Effect of 72 Hz pulsed magnetic field exposure on ras p21 expression in CCRF-CEM cells.
CCRF-CEM T-lymphoblastoid cells have been exposed to an asymmetric electromagnetic signal pulsed at 72 Hz for up to 28 hr. Following exposure, cells were lysed and extracted, and the extract was electrophoresed on SDS-polyacrylamide gels. Proteins were electroblotted onto nitrocellulose membranes and the product of the ras proto-oncogenes, p21, was identified and quantitated by successive treatment with pan ras p21 antibody, second antibody-alkaline phosphatase conjugate, and enzyme substrate. No changes in p21 levels were observed for the first 6 h of electromagnetic field exposure as compared to unexposed control cells. However, from 6-16 h exposure, p21 levels in exposed cells decreased linearly to only 30% of control values. From 16-28 h exposure, p21 levels in exposed cells increased nearly linearly to control cell values. Slot-blot analysis indicated that altered p21 protein expression is a result, at least in part, of changes in the levels of N-ras mRNA. No concomitant changes were detected in either cyclic AMP levels or in the expression of cell surface markers. While the significance of the marked reduction in cellular p21 is unclear, it does not appear to be related to cell differentiation.更多