THE EFFECT OF CALCIUM CONCENTRATION ON THE PROTHROMBIN TIME OF DOGS TREATED WITH DICUMAROL

Abstract

The clotting time and prothrombin time with whole blood, and the clotting time and prothrombin time of oxalated plasma on addition of various concs. of Ca, were detd. on dogs treated with dicumarol. Normal plasma gave very little variation in prothrombin time with Ca cones, from 0.005-0.10 M. Dicumarol plasma shows a definite optimal Ca cone, of 0.025 M and concs. above and below this value gave very much longer clotting times. The difference between these times and those with optimal Ca conc. increased up to the peak of the dicumarol effect and decreased as the prothrombin returned to its normal level. This effect of Ca on dicumarol plasma is not duplicated by diluting normal plasma to give the same prothrombin time with 0.025 M Ca. Differences between sp. were observed regarding the effect of varying Ca cone, on normal prothrombin time. Ca conc. has an even more marked effect on the plasma clotting time. The blood prothrombin time in a highly dicoumarized animal can be reduced by adding more Ca.