H-1 MR VISIBLE LIPIDS IN COLON TISSUE FROM NORMAL AND CARCINOGEN-TREATED RATS

Metabolic characteristics of colon mucosa, submucosa, muscularis and t umour specimens from four control (n=105) and nine carcinogen (azoxyme thane)-treated (n=91) Sprague-Dawley rats were investigated by ex vivo H-1 MRS, Ninety-seven per cent of pure mucosa samples (n=59) yielded spectra with narrow lipid resonances (chemical shift delta of -(CH2)(n )-, 1.3 ppm; linewidth at half-height nu(1/2), 30-50 Hz), Eighty-two p er cent of control mucosa samples with histologically proven submucosa contamination (n=11) and 46% of control cross-sections (containing mu cosa, submucosa and muscularis; n=57) yielded spectra with broad lipid resonances (delta -(CH2)(n)-, 1.5 ppm; nu(1/2), 80-100 Hz) identical to those of adipose tissue surrounding rat colon, Thirty per cent of t umour samples (n=10) yielded spectra with narrow lipid resonances whil e 70% contained no significant amount of MR visible lipids. We conclud e that (i) lipids giving rise to broad resonances are in the heterogen eously distributed adipocytes of submucosa, (ii) lipids giving rise to narrow resonances are within the mucosa in an unknown structural envi ronment, and (iii) the type and distribution of lipids in human and ra t colon are similar, Tumours contained significantly more taurine than pure control mucosa (n=15; p<0.004) and pure mucosa containing aberra nt crypt foci (putative preneoplasm, n=36; p<0.002). Our results sugge st that the rat colon is a good model for H-1 MR investigations of hum an colon carcinogenesis.