NASAL MUCUS CLEARANCE IN RATS - DIFFERENCES WITH SEX AND PHASE OF THEESTROUS-CYCLE

We studied the changes in airway mucus theology and clearability, as w ell as in morphometric indices, between male rats and females in eithe r the oestrous or dioestrous phases of the oestrous cycle. Three-month -old Wistar rats were studied and the phases of the oestrous cycle wer e determined based on analysis of vaginal smears stained by a modified Shorr's procedure. Nasal mucus samples were analysed by means of magn etic rheometry and determination of in vitro transport rate in the fro g palate preparation. In situ clearance on the exposed nasal septum wa s also determined. The mucociliary velocity in situ was significantly affected by both sex and the oestrous cycle phase. In female rats, dio estrous phase clearance was significantly slower than the oestrous pha se one. Clearance in male rats was faster than that of both the phases studied in females. Mucus rigidity of females in the oestrous phase w as more rigid than that of females in the dioestrous phase and that of males. Mucus viscosity/elasticity ratio for deformations performed at high frequencies was greater for females in comparison with males. Co ugh clearability computed on the basis of theological parameters was p redicted to be more favourable in females. There were no significant d ifferences between the three groups in mucociliary clearance in vitro. Morphometric studies of the nasal epithelium showed that epithelial a nd glandular volumes did not exhibit sex- or oestrous-phase-related di fferences, but the amount of epithelial acidic glycoproteins was lower in females in the oestrous phase in comparison with males and those i n the dioestrous phase, the same trend being observed in the glands of the lamina propria, The finding of significant differences of mucus t heology and mucus airway histochemistry may be important in explaining differences between sexes in the susceptibility to the effects of air borne noxious stimulants, as suggested by some epidemiological data.