Vascular,Metabolic,and Motility Responses of Uterine Tissue Following Administration of Oestrin

Within 30 minutes after the administration of oestrin to ovariectomized rabbits, a maximal hyperemia of the uterine vascular bed takes place. 1 , 2 , 3 , 4 Rhythmic motility of the myometrium does not commence until about the tenth hour after injection of oestrin, and increases progressively until about the twenty-fourth hour. 5 , 6 , 2 In addition to these two effects, oestrin also raises the metabolic rate of uterine tissue. 7 , 8 , ⁹, ¹⁰ The present experiments were performed to ascertain to what extent the initial hyperemia, rise of metabolic activity of the tissue and motility are related to each other.

Two main groups of experiments were performed. In one, the O₂ consumption rate was measured in a group of untreated rabbits (3½ to 4 months of age), 5 of which were intact and the remainder of which (21 animals) were ovariectomized for periods ranging from 2 to 15 days. In the second group, the O₂ consumption rates were measured at intervals of 5, 10, 18, and 24 hours after a single intramuscular injection of 500 international units of oestradiol to rabbits ovariectomized for 9 to 11 days. The tissues were taken immediately after cerebral concussion. Each uterine horn was slit longitudinally throughout its length. Three segments were taken from each uterus, a tubal and a cervical piece from one horn and a section from the middle of the opposite horn, Oxygen consumption measurements were made in Fenn respirometers at a temperature of 37.5°C. After a 15-minute period of equilibration the chambers were closed and readings were made at 10-minute intervals throughout an hour. The hourly consumption of oxygen per milligram of dried tissue (QO₂) was determined for the various pieces of tissue dried to constant weight at 85°C.