Effects of
glycerol on the state of water in edematous brain tissues were studied by the pulse FT NMR technique. Brain edemas were induced experimentally by
cold injury and triethyl
tin (TET) intoxication in Wistar rats. Ten percent w/v
glycerol (1 g/kg
body weight) were injected intravenously at 30 minutes before
decapitation for the NMR measurements. Transverse relaxation times (T2) in the cerebral gray and white matter were measured by Meiboom-Gill pulse sequence at the resonant frequency of 100 MHz. Water content was calculated from the difference between wet and dry weight after heating in an oven at 95-100 degrees C for 72 hours after the NMR measurements. In the normal brain T2 value was 76.4 msec and 75.4 msec in the gray and white matter respectively. In the edematous brain, T2 separated into two components, one slow and one fast, corresponding with the increase of water content. Values of the slow component (slow T2) were characteristic of both types of
brain edema. In the
cold injury edema, slow T2 values became 105 msec in the gray matter and 96 msec in the white matter, while in the TET induced
edema, it became 450 msec in the white matter. After
glycerol infusion, slow T2 became faster in these regions in both types of
brain edema, showing 92.1 msec in the gray matter and 88.1 msec in the white matter of the
cold injury edema, and 388 msec in the white matter of TET induced
edema. The degree of the changes of slow T2 values per unit change of water content was greater in the
cold injury edema than in the TET induced
edema. Serum osmolality elevated 23.8 mOsmol greater than the control value after
glycerol infusion in this experiment. It is concluded from these findings that
glycerol retracts free mobile water molecules from the
edema fluid by osmotic pressure gradient.