MAGNETIC-RESONANCE SPECTROSCOPY INVESTIGATIONS OF BROWN ADIPOSE-TISSUE AND ISOLATED BROWN ADIPOCYTES

Brown adipose tissue and collagenase-isolated brown adipocytes were in vestigated in rats by means of H-1 and C-13 nuclear magnetic resonance spectroscopy. After chloroform-methanol extraction of brown adipose t issue, proton and natural abundance C-13 spectra of the chloroform fra ction showed resonances attributable to triglycerides, and were qualit atively similar to those of the corresponding fraction of white adipos e tissue. By means of quantitative analysis of H-1 spectra, fatty acid unsaturation and polyunsaturation in triglycerides were found to be l ower in brown than white adipose tissue; moreover, unsaturation parame ters decreased in triglyceride fatty acids of brown adipose tissue upo n norepinephrine administration or cold acclimatization of rats, and w ere affected by the age of donors. The molar percentage of mono- and p olyunsaturated C-18 fatty acids in triglycerides was determined from C -13 spectra and found to change in the early post-natal period. Isolat ed, agarose-embedded brown adipocytes from 4-day-old rats showed a num ber of peaks in the carbohydrate region of H-1 spectra that were not p resent in spectra of white adipocytes and almost disappeared in brown fat cells of older animals. These peaks could be restored by insulin e xposure. Natural abundance C-13 spectra of isolated brown adipocytes w ere reserved enough to allow unambiguous assignment of resonances to c arbons of fatty acids, glycerol, glucose, ethanolamine, and choline. C alculation of the mono- to polyunsaturated fatty acids ratio in the ce lls was also performed. Nuclear magnetic resonance spectroscopy is a u seful tool for the investigation of brown adipose tissue and adipocyte s therefrom.