Oestrogen levels in the blood, not in the uterus, determine uterine eosinophilia and oedema.

This work was aimed at testing whether oestrogen-induced changes in the uterus are responsible for uterine eosinophil migration or whether the effect is due to a direct action of oestrogen on the eosinophils themselves. Uterine eosinophil migration in response to intraluminal administration of oestradiol-17 beta into one uterine horn was measured in the injected and in the untreated contralateral horns. Uterine genomic responses (luminal epithelial and myometrial hypertrophy and nucleolar enlargement), known to depend on the local intra-uterine oestrogen level, were measured to control for the absence of hormone recirculation to the uninjected horn. The effects of intravenously administered oestradiol were also determined. Intraluminal injection of 0 X 1 ng oestradiol had no effect on either horn. With 10 ng, only the injected horn exhibited the genomic responses while eosinophilia developed to the same extent in both horns. With 100 ng, the genomic responses and eosinophilia were identical in injected and in contralateral horns. The results show that eosinophil migration depends on systemic levels of oestrogen, thus indicating that it is due to an oestrogen-induced change in a property of eosinophil leukocytes rather than a change in the uterus itself. As water imbibition showed the same pattern of responses as eosinophilia, this lends further support to the hypothesis of a role for eosinophils in oestrogen-induced uterine oedema.