title: Activin expression by cultured human retinal pigment epithelial cells.
abstract: OBJECTIVE
  To determine whether human retinal pigment epithelial (hRPE) cells produce activin, a growth factor in the transforming growth factor beta family, and to characterize growth regulatory effects of activin on retinal pigment epithelium.
  
  
  METHODS
  mRNA expression was examined using polymerase chain reaction with primers specific for the beta A and beta B chains of activin and by slot blot analysis with a probe specific for the beta A chain. Protein localization was determined immunocytochemically using antibodies specific for the beta A chain of activin and intact activin A. The effect of activin A on DNA synthesis was studied by measuring (3H) thymidine incorporation after cells were exposed to recombinant human activin A (rhA). Growth regulatory effects of rhA on hRPE cells were examined with cell growth assays.
  
  
  RESULTS
  beta A mRNA was expressed constitutively in 8/8 cells lines tested. beta B mRNA was not expressed in any of the six cell lines tested but was expressed in human ovarian granulosa cell controls. Positive immunostaining was observed for both the beta A chain and intact activin A. (3H) thymidine incorporation was inhibited 44% (P < 0.025), 45% (P < 0.025), and 44% (P < 0.015) when RPE cells were exposed to 100 ng/ml rhA and grown in serum-free medium, medium with 0.5% serum, and 1% serum, respectively. Cell growth was inhibited 33.2% (P = 0.0001) after RPE cells were exposed to 100 ng/ml rhA for 8 days.
  
  
  CONCLUSIONS
  These results suggest that activin A can act as an autocrine-paracrine growth regulator in RPE cells and may help control cellular growth in ocular development and proliferative eye disease.
authors.affiliation: Department of Ophthalmology, Duke University, Durham, North Carolina 27710.
authors.forename: G J
authors.initials: GJ
authors.lastname: Jaffe
authors.forename: C E
authors.initials: CE
authors.lastname: Harrison
authors.forename: G M
authors.initials: GM
authors.lastname: Lui
authors.forename: W L
authors.initials: WL
authors.lastname: Roberts
authors.forename: P C
authors.initials: PC
authors.lastname: Goldsmith
authors.forename: S
authors.initials: S
authors.lastname: Mesiano
authors.forename: R B
authors.initials: RB
authors.lastname: Jaffe
mesh_terms: D028341:Activins; D002454:Cell Differentiation; D002455:Cell Division; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D006133:Growth Substances / Q000096:biosynthesis / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007265:Inhibins / Q000096:biosynthesis / Q000378:metabolism*; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism*
chemical_list: D006133:Growth Substances; D012333:RNA, Messenger; D028341:Activins; D007265:Inhibins; D004247:DNA