The effect of cortisol on the haematocrit values and serum electrolytes of the adult and foetal rat.

1. The serum sodium, potassium and chloride levels of the non-pregnant rat, pregnant rat and foetus were estimated under normal circumstances and following the administration of 3 mg/kg cortisol to the non-pregnant and pregnant rat.2. Normally, the electrolytes and haematocrit value of the non-pregnant rat and the electrolytes of the foetus were higher than those occurring in the pregnant rat.3. After treatment with cortisol, the sodium, potassium and chloride content of the serum, and the haematocrit value of the non-pregnant rat dropped significantly. There was no change in these values in the pregnant animals, but the foetus showed a significant decrease in sodium, potassium and chloride levels after maternal treatment.