The Use of Polyethylene Estrogen Capsules in the Chronic Steroid Treatment of Prepubertal Female Rats

Abstract
A polyethylene capsule suitable for the administration of small amounts of E2 [17 .beta.-estradiol] to young ovariectomized rats is described. A 2.5-mm polyethylene capsule diluted 1:1 with cholesterol produced a uterine weight and incidence of vaginal opening comparable to that in the intact animal. Under in vitro conditions, this capsule released 0.78 ng E2/hr, while Silastic capsules of comparable size, containing 100% E2, produced 100 ng E2/hr.