5-3 -Hydroxysteroid Dehydrogenase Activity in the Adrenal Cortex of the Sodium-Restricted Pregnant Rat

3βHSD activity was studied in the adrenal cortex of rats under conditions of sodium restriction, pregnancy or both. The enzyme was shown to be active primarily in the region of the transitional zone and outer fasciculata, indicating that these areas of the adrenal cortex, as well as the zona glomerulosa, are involved when aldosterone production is stimulated. Ultrastructural studies confirmed the histochemical evidence of the involvement of the transitional zone but also provided additional information suggesting a difference in the functional capacities of the zona glomerulosa and the transitional zone. The combined stimuli of sodium restriction and pregnancy led to cellular degradation of the zona glomerulosa (2) but caused no pathological changes in the transitional zone. A suggested role for this zone is that of providing transitional or precursor cells for both the zona glomerulosa and the zona fasciculata. This might account for the fact that its physiological capacity appears to be greater than that of the zona fasciculata.