NUCLEAR-MAGNETIC-RESONANCE STUDY OF LUNG WATER COMPARTMENTS IN THE RAT

Nuclear magnetic resonance transverse relaxation time (T2) was previou sly measured in studies of lung water. The T2 decay curves for periphe ral lung tissue were found to be multiexponential with two T2 componen ts: T2 fast (T2f) and T2 slow (T2s). This behavior was explained by th e compartmentalization of water, in which the protons of water are res tricted and do not undergo rapid exchange between the compartments. We investigated the origin of the water for these T2 components using ex cised rat lungs. The effect of magnetic field inhomogeneity due to air -tissue interfaces was examined by degassing some lungs. The contribut ion of intravascular water was examined by perfusing the lungs with oi l or NaCl solutions. Degassing produced a greater increase in the T2f than the T2s component, indicating that the water in the alveolar wall s exposed to air spaces contributed to the T2f. Perfusion with oil dec reased the T2s, indicating that intravascular water contributed to the T2s component. The effects of intravascular osmotic pressure on the T 2f and T2s components suggest that intracellular water is related to t he T2f component.