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KMID : 0362919970150020079
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Journal of the Korean Society for Therapeutic Radiology and Oncology
1997 Volume.15 No. 2 p.79 ~ p.96
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The Signal Transduction Mechanisms on the Intestinal Mucosa of Rat Following Irradiation
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Yoo Jeong-Hyun
Kim Sung-Sook
Lee Kyung-Ja
Rhee Chung-Sik
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Abstract
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Purpose: Phospholipase C(PLC) isozymes play significant roles in signal transduction mechanism. PLC-γ1 is one of the key regulatory enzymes in signal transduction for cellular proliferation and differentiation. Ras oncoprotein, EGFR, and PKC are also known to be involved in cell growth. The exact mechanisms of these signal transduction following irradiation, however, were not clearly documented. Thus, this study was planned to determine the biological significance of PLC, ras oncoprotein, EGFR, and PKC in damage and regeneration of rat intestinal mucosa following irradiation.
Material and Method: Sixty Sprague-Dawley rats were irradiated to entire body with a single dose of 8Gy. The rats were divided into 5 groups according to the sacrifice days after irradiation. The expression of PLC, ras oncoprotein, EGFR and PKC in each group were examined by the immunoblotting and immunohistochemistry. The histopathologic findings were observed using H&E stain, and the mitoses for the evidence of regeneration were counted using the light microscopy & PCNA kit. The phosphoinositide(PI) hydrolyzing activity assay was also done for the indirect evaluation of PLC-γ1 activity.
Results: In the immunohistochemistry, the expression of PLC-β was negative for all groups. The expression of PLC-γ1 was highest in the group Ⅲ followed by group Ⅱ in the proliferative zone of mucosa. The expression of PKC-δ1 was strongly positive in group Ⅰ followed by group Ⅱ in the damaged surface epithelium. The above findings were also confirmed in the immunoblotting study. In the immunoblotting study, the expressions of PLC-β, PLC-γ1, and PLC-δ1 were the same as the results of immunohistochemistry. The expression of ras oncoprotein was weakly positive in groups Ⅱ, Ⅲ and Ⅳ. The of EGFR was the highest in the group Ⅱ, Ⅲ, followed by group Ⅳ and the expression of PKC was weakly positive in the group Ⅱ and Ⅲ.
Conclusion: PLC-γ1 mediated signal transduction including ras oncoprotein, EGFR, and PKC play a significant role in mucosal regeneration after irradiation. PLC-δ1 mediated signal transduction might have an important role in mucosal damage after irradiation. Further studies will be necessary to confirm the signal transduction mediating the PLC-δ1.
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KEYWORD
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Radiotherapy, Jejunal crypt cell, phospholipase C, Ras oncoprotein, EGFR PKC
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