AN INVESTIGATION OF RAT MAMMARY HEALTHY AND R3230AC TUMOR-TISSUES ANDCELLS BY MEANS OF SOLID-STATE C-13 NMR

The first results are shown of a low temperature C-13 solid-state, cro ss-polarization magic angle spinning (CPMAS) NMR study of R3230AC rat mammary carcinoma transplanted into female Fischer rats. Intact, healt hy mammary tissues and tumor tissues, quickly frozen at -78 degrees C after excision, were examined, as were normal epithelial cells and tum or cells extracted from these tissues. The experiments were performed at -100 degrees C and -40 degrees C. The solid-state C-13 NMR spectrum of the healthy tissue is dominated by the triacylglycerols present in the adipose tissue. The solid-state spectra of the other compounds di ffer significantly from the spectrum of the healthy tissue, and are do minated by the phospholipids and the large molecular weight proteins, for a major part present in the membranes. The spectra of the tumor ti ssues and the tumor cells were very similar, in accordance with the fa ct that the tumor tissues consisted of 80-90% tumor cells. The spectru m of the normal cells shows the same general features as those of the tumor tissue and tumor cells, but also exhibits some significant diffe rences. The main difference at -100 degrees C is that, in the tumor sa mples, the relative intensity of the resonance line arising at 30 ppm, which is due to methylene chains, is reduced. At -40 degrees C this i ntensity is futher reduced in the tumor samples, whereas the spectrum of the normal cells remains unaltered. It is tentatively concluded tha t the spectral differences between the normal and the malignant cells are due to changes in mobilities occurring in the cells after tumorige nesis, and that compared with normal epithelial cells the tumor cells contain an increased amount of mobile methylene chains. These differen ces virtually disappear if the samples are preserved at temperatures e qual to or above 4 degrees C, emphasizing the importance of sample pre servation at low temperatures, and hence of the solid-state NMR approa ch to investigate structures and dynamics in cells before and after tu mor formation.