MITOGENIC ACTIONS OF ENDOTHELIN AND OTHER GROWTH-FACTORS IN-OVINE ENDOMETRIUM

Endothelin-l (ET-1) is present in ovine endometrium, primarily in epit helial cells, and increases around the time of implantation. We examin ed the cell. type expressing ET-binding sites in vitro and whether ET- 1 has mitogenic actions in the endometrium, alone or in synergy with o ther growth factors. Purified epithelial and stromal cells were prepar ed from luteal-phase endometrium. Specific receptors were demonstrated by binding of I-125-ET-1 and proliferative effects of ET-1 and/or oth er growth factors determined by uptake of [H-3] thymidine by cells in serum free culture. I-125-ET-1 bound to both epithelial (2516+/-820 c. p.m./well) and stromal (6368+/-1350 c.p.m./well) cells and was displac ed by ET-1 (1 mu mol l(-1)) There were no proliferative effects of ET on epithelial cells. ET-1 (10 nmol 1(-1)) stimulated uptake of [H-3]th ymidine by stromal cells under serum-free conditions in 13/20 individu al cell preparations, to 149+/-13% of control (untreated=100%) with do se-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 prolife ration 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 1(-1); 110+/-2, 3/3). AU stimulations except that of EGF were significant and dose-responsi ve but only insulin was additive with ET (350+/-35, 5/5). ET-1 also st imulated expression of the the AP-1 cis element c-jun, this being maxi mal at 60 min oi exposure to mitogen. ET-1, along with other growth fa ctors has a likely paracrine role in cellular proliferation in the end ometrium, possibly in association with blastocyst implantation.