Mechanisms for premenstrual exacerbation of asthama

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Sixteen female virgin Brown Norway Rats were sensitized with ovalubumin in combination with Aluminium hydroxide injected subcutaneously and Bordetera Pertussis vaccine intraperitoneally. After sensitization was performed, female rats were ovariectomized and divided into four groups (n=4 each) as described previously. The first group consisted of ovariectomized rats which received estradiol at 3,4,7 and 8 days after ovariectomy, and progesterone at 4 and 8 days cyclically (mean basic cycle length is 4.1 day) after ovariectomy. The second group was treated only with estradiol at 3,4,7 and 8 days, the third group was treated only with progesterone at 4 and 8 days, while the fourth group received no steroid treatment. At 8 days, estradiol and progesterone treatment was done at 4 hours before the start of the antigen challenge. Eight days after ovariectomy, all groups were challenged with aerozolized ovalubumin and intra-airway pressures were monitored under mechanical ventilation to detect immediate and late airway responses followed by antigen exposure. Broncho-alveolar lavage (BAL) and histological examination were performed to evaluate the airway inflammation associated with antigen exposure eight hours after challenge. In the group received cyclical replacement of estrogen and progesterone, the magnitude of both immediate and late airway responses was significantly lowered compared to the other groups, and the number of neutrophils recovered in the BAL fluid eitht hours after challenge was significantly lowered compared to other groups. We conclude that cyclical administration of progesterone and estrogen inhibits the early-and late- phase responses to inhaled allergen in female sensitized Brown Norway Rat.