Effect of hematoporphyrin derivative (HPD) plus light on transcription activity in the nucleus
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To elucidate the mechanism of photodynamic damage of cells, the effect of HPD plus light on transcriptional ectivity in the mucleus isolate from the normal rat liver was studiedin vitor by3H- UTP incorporation into RNA. Measurements of fluorescence spectrum showed that HPD was bound to the nucleus and its fluorescence intensity increased with the increase of HPD concentration. The experimental results indicated that no changes could be observed when either HPD or light was used alone. Whereas the nuclear transcription activity was found to be inhibited significantly by both HPD and light treatment, and the degree of inhibition was dependent on the HPD concentration and the time of exposure to light. After treatment by 3 µg/ml HPD, the inhibition rate of the nuclear transcription activity was 23%, 45%, 69%, 80% and 90%, respectively for light exposure of 2, 5, 10, 20 and 30 minutes. Our results suggested that dose-dependent decreases in the nuclear transcription activity, and marked inhibition of the activity was found in the range from 3 to 7 µg/ml HPD following exposure to light.
KeywordsFluorescence Spectrum Transcription Activity Light Treatment Hematoporphyrin Hematoporphyrin Derivative
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