닭에 過量給與한 vitamin A의 體內代謝에 미친는 影響에 關한 硏究

Effect of excess feeding of vitamin A on the metabolic influence of vitamin A in chicks

Studies were conducted to obtain information about the effects of excess feeding of vitamin A on metabolic influence of vitamin A in growing chicks. 32 vitamin A depleted chicks, 7 week old, fed for 27 days on vitamin A free diet which contained 19.94mg of carotenoid per kg of diet as the only source of vitamin A, were divided into 4 groups each of which comprised 8 chicks. The chicks in each group were supplemented with 10,000,100,000,500,000, and 1,000,000 I.U. of vitamin per kg of diet, respectively. In order to identify the elevation of vitamin A level plasma vitamin A levels of each group were estimated in 1 week interval during 27 days. On the 27th days of the study when the chicks maintained fairly constant levels of elevated plasma vitamin A, the chicks were killed. Prior to their killing, their blood were collected from the heart and centrifuged to get oxalated plasma. The livers were flushed with 0.9% NaCl solution and weighed. The plasma and liver samples were stored at-20℃ until the samples were analyzed. The following results were obtained in these experiments and summarized as follows: 1. Excessive supplement of vitamin A in the range of 100.000-1,000,000 I.U. to chicks had no apparant toxic effect and the chicks maintained normal growth rates until the end of the study. 2. Significant changes in the plasma protein levels in reponse to excessive intakes of vitamin A were not observed in chicks. 3. Excessive intakes of 100,000 I.U. of vitamin A per kg of diet resulted in a large elevation of plasma lipid content, 617.01mg/100ml, but further excessed doses of 500,000 and 1,000,000 I.U. of vitamin A per kg of diet caused the marked diminution of plasma lipid levels, to 493.15mg and 340.45mg/100ml, respectively. 4. The differences in red blood cell fragility were not found between normal chicks and hypervitaminotic chicks fed on 100,000 I.U. of vitamin A per kg of diet, but a slight increase of 5% (from 3.43% to 8.49%) hemolysis was observed in the groups fed on 500,000-1,000,000 I.U. per kg of diet. 5. Plasma inorgainc phosphorus levels were decreased by excessive administration of vitamin A, but the activities of plasma alkaline phosphatase remained fairly constant. 6. Slight increases of liver weight were observed in chicks which were hypervitaminotic, even though plasma protein and lipid remained in normal levels. This may suggest that the proliferation of parenchymal tissue cell caused increase of liver weight.