Lipid and enzyme histochemistry in differentiation of the fetal adrenal cortex in the rat

The development and differentiation of the fetal adrenal cortex was studied in the rat by lipid and enzyme histochemistry.The adrenal cortex began to have small amounts of lipid droplets at 171/2 days by oil red O stain and the amounts increased gradually. Cholesterol by Schultz reaction became clear at 201/2 days. At 151/2 days weak activity of glucose 6-phosphate dehydrogenase (G-6-PDH) was already present in the inner cortex, which was followed a day later by weakly positive reaction of 3β-hydroxysteroid dehydrogenase (3β-HSD). At 181/2 days positive activity of secondary alcohol dehydrogenase (SAD) was obvious in the inner cortex. Activity of alkaline phosphatase (Al-Pase) was observed in the subcapsular zone from day 181/2 on. Enzymatic activities of the cortex increased gradually after their appearance as development proceeded. These findings show that histochemical activities of such principal enzymes as G-6-PDH and 3β-HSD precede appearance of lipid droplets.As a conclusion, zona reticularis is not distinguishable from zona fasciculata during the fetal stage, zona fasciculo-reticularis differentiates histochemically in a 171/2 day old fetus, and finally differentiation of zona glomerulosa occurs at 201/2 days in gestation.