Contrasting effects of estradiol and 17β-aminoestrogens on blood clotting time in rats and mice

Estrogens have been associated with thromboembolic events. Our group has described the anticoagulant effect of 17β-aminoestrogens in rodents, potentially new alternative estrogenic agents without thrombogenic risk. This work compares the contrasting effects of estradiol and the 17β-aminoestrogens (prolame, butolame, and pentolame) on blood clotting time. Ovariectomized CD1 mice received a single injection of 17β-aminoestrogens, estradiol (20 to 80 mg/kg), or vehicle. Estradiol decreased blood clotting time from −10% to −25% (48 h; P<0.01) and 17β-aminoestrogens increased it, differing in latency (∼12 h; +48%, P<0.01) and duration (∼72 h +58%, P<0.01). In male Wistar rats, similar effects (pentolame +45%; estradiol −31%; P<0.01) were observed 48 h after five consecutive daily injections of 1000 μg/animal/day. The maximum procoagulant effect of estradiol was obtained after 72 h with 10 μg/animal/day (−45%; P<0.01). 17β-Aminoestrogens always produced opposite effects to those of estradiol on blood coagulation.