CS-133 RELAXATION-TIMES IN RAT-TISSUES

Cs-133 relaxation-time studies of tissues from rats into which cesium has been incorporated by dietary loading have been carried out in vivo and in vitro. Whereas tissue T-1 values are on the order of seconds, T-2 values are as low as a few tens of milliseconds, Cs-133 tissue rel axation times are analogous to those of K-39 in the same tissues, but are more readily measured because of the greater sensitivity of Cs-133 compared with K-39, T-1 and T-2 data of excised tissue at two resonan ce frequencies (65.60 and 39.37 MHz) and temperatures (302 and 278 K) have been analyzed in terms of a general description of spin-7/2 relax ation. The results are consistent with most of the cesium ions being i n a free state, undergoing fast exchange with bound ions having long c orrelation times located in one or more intracellular compartments, (C ) 1995 Academic Press, Inc.