Functional glucocorticoid receptors in the mesonephros of the ovine fetus

Background. At 27 days of gestation in the ovine fetus (term = 145 to 150 d ays), the only kidney is the mesonephros. and allantoic fluid represents fe tal urine. The hypothesis tested in this study was that functional glucocor ticoid receptors (GRs) are present in this early mesonephric kidney. Methods. Pregnant ewes. between 26 and 30 days, were infused with saline, d examethasone (0.48 mg/hour), cortisol (5 mg/hour), or aldosterone (10 mug/h our) for 48 hours and were then killed for collection of fetuses and fetal fluids. GR mRNA was measured by real-time polymerase chain reaction in whol e fetuses, and the location of gene expression was determined by hybridizat ion histochemistry, Results. Significant changes in allantoic fluid composition were produced b y the exposure of the fetus to maternally infused synthetic (dexamethasone) and natural (cortisol) glucocorticoids, over a period of two days, compare d with fetuses of ewes infused with vehicle (isotonic saline: N = 8) or ald osterone (N = 8). Volume of fluid was unchanged by any treatment. but both dexamethasone (N = 10) and cortisol (N = 8) caused significant (P < 0.05) d ecreases in sodium and chloride concentrations and increases in concentrati ons of potassium. urea. glucose, and fructose. GR mRNA was detected in equi valent concentrations in the whole fetuses of saline, dexamethasone. and co rtisol treatments. The GR mRNA levels were significantly decreased in the a ldosterone group. By hybridization histochemistry. GR mRNA was detected in most of the tubular cells of the mesonephros. Conclusion. These results suggest that functional GRs are present in the ea rly ovine mesonephros.