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 acid in dimethylsulfoxide for 7 d. Concentrations of 13-cis- and all-trans-retinoic acids in plasma and in mononuclear leukocytes were elevated in a dose-dependent manner by administration of 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 mononuclear leukocyte cultures was unaffected by in vivo administration of 13-cis-retinoic acid. In contrast, in vitro supplementation of unstimulated and mitogen-stimulated mononuclear leukocyte cultures with 13-cis-retinoic acid inhibited DNA synthesis relative to unsupplemented cultures. In conclusion, elevated plasma and intracellular concentrations of 13-cis- and all-trans-retinoic acids produced by repeated i.m. administrations of 13-cis-retinoic acid did not affect peripheral blood mononuclear leukocyte function, as measured by the in vitro blastogenic response of peripheral blood lymphocytes.