Pulsed nuclear magnetic resonance study of 17-O, 2-D, and 1-H of water in frog striated muscle

Whole gastrocnemius muscles were incubated in Ringer's solution enriched with H2–17O; the paired contralateral gastrocnemius muscles were incubated in a similar solution enriched with deuterons, as well. Subsequently, the longitudinal relaxation times (T1) were measured 17-O, 2-D, and 1-H, both at 8.1 MHz and at 4.3 MHz. The results indicate that: (a) the absolute values of T1 characterizing the three nuclides are different in muscle and pure water. (b) the longitudinal relaxation rates of all three have an identical frequency dependence over the range studied, (c) the ratio (T1)2D/(T1)17ois the same in muscle water and pure water, while the ratio (T1)1H/(T1)17o is 2.1 times greater in pure water than it is in muscle water, and (d) 30–49 percent substitution of 2-D for 1-H has very little effect on the spin-lattice relaxation of tissue water protons. These data suggest that muscle water is in rapid exchange between a small fraction of immobilized molecules and a large fraction of free water. The results render unlikely the possibility that hypothetical ordering of muscle water significantly contributes to its longitudinal relaxation