EFFECT OF SODIUM CHLORIDE ON BEEF LIVER MAO DURING STORAGE IN FROZEN STATE

Abstract

The effect of medium in homogenate on the stability of MAO in beef liver was studied. For the measurement of MAO activity, modified benzylamine method of McEwen was employed.
When 1, 000 times diluted homogenate of beef liver was made with 0.25M sucrose or pure water and it was stocked at -20°C for one week, no change in MAO activity was observed. However, when the homogenate was made with physiological saline, a marked decrease in MAO activity was found. In this case, 0.25 M sucrose was added to saline, no change in MAO activity was observed. The decrease in MAO activity with physiological saline was affected by the rate of dilution of the homogenate. When it was diluted 4 times or 10 times, the change in MAO activity was not occured. However, the MAO activity was decreased to 56% and 27% of the control value when it was diluted 100 times and 1, 000 times, respectively. The rate of decrease in MAO activity in case of 1, 000 times diluted homogenate was also changed with the concentration of NaCl in medium. When the concentration of NaCl in medium was under 0.03%, no decrease in MAO activity was detected. However, when the concentration of NaCl in medium was 0.1%, 0.3% and 0.1%, the MAO activity was decreased to 50%, 25% and 15% of the control value, respectively. The decrease in MAO activity by saline was not changed with the pH in the homogenate. The decrease in MAO activity by physiological saline during stock in deep freezer was also occured in the case of MAO in beef brain but was not occured in the case of MAO in beef serum. The decreased MAO activity with the physiological saline during stock at -20°C for one week was not recovered by dialysis against pure water over night at 4°C.
From these data, it was suggested that some irreversible changes in enzyme protein of MAO in beef liver might be produced by the saline during stock in deep freezer for one week.