Growth factor-induced modulation of endothelin-1 binding to human smooth-muscle cells.
Endothelin-1 (ET-1) has been shown to cooperate with other growth factors to enhance mitogenesis of fibroblasts and vascular smooth-muscle cells (SMCs) in vitro. One possible mechanism underlying such enhancement is the comodulation of receptor density/affinity for one factor by the other. In previous work, we showed that pretreatment of Swiss 3T3 fibroblasts with such growth factors as epidermal growth factor (EGF), platelet-derived growth factor (PDGF), or basic fibroblast growth factor (bFGF) resulted in increased binding of 125I-ET-1 to these cells by two-, four-, and fivefold, respectively. To determine whether similar effects occur in human cells, 125I-ET-1 binding to early-passage human aortic SMCs was examined in untreated cells and in cells pretreated for 16 h with 1.0 nM of EGF, PDGF, or bFGF. In untreated cells, Scatchard analysis confirmed 26,500 +/- 2,000 (n = 4) binding sites with an apparent Kd of 105 +/- 53 pM. Pretreatment with EGF increased the number of binding sites to 36,500 +/- 4,950 (n = 3) with no significant change in Kd (128 +/- 38 pM). Similarly, pretreatment with 1.0 nM bFGF also increased the number of 125I-ET-1 binding sites to 34,000 +/- 1,700 (n = 3) with no significant change in Kd (94 +/- 13 pM). Unlike EGF and bFGF, pretreatment with PDGF-BB resulted in a decrease of 125I-ET-1 binding sites (14,600 +/- 2,300 sites/cell; n = 3) with no significant change in Kd (95 +/- 23 pM).(ABSTRACT TRUNCATED AT 250 WORDS)
Bonin
P D
PD
Cardiovascular Diseases Research, Upjohn Laboratories, Kalamazoo, MI 49001.
Leadley
R J
RJ
Erickson
L A
LA
D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D016232:Endothelins / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006133:Growth Substances / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D017466:Receptors, Endothelin / Q000187:drug effects
D016232:Endothelins; D006133:Growth Substances; D010982:Platelet-Derived Growth Factor; D017466:Receptors, Endothelin; D016222:Fibroblast Growth Factor 2; D004815:Epidermal Growth Factor