ENHANCED RESPONSE TO OZONE EXPOSURE DURING THE FOLLICULAR PHASE OF THE MENSTRUAL-CYCLE

Exposure to ozone (03), a toxic component of photochemical smog, resul ts in significant airway inflammation, respiratory discomfort, and pul monary function impairment. These effects can be reduced via pretreatm ent with anti-inflammatory agents. Progesterone, a gonadal steroid, is known to reduce general inflammation in the uterine endometrium. Howe ver, it is not known whether fluctuations in blood levels of progester one, which are experienced during the normal female menstrual cycle, c ould alter 03 inflammatory-induced pulmonary responses. In this study, we tested the hypothesis that young, adult females are more responsiv e to O3 inhalation with respect to pulmonary function impairment durin g their follicular (F) menstrual phase when progesterone levels are lo west than during their mid-luteal (ML) phase when progesterone levels are highest. Nine subjects with normal ovarian function were exposed i n random order for 1 hr each to filtered air and to 0.30 ppm O3 in the ir F and ML menstrual phases. Ozone responsiveness was measured by per cent change in pulmonary function from pre- to postexposure. Significa nt gas concentration effects (filtered air versus 03) were observed fo r forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1 ), and forced expiratory flow between 25 and 75% of FVC (FEF25-75; p<. 05). More importantly, the pulmonary function flow rates, FEV1 and FEF 25-75, showed a significant menstrual phase and gas concentration inte raction effect, with larger decrements observed in the F menstrual pha se when progesterone concentrations were significantly lower. We concl ude that young, adult females appear to be more responsive to acute O3 exposure during the F phase than during the ML phase of their menstru al cycles. This difference in pulmonary function response could be rel ated to the anti-inflammatory effects of increased progesterone concen trations during the luteal phase.