title: Somatomedin C-binding and action in fibroblasts from aged and progeric subjects.
abstract: Aging is associated with diminished cell growth, which has been ascribed in part to decreased cellular responsiveness to serum mitogens. To investigate whether there is an age-related loss of responsiveness to somatomedin-C (SM-C), we studied SM-C binding and action in early passage fibroblasts from normal donors, aged 7-96 yr, and one progeric subject. SM-C stimulated [3H]thymidine incorporation 4- to 16-fold in young cells, 4- to 17-fold in aged cells, and 4- to 11-fold in progeric cells. SM-C was synergistic with 0.25% human hypopituitary serum in stimulating [3H]thymidine incorporation in all cell lines. Dose-response curves for SM-C stimulation of thymidine incorporation were not significantly altered in aged or progeric cells. Half-maximal responses occurred at 5-15 ng/ml SM-C for all cell lines. [3H]Thymidine incorporation results were supported by cell replication studies. In addition, binding of [125I] SM-C was virtually identical in all cell lines, with 50% displacement at 2-5 ng/ml SM-C. Thus, in vivo aging does not appear to be associated with either an alteration in SM-C receptors or a diminished cellular responsiveness to SM-C's mitogenic effects.
authors.forename: C A
authors.initials: CA
authors.lastname: Conover
authors.forename: L A
authors.initials: LA
authors.lastname: Dollar
authors.forename: R G
authors.initials: RG
authors.lastname: Rosenfeld
authors.forename: R L
authors.initials: RL
authors.lastname: Hintz
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D002352:Carrier Proteins / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002648:Child; D004247:DNA / Q000096:biosynthesis; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007018:Hypopituitarism / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D008875:Middle Aged; D011371:Progeria / Q000378:metabolism*; D013002:Somatomedins / Q000378:metabolism* / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D004247:DNA; D013936:Thymidine