ADMINISTRATION OF 13-CIS-RETINOIC ACID TO DAIRY-CATTLE .1. PLASMA RETINOID CONCENTRATIONS AND LYMPHOCYTE BLASTOGENESIS

Effects of administration of 13-cis-retinoic acid on concentrations in plasma of retinoic acid isomers, retinol, and beta-carotene and on in vitro mitogen-stimulated lymphocyte blastogenesis of peripheral blood mononuclear leukocytes were evaluated in Holstein cattle. Treatments consisted of i.m. injections of 0 (vehicle only), 100, 200, or 400 mg of 13-cis-retinoic acids in dimethylsulfoxide for 7 d. Concentrations of 13-cis- and all-trans-retinoic acids in plasma and in mononuclear l eukocytes were elevated in a dose-dependent manner by administration o f 13-cis-retinoic acid. Treatment with 13-cis-retinoic acid, however, had no effect on concentrations of retinol and beta-carotene in plasma . In vitro DNA synthesis in unstimulated and mitogen-stimulated mononu clear leukocyte cultures was unaffected by in vivo administration of 1 3-cis-retinoic acid. In contrast, in vitro supplementation of unstimul ated and mitogen-stimulated mononuclear leukocyte cultures with 13-cis -retinoic acid inhibited DNA synthesis relative to unsupplemented cult ures. In conclusion, elevated plasma and intracellular concentrations of 13-cis-and all-trans-retinoic acids produced by repeated i.m. admin istrations of 13-cis-retinoic acid did not affect peripheral blood mon onuclear leukocyte function, as measured by the in vitro blastogenic r esponse of peripheral blood lymphocytes.