metropolitan Institute for Neuroscience, Tokyo, Japan.
Tano
Yasuo
Y
Department of Ophthalmology, Osaka University Medical School, Osaka, Japan.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002478:Cells, Cultured; D004558:Electric Stimulation; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008856:Microscopy, Fluorescence; D009457:Neuroglia / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D012160:Retina / Q000166:cytology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D009543:Nifedipine; D002118:Calcium