DISTRIBUTION OF RETINOIC ACID-BINDING PROTEINS IN NORMAL AND NEOPLASTIC MAMMARY TISSUES

  • 1 January 1980
    • journal article
    • research article
    • Vol. 40  (1) , 47-49
Abstract
Cellular retinoic acid-binding proteins were detected in chemically induced [rat] mammary tumors using sucrose density gradient analysis. Unlabeled retinoic acid did not displace nonspecific binding in the 5S region but was a competitive inhibitor for the specifically binding 2S component. Mammary gland cytosol fractions from 1-methyl-1-nitrosourea-treated, and untreated as well as from lactating rats, contained low levels of retinoic acid-binding proteins. 1-Methyl-1-nitrosourea treatment did not result in the increased number of binding sites. The increase in the levels of binding proteins in tumors most probably occurred during tumor development and probably was not a result of the carcinogen per se. Retinoids which were effective in the chemoprevention of mammary carcinogenesis only partially competed for the bindings sites, indicating that they may be metabolized prior to their action as an active chemopreventive agent.