Progesterone interaction with eosinophils and with responses already induced by oestrogen in the uterus.

Progesterone pretreatment decreases oestrogen-induced uterine eosinophilia and other non-genomic responses that are possibly mediated by eosinophils. To investigate the mechanisms of this interaction, the present study describes the effects of progesterone on oestrogenic responses already induced by oestrogen treatment and the in-vivo and in-vitro effects of progesterone on blood eosinophils. Progesterone treatment of oestrogen-pretreated animals potentiated uterine eosinophilia 24 h after progesterone treatment but decreased it at later times and increased eosinophil degranulation in vivo. In addition, progesterone degranulated blood eosinophils in vitro. These findings demonstrate interaction of progesterone with oestrogenic responses mediated by eosinophils. Progesterone interaction with other oestrogenic responses was analysed for comparison; evidence is shown suggesting a role of eosinophils in oestrogen-induced uterine luminal fluid accumulation.