Pulsed nuclear magnetic resonance study of 17O from H217O in rat lymphocytes

Lymphocytes obtained from thymus glands of normal rats and culture lines of malignant rat thymocytes were enriched with H217O. The longitudinal and transverse relaxations of the 17O were determined separately in samples of packed cells and supernatant solutions. The longitudinal relaxation of intracellular 17O of fresh viable lymphocytes was nonexponential, becoming simply exponential with eventual necrosis. The rate of spin-lattice relaxation (1/T1) was fitted by a sum of two exponentials. The average mole fraction of the molecules subject to the slower relaxation rate (1/T1s) was two-thirds of the total water. Lowering the Larmor frequency (omega) from 7.72 to 4.36 MHZ increased the faster component (1/T1f) by 12% without altering (1/T1s). The value of the single exponential decay of the nonviable cells was not appreciably different from the initial rate of relaxation of the fresh cells. Similar results were obtained in studies of the transverse relaxation rates. The simplest interpretation is that two-thirds of the cell water is located within the nucelus and is characterized by a slower rate of relaxation than the one-third of the cell water in the cytoplasm because of the different macromolecular compositions of the two-subcellular compartments. The malignant lymphocytes were characterized by prolonged values for the slow and fast components of both the longitudinal and transverse relaxations of 17O.