Submitted to: Journal of Nutritional Immunology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/1/1997
Publication Date: N/A
Citation: Interpretive Summary: Vitamin A is essential for assuring normal physiological functions in young, growing animals. Many of the important biological effects of vitamin A are mediated by retinoic acid, a product resulting from the breakdown of vitamin A in the body. Retinoic acid has been shown in rodents and humans to affect directly the function of the immune system and enhance resistance to diseases caused by infectious agents such as bacteria. One form of retinoic acid, referred to as 13-cis-retinoic acid, has been shown to be less toxic than other forms and also serve as a pool for more biologically active forms of retinoic acid. The purpose of the present study was to evaluate retinoic acid levels and the composition of immune cell populations in the blood of one-month-old calves given 13-cis- retinoic acid orally. Oral supplementation of young calves caused a significant elevation in the concentration of several different forms of retinoic acids in the blood as well as changes in the composition of the population of immune cells in the blood. No adverse effects of the treatment were observed. Additional research is needed to determine if these changes in the immune system of the young, growing calf are linked to increased resistance to infectious agents.
Technical Abstract: Ten calves were assigned to treatments to evaluate effects of oral administration of 13-cis-retinoic acid on plasma retinoids, composition of blood mononuclear leukocyte populations, and serum Ig. Treatments were control (1 ml vegetable oil, n=5) and 100 mg 13-cis-retinoic acid in 1 ml vegetable oil (n=5) per day for 5 consecutive days. Blood samples were collected for 3 days prior to beginning treatment, and 3 days weekly for 6 weeks thereafter. Administration of 13-cis-retinoic increased plasma concentrations of 13-cis-, all-trans-, and 9,13-di-cis-retinoic acid during the treatment period compared to control calves. The mean plasma retinol in treated calves was lower than in control calves (190 and 223 ng/ml, respectively). The proportion of monocytes from blood mononuclear leukocytes was decreased by oral administration of 13-cis-retinoic acid. Serum IgM and IgG concentrations were unaffected by treatment. Overall, oral administration of 13-cis-retinoic acid to calves altered plasma retinoid concentrations and proportions of mononuclear leukocytes without affecting serum IgM and IgG. Lower plasma retinol in calves fed 13-cis- retinoic acid compared to control calves may indicate a sparing mechanism of 13-cis-retinoic acid for retinol.