Early oestrogen-induced changes in uterine albumin exchange in mice.

The effect of the oestrogens, oestradiol and oestriol, on plasma albumin dynamics in the uterus was studied in mice. A double isotope technique with 125I- and 131I-labelled human serum albumin was used. The optimum conditions to measure the extravascular accumulation of albumin were to use one labelled albumin as "permeability marker" (30 min circulation time) the other as plasma volume indicator (3 min circulation time). The oestrogens increased the extravascular accumulation of labelled albumin in the uterus but not in diaphragm or heart muscle. The accumulation was maximal after 4 h (75% higher than in controls) and was significant as early as 2 h after oestrogen administration. It cannot be decided whether the increase in labelled albumin accumulation was due to an increase in permeability and/or to an increase in the total surface area of perfused capillaries.