An investigation into the mechanism of the in vitro fall in rabbit plasma calcium which follows intravenous heparin injection

Abstract

Experiments were carried out on plasma obtained from rabbits, injected intravenously with heparin, to examine the cause of the fall in plasma calcium which occurs in vitro under these circumstances when calcium is estimated by direct EDTA titration. The fall in plasma calcium is accelerated by the addition of chyle to plasma, and is accompanied by a decrease in optical density and a rise in FFA concentration of the plasma. Where the fall in optical density, or the rise in FFA concentration, is prevented or reduced, the fall in plasma calcium is stopped or slowed down. A linear relationship was found between the fall in plasma calcium and FFA concentration which was statistically highly significant. A rise of 1 μequiv FFA above a threshold value of I μequiv FFA/ml lowered plasma calcium by 0.5 μuequiv/ml.