RESUMO
The first results are shown of a low temperature 13C solid-state, cross-polarization magic angle spinning (CPMAS) NMR study of R3230AC rat mammary carcinoma transplanted into female Fischer rats. Intact, healthy mammary tissues and tumor tissues, quickly frozen at -78 degrees C after excision, were examined, as were normal epithelial cells and tumor cells extracted from these tissues. The experiments were performed at -100 degrees C and -40 degrees C. The solid-state 13C NMR spectrum of the healthy tissue is dominated by the triacylglycerols present in the adipose tissue. The solid-state spectra of the other compounds differ significantly from the spectrum of the healthy tissue, and are dominated by the phospholipids and the large molecular weight proteins, for a major part present in the membranes. The spectra of the tumor tissues and the tumor cells were very similar, in accordance with the fact that the tumor tissues consisted of 80-90% tumor cells. The spectrum of the normal cells shows the same general features as those of the tumor tissue and tumor cells, but also exhibits some significant differences. The main difference at -100 degrees C is that, in the tumor samples, the relative intensity of the resonance line arising at 30 ppm, which is due to methylene chains, is reduced. At -40 degrees C this intensity is further reduced in the tumor samples, whereas the spectrum of the normal cells remains unaltered. It is tentatively concluded that the spectral differences between the normal and the malignant cells are due to changes in mobilities occurring in the cells after tumorigenesis, and that compared with normal epithelial cells the tumor cells contain an increased amount of mobile methylene chains. These differences virtually disappear if the samples are preserved at temperatures equal to or above 4 degrees C, emphasizing the importance of sample preservation at low temperatures, and hence of the solid-state NMR approach to investigate structures and dynamics in cells before and after tumor formation.
