DEPENDENCE OF GROWTH, BONE METABOLISM AND FUNCTIONS OF POLYMORPHONUCLEAR LEUKOCYTES ON ASCORBIC-ACID IN PIGS

Pigs with hereditary ascorbate deficiency (OD pigs) were depleted of; or supplemented with, ascorbic acid by respective diets. Depletion of young (i.e. 5-7 weeks old) animals for at least three weeks had a nega tive effect on growth, body temperature and levels of bone alkaline ph osphatase and induced symptoms of scurvy. Doses of 5 mg ascorbic acid kg(-1) body weight day(-1) were sufficient to reverse these effects. T he level of ascorbic acid sharply decreased in plasma within one week of depletion, whereas in leukocytes it declined more slowly and to a l ower extent, Bone alkaline phosphatase levels substantially declined i n ascorbic acid depleted animals. Supplementation with > 100 mg ascorb ic acid kg(-1) body weight day(-1) did not improve growth, Dietary asc orbic acid was absorbed from the intestinal lumen into the blood withi n less than I hour and reached a peak 5-6 hours after the meal. The ex tent of this absorption depended on the systemic ascorbic acid level. Ascorbic acid influenced leukocyte function, since the production of r eactive oxygen intermediates by polymorphonuclear leukocytes decreased in supplemented animals. Thus, this animal model permits to establish the level of dietary ascorbic acid that is critical for growth of pig s as well as to study its absorption into the blood and the associated alterations in polymorphonuclear leukocytes and bone metabolism.