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 negative effect on growth, body temperature and levels of bone alkaline phosphatase and induced symptoms of scurvy. Doses of 5 mg ascorbic acid kg-1 body weight day-1 were sufficient to reverse these effects. The level of ascorbic acid sharply decreased in plasma within one week of depletion, whereas in leukocytes it declined more slowly and to a lower extent. Bone alkaline phosphatase levels substantially declined in ascorbic acid depleted animals. Supplementation with > 100 mg ascorbic acid kg-1 body weight day-1 did not improve growth. Dietary ascorbic acid was absorbed from the intestinal lumen into the blood within less than 1 hour and reached a peak 5-6 hours after the meal. The extent of this absorption depended on the systemic ascorbic acid level. Ascorbic acid influenced leukocyte function, since the production of reactive 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 pigs as well as to study its absorption into the blood and the associated alterations in polymorphonuclear leukocytes and bone metabolism.