title: beta-Adrenergic receptors and cyclic AMP responses to epinephrine in cultured human fibroblasts at various population densities.
abstract: The beta-adrenergic receptors of the intact human lung diploid fibroblast line Wl-38 and an SV-40 transformed clone of Wl-38, Wl-38-VA-13-2RA (VA13), were estimated in experiments utilizing the beta-adrenergic ligand, 125l-hydroxybenzylpindolol (125IHYP). When specific 125IHYP binding was measured in cells grown to relatively low population densities (0.15x10(6)cells/35mm dish), both Wl-38 and VA13 cells had approximately 40,000 beta-adrenergic receptors per cell. Wl-38 cells, when cultured to a high population density (0.5x10(6) cells/35/mm dish) had clearly diminished numbers of beta-adrenergic receptors and greatly decreased cAMP responses to epinephrine stimulation. On the other hand, in VA13 cells, neither the receptor number nor the beta-adrenergic response was affected by cell population density. In Wl-38 cells, the diminished cAMP response to epinephrine paralleled the decrease in number of beta-adrenergic receptors. Prostaglandin E1 (PGE1) stimulation of cAMP levels was unaffected by cell population density in either Wl-38 or VA13 cells. Thus, increased cell population density, perhaps related to density dependent inhibition of growth, caused a specific diminution in 125IHYP binding concomitant with decreased cAMP responses to epinephrine.
mesh_terms: D002452:Cell Count; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism*; D004837:Epinephrine / Q000494:pharmacology*; D005347:Fibroblasts / Q000502:physiology; D006801:Humans; D007700:Kinetics; D008168:Lung; D010646:Phentolamine / Q000494:pharmacology; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*
chemical_list: D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; C011878:iodohydroxybenzylpindolol; D010869:Pindolol; D000242:Cyclic AMP; D004837:Epinephrine; D010646:Phentolamine