Anti-oestrogen modification of uterine responses to oestrogen in the rat.

Oestradiol (single injection) resulted in a peak in uterine blood flow 3 h later with a secondary rise in blood flow at 30 h. Uterine wet and dry weights increased more slowly and were still above control values 24 h after the injection. If a second injection of oestradiol was given 24 h after the first then uterine blood flow was again maximal at 3 h but remained at this level for a further 3 h, probably due to the secondary rise induced by the first injection. Uterine wet weight was further increased by the second injection of oestradiol but the effect did not occur until 6 h after the oestrogen treatment. Pretreatment with an anti-oestrogen, tamoxifen or nafoxidine, inhibited or reduced significantly the uterine weight and uterine blood flow responses to oestrogen but increased uterine weights and produced some increase in uterine blood flow when given alone. It is suggested that both blood flow and weight responses to oestrogen in the uterus are mediated through the oestrogen receptors.