title: Effect of vitamin A acid on cyclic nucleotides of cultured keratinocytes.
abstract: Primary cultures of guinea pig ear keratinocytes were treated with vitamin A acid at plating, or at 14 h or 14 days after plating. The intracellular content of the cyclic nucleotides cAMP and cGMP was determined by radioimmunoassay at intervals during a period of 50 h after treatment. When added at plating, vitamin A acid produced a wave of DNA synthesis and increase in DNA which was at maximum between 30 and 40 h after plating, and coincided with decreased cAMP levels. This may represent a subpopulation of keratinocytes in S phase. Treatment with vitamin A acid at 14 h or 14 days after plating resulted in an immediate but temporary fall in cAMP and cGMP, and a wave of thymidine uptake but no increase in DNA per dish. Thus, a single treatment with vitamin A acid is mitogenic only when applied at plating. At other times, it can cause changes in cyclic nucleotide content without any observable cell proliferation.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism*; D000078404:Epidermal Cells; D004817:Epidermis / Q000187:drug effects*; D006168:Guinea Pigs; D013936:Thymidine / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D014212:Tretinoin; D000242:Cyclic AMP; D006152:Cyclic GMP; D013936:Thymidine