title: Nature of the erythropoietin-independent response of CFU-S to steroids.
abstract: Testosterone given in vivo or in vitro triggers the pluripotent stem cell of bone marrow (CFU-S) into S-phase of the cell cycle. This action of testosterone raises many questions with regard to the cellular mechanisms utilized by testosterone for its cell-cycle effect. The extent to which triggering is coupled to the androgenic activity of this steroid or to the presence of erythropoietin is also of importance. In vitro studies in a system free of serum or plasma, steroid structure activity studies, use of the Tfm mutant system and the application of a unique steroid (batrachotoxin) and one of its antagonists (tetrodotoxin) to the CFU-S system have served to answer some of these questions. Results suggest that the cell cycle action of many steroids is erythropoietin independent, does not utilize androgen binding receptors, and does not utilize cyclase systems. Studies with batrachotoxin suggest that steroids may trigger CFU-S into S-phase by an effect upon ion conductance mechanisms at the level of the cell membrane.
mesh_terms: D000818:Animals; D001496:Batrachotoxins / Q000494:pharmacology; D003114:Colony-Forming Units Assay; D004920:Erythropoiesis / Q000187:drug effects; D004921:Erythropoietin / Q000378:metabolism*; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D013154:Spleen / Q000166:cytology; D013739:Testosterone / Q000494:pharmacology
chemical_list: D001496:Batrachotoxins; D004921:Erythropoietin; D013739:Testosterone