Some blood coagulation studies in normal and scorbutic guinea -pigs

Abstract

Male guineapigs of 250 g. bodyweight were fed until they reached a weight of 300 g. on the semisynthetic diet of Reid and Briggs (Abst. 3515, Vol. 24), with vitamins A, D, E and K given separately; the diet contained 2 g. ascorbic acid per kg. and the normal intake was from 50 to 70 mg. daily. Thereafter one group had for from 17 to 23 days the diet without ascorbic acid, on which food intake and weight fell after from 10 to 12 days; another continued on the complete diet; and others, after 10 days without ascorbic acid, had 0.4, 0.8, or 1.6 mg. ascorbic acid daily, or the same total amounts given 2 or 3 times a week instead of daily, in 1 per cent. citric acid, for 3 months. These supplements gave, respectively, no, retarded and normal growth. Under ether anaesthesia blood was collected from the vena cava without contact with glass; some was allowed to clot at 37o C. and some was citrated. In scurvy, clot retraction and lysis appeared normal. Whole-blood platelet count was greatly increased. One-stage prothrombin time of plasma measured by Quick's method was increased, but not Stypven time measured with Russell viper venom in presence of lipid. Thromboplastin activity, measured by the method of Bell and Alton (Nature, 1954, 174, 880) was reduced. Further tests showed that the coagulation defects were found in both serum and plasma; their exact nature was not elucidated. Impairment of prothrombin and thromboplastin was prevented by 0.8 mg. ascorbic acid in the diet daily, but not by intramuscular injection of ascorbic acid 1 hr. before blood was taken, or by addition of ascorbic acid to plasma in vitro, so that the effect of ascorbic acid is not a direct one. Intramuscular injections of vitamin K for several days beforehand had no effect either. The animals with scurvy all had small haemorrhages in muscles around the knees and some in the viscera, but whether they were related to the coagulation defects was not clear.-W. M. Deans.