UBC Theses and Dissertations
Excess vitamin A as a factor in alimentary cholesterolemia, blood coagulation and clot lysis in the chicken Woodward, William Douglas Hiram
The physiological effects of excess vitamin A are frequently studied in the investigation of the systemic function of the vitamin. The liver vitamin A storage efficiency of dietary excesses of vitamin A and the effect of excesses of the vitamin on alimentary cholesterolemia, the one-stage prothrombin time and the one-stage euglobulin lysis time were investigated in several genetically distinct populations of chickens. Birds of a New Hampshire (NH) line were found to store vitamin A in the liver from the diet more efficiently than birds of three White Leghorn (WL) strains (D,K and B) and of one broiler strain. An excess of dietary vitamin A reduced alimentary cholesterolemia in the NH chicks but increased alimentary cholesterolemia in the D chicks. There was no effect of hypervitaminosis A on the blood cholesterol concentration of either the D or the NH chicks receiving a low-cholesterol diet. No carryover effect of vitamin A upon removal of the excessive quantity of the vitamin from the diet, could be demonstrated on alimentary cholesterolemia in either the D or the NH chicks. The efficiency of the intestinal absorption ofcholesterol was increased in both the NH and the D chicks by an excess of vitamin A. The liver-to-blood partition ratio of cholesterol was increased by excess vitamin A administration in the NH chicks, but was decreased by excess vitamin A in the D chicks. The one-stage prothrombin time of D,K,B, and NH chicks was unaffected by the dietary administration of large excesses of the vitamin from day-old to three weeks of age. Chicks of a Black Australorp (A) line, however, responded to large excesses of the vitamin in the diet with an increase in one-stage prothrombin time. A single intramuscular injection of menadione (5 mg/kg body weight) brought the prolonged prothrombin times of the A chicks to normal within twenty hours. The one-stage euglobulin lysis time of NH,D and A chicks was decreased by the inclusion of large excesses of vitamin A in the diet of the birds from day-old to six weeks of age. Intramuscular administration of menadione (5 mg/kg body weight) was without effect on the shortened lysis times within twenty-four hours. Removal of the excessive quantities of vitamin A from the diet for six weeks failed to affect the shortened clot lysis times of the A hypervitaminotic chicks. Vitamin K deficiency induced in a Shaver strain of WL chicks by feeding the birds a K-deficient diet, had no effect on the euglobulin lysis time. The results of the present experiments extend knowledge of the effects of hypervitaminosis A on the induction of alimentary cholesterolemia and on the blood coagulation mechanism in the chicken.
Item Citations and Data