Effect of a humoral factor on plasma prothrombin and vitamin K-dependent liver carboxylase levels in the rat.

Abstract

Abstract Previous reports of a possible humoral factor which regulates plasma prothrombin concentrations in the rabbit have been investigated in the rat. The administration of 0.2 ml of plasma from a vitamin K-deficient donor rat to a normal recipient rat resulted in an 18–25% increase in the plasma prothrombin (two-stage assay) within 24 hours. When plasma from a control donor was administered, there was a 5% increase in prothrombin. If prothrombin was assayed immunochemically or with E . carinatus venom, there was some increase in plasma prothrombin of recipient rats which was similar in the control and experimental groups. Donor plasma injection had no apparent effect on the rate of prothrombin degradation. Liver microsomal vitamin K-dependent carboxylase activity was significantly higher in the experimental group at 18 hours than in the control group. Donor plasma injection had no effect on the steady-state concentration or the rate of synthesis of microsomal prothrombin precursors.