Mitogenic actions of endothelin and other growth factors in ovine endometrium

Abstract Endothelin-1 (ET-1) is present in ovine endometrium, primarily in epithelial cells, and increases around the time of implantation. We examined the cell type expressing ET-binding sites in vitro and whether ET-1 has mitogenic actions in the endometrium, alone or in synergy with other growth factors. Purified epithelial and stromal cells were prepared from luteal-phase endometrium. Specific receptors were demonstrated by binding of 125 I-ET-1 and proliferative effects of ET-1 and/or other growth factors determined by uptake of [ 3 H]thymidine by cells in serum-free culture. 125 I-ET-1 bound to both epithelial (2516 ± 820 c.p.m./well) and stromal (6368 ± 1350 c.p.m./well) cells and was displaced by ET-1 (1 μmol l −1 ). There were no proliferative effects of ET on epithelial cells. ET-1 (10 nmol l −1 ) stimulated uptake of [ 3 H]thymidine by stromal cells under serum-free conditions in 13/20 individual cell preparations, to 149 ± 13% of control (untreated=100%) with dose-dependence between the range of 1 to 100 nmol l −1 . Stimulation by fetal calf serum was to 377 ± 126% of control. The effects on proliferation by other growth factors (dose; % of control ± s.e.m. , number of positives/total number of cell preparations) were: IGF-I (13 nmol l −1 ; 182 ± 14, 4/4), epidermal growth factor (EGF; 4·8 nmol l −1 ; 132 ± 5%, 7/7), platelet-derived growth factor-BB (0·4 nmol l −1 ; 146 ± 3, 2/2) and leukaemia inhibitory factor (0·4 nmol l −1 ; 110 ± 2, 3/3). All stimulations except that of EGF were significant and dose-responsive but only insulin was additive with ET (350 ± 35, 5/5). ET-1 also stimulated expression of the the AP-1 cis element c-jun, this being maximal at 60 min of exposure to mitogen. ET-1, along with other growth factors has a likely paracrine role in cellular proliferation in the endometrium, possibly in association with blastocyst implantation. Journal of Endocrinology (1997) 152, 283–290