Tatsuhiko Sato1, Takashi Fujikado2, Takeshi Morimoto3, Kenji Matsushita3, Takayuki Harada4, Yasuo Tano3. 1. Department of Applied Visual Science, Osaka University Medical School, Osaka, Japan. 2. Department of Applied Visual Science, Osaka University Medical School, Osaka, Japan. fujikado@ophthal.med.osaka-u.ac.jp. 3. Department of Ophthalmology, Osaka University Medical School, Osaka, Japan. 4. Department of Molecular Neurobiology, Tokyo Metropolitan Institute for Neuroscience, Tokyo, Japan.
Abstract
PURPOSE: 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.
PURPOSE: 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.
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