Effects of dexamethasone on the epiplexus cells in postnatal rats

The epiplexus cells in postnatal rats were markedly reduced in number and immunoreactivity for OX-42, OX-18 and ED1 following subcutaneous injections of dexamethasone. This was especially evident in rats receiving two or three successive injections of dexamethasone and killed at the age of 4 or 7 days. At 14 and 21 days, the cells did not exhibit any striking difference from their corresponding controls in terms of cell number and immunoreactivity for the above antibodies. Occasional epiplexus cells were labelled with the antibody OX-6 in both groups of rats sacrificed at different time points. In rats receiving dexamethasone coupled with rhodamine isothiocyanate (RhIc), the epiplexus cells, though fewer in number than the corresponding controls, emitted bright fluorescence. It is concluded that the reduction of epiplexus cells following dexamethasone injections is due to the suppression of their precursor cells, i.e. monocytes. The phagocytic activity of the persisting epiplexus cells did not appear to be abolished by dexamethasone as evidenced by their uptake of RhIc. Our results suggest that the effects of dexamethasone are reversible.