EFFECTS OF PERFUSION MEDIA ON THE Ca++ AND Mg++ CONTENT OF RAT LIVER

Normal adult male rats were injected with 45CaCl2 intraperitoneally, and radioactivity in whole blood and liver was assayed at intervals of 10 minutes to 48 hours; the results showed rapid equilibration of 45Ca in the liver. In different animals, hepatic perfusion was carried out 4 hours after intraperitoneal injection of 45CaCl2. Portal perfusion with 100 ml of Krebs–Ringer phosphate (KRP) solution removed over 90% of the 45Ca from the liver, and addition of 0.5% EDTA to the solution did not alter the amount removed, although it resulted in earlier 45Ca washout. In other groups of rats, Ca++ and Mg++ concentrations were measured by atomic absorption spectrophotometry in samples of unperfused liver, and livers perfused with various media. Perfusion with KRP had little effect, but KRP + EDTA removed 60% of the Ca++ and 10% of the Mg++, whereas Ca++- and Mg++-free KRP removed 76% of the liver Ca++ but only 4% of the Mg++. It is concluded that tissue Ca++ is extremely loosely bound, and that EDTA effects on cell adhesion and permeability are due primarily to removal of tissue Ca++.