The Signal Transduction Mechanisms on the Intestinal Mucosa of Rat Following Irradiation

Yoo, Jeong Hyun; Kim, Sung Sook; Lee, Kyung Ja; Rhee, Chung Sik

Abstract

PURPOSE: Phospholipase C(PLC) isozymes play significant roles in signal transduction mechanism. PLC-gamma1 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 HandE stain, and the mitoses for the evidence of regeneration were counted using the light microscopy and PCNA kit. The phosphoinositide(PI) hydrolyzing activity assay was also done for the indirect evaluation of PLC-gamma1 activity.
RESULTS
In the immunohistochemistry, the expression of PLC-beta was negative for all groups. The expression of PLC-gamma1 was highest in the group III followed by group II in the proliferative zone of mucosa. The expression of PKC-sigma1 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-beta, PLC-gamma1, and PLC-sigma1 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-gamma1 mediated signal transduction including ras oncoprotein, EGFR, and PKC play a significant role in mucosal regeneration after irradiation. PLC-sigma1 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-sigma1.