Effects of Vitamin A on Blood Coagulation and Clot-Lysis Times

The effects of dietary excess of vitamin A on one-stage prothrombin time and on one-stage euglobulin-lysis time were studied in Single Comb White Leghorn, New Hampshire, and Black Australorp chicks. Prothrombin time was increased by the feeding of 100 000 and 200 000 I.U. of vitamin A per kilogram of diet to the Black Australorp chicks but it was not increased when these amounts of vitamin A were fed to either the White Leghorn or the New Hampshire chicks. The prolongation of prothrombin time was reversed within 16 h by injection of menadione. Vitamin A at 100 000 and 200 000 I.U./kg of diet decreased euglobulin-lysis times in chicks of all three breeds but increased the concentration of fibrinogen in the plasma. The effect of excess vitamin A on euglobulin-lysis time was not associated with induced vitamin K deficiency. The decreased euglobulin-lysis time resulting from intake of excess vitamin A persisted for 6 weeks subsequent to the feeding of moderate amounts of vitamin A.