CONTINUOUS MEASUREMENT OF CELL-VOLUME CHANGES IN PERFUSED RAT SALIVARY-GLANDS BY PROTON NMR

Changes in intracellular and extracellular water content have been mea sured in perfused rat salivary glands by repetitive application of an inversion recovery (IR) pulse sequence. The relaxation reagent Gd-DTPA (10 mM) was included in the perfusate so that the intracellular and e xtracellular water proton signals could be distinguished by their diff erent longitudinal relaxation times. Changes in water content in respo nse to altered perfusion pressure and perfusate osmolarity were determ ined at 30-s intervals and indicated a clear separation of the intrace llular and extracellular components. Using a modification of the IR pu lse sequence, changes in intracellular water content were also measure d at 6-s intervals. With this time resolution, differences in the rate s of cell shrinkage in response to hyperosmotic perfusates and the sec retomotor agonist acetylcholine were observed. The results suggest tha t this approach offers a relatively noninvasive method for studying ce ll volume regulation in intact, perfused tissues and organs.