Hormonal regulation of development of the interrenal activity of Δ5‐3β‐hydroxysteroid dehydrogenase in bullfrog tadpoles

Since interrenal activity of Δ5‐3β‐hydroxysteroid dehydrogenase (Δ5‐3β‐HSD) in tadpoles during development follows the pattern of metamorphic progress (Hsu et al., '80) and Δ5‐3β‐HSD is a key enzyme in biosynthesis of corticosteroids, hypophysectomized (HX) tadpoles of Rana catesbeiana were injected with thyroxine (T4) or ACTH or T4 + ACTH. The untreated HX tadpoles served as controls. Interrenals of the four groups of tadpoles were prepared histochemically for assay of Δ5‐3β‐HSD activity. The reaction products in terms of absorbance were scanned under a defined area with a computerized microscope spectrophotometer. The results show that T4 or ACTH alone or T4 + ACTH together raised the enzyme activity above that of the controls significantly. The findings suggest an endogenous role of T4 and ACTH in development of this enzyme activity in tadpole interrenals.