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

Abstract

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.

Oxygen-17 NMR spectroscopy: Basic principles and applications (part II)

“…The enhanced T À1 1 rate in muscle was attributed to rapid exchange between free and bound molecules at H 2 O [981]. A similar loss of non-exponential T 1 relaxation was noted in analogous experiments on rat lymphocytes when the cells became necrotic [982]. These studies indicated that the non-exponential T 1 relaxation behaviour in muscle was not simply a result of the orientation of myofibrils causing anisotropic effects.…”

“…Necrosis presumably causes a destruction of the nuclear membrane, and, thus, mixing of the different compartments of H 2 O within the tissue which results in a single population of H 2 O. Temperature reduction affects both T 1 values equally suggesting that transmembrane transport exchange does not make a significant contribution to relaxation in this system [982]. 17 O and 1 H NMR was utilized to investigate the relaxation rates for aqueous suspension of dark adapted chloroplasts in the presence of Mn 2+ [983a].…”

“…Two-thirds of the water relax slowly (T 1 = 5.1 ms) and identified with the cell nucleus, whereas the fast relaxing (T 1 = 3.1 ms) fraction was identified with the cytoplasm [982]. Lowering the Larmor frequency by 41% (7.72 MHz to 4.36 MHz) reduces T 1 of the fast component by % 12% without affecting the slow component.…”

“…O from H2 17 O in malignant rat ghymocytes were found to be reduced compared to normal rat ghymocytes[982].Collections of T 1 ( 17 O) and T 2 ( 17 O) data in biological tissues have been made by Beall et al [986]. Lauterwein et al [987] investigated 17 O NMR relaxation times of water in the serum of rats with various cancers.…”

17O MRS assesses the effect of mild hypothermia on oxygen consumption rate in tumors

“…Although 17 O nuclear magnetic resonance (NMR) spectroscopy has been utilized for a long time in the life sciences, modern instrumentation has allowed the development of both 17 O magnetic resonance spectroscopy (MRS) and 17 O magnetic resonance imaging (MRI) . During oxidative metabolism, molecular oxygen is converted into water at a rate dependent on the metabolic activity in tissues.…”