Date of Award
Doctor of Philosophy
Zoology and Genetics
M. Duane Enger
The main purpose of this work was to examine how cadmium modifies cell growth and specific gene expression in normal rat kidney fibroblast cells;It was found that cadmium inhibits EGF-induced DNA synthesis, but not myc mRNA accumulation and amino acid incorporation;To further study cadmium's function in these cells, clonal subpopulations were isolated from NRK-49F NM cells. It was found that subclones N1 and N4 show opposite responses to TGF-beta and they also have different cadmium sensitivities. Thus, a subclone N1 which shows highest cadmium sensitivity and also TGF-beta sensitivity in inhibiting EGF-induced DNA synthesis was chosen for further study in a defined passage range;Through comparison of N1 cells with their parent cells and from studies using flow cytometric analysis it was found that cadmium induces a hypertrophic response accompanied by increased myc mRNA accumulation in these cells, indicating that cell proliferation and cell hypertrophy may in part share common activation pathways involving myc accumulation in these cells;Cadmium mimics TGF-beta function in these cells. They both inhibit EGF-induced DNA synthesis in serum starved monolayers but not myc mRNA accumulation. Both can be added several hours later than EGF and still inhibit EGF-induced DNA synthesis, indicating that they both inhibit EGF-induced DNA synthesis at late but not early events. TGF-beta neutralizing antibody only neutralizes TGF-beta1 function but not cadmium effects. This suggests that cadmium does not function through activation or preinduction of TGF-beta;Specific genes modified by cadmium were also examined. It was found that cadmium induces delayed myc and jun accumulation, as well as both early and late fos accumulation in these NRK-49F N1 cells. The induction of these specific mRNA is insensitive to cycloheximide but sensitive to actinomycin D, and therefore, is not due to preinduction of TGF-beta or other gene-activating growth factors, but rather to direct action of cadmium, and transcription is required for cadmium induction of these oncogenes' mRNA accumulation.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Tang, Ning, "Cadmium modification of cell growth and specific gene expression in normal rat-kidney fibroblast cells " (1991). Retrospective Theses and Dissertations. 9782.