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-S. 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.