The development of ACTH-like substance during tadpole metamorphosis

Abstract

The interrenals of tadpoles of Rana catesbeiana at various developmental TK stages were frozen, sectioned, and prepared histochemically for assessment of Δ 5-3β-hydroxysteroid dehydrogenase (Δ 5-3β-HSD) activity. The interrenals of hypophysectomized (HX) tadpoles from the same batch of eggs as control tadpoles were prepared similarly for Δ 5-3β-HSD activity following a series of intraperitoneal injections of different concentrations of mammalian ACTH. The histochemically stained sections of control and HX tadpoles were scanned with a computerized microscope spectrophotometer for diformazan absorbance. Two regression equations were obtained: Y = 0.1460 + 0.0015 X and Y′ = 0.1494 + 0.0893 X′, where Y or Y′ = Δ 5-3β-HSD activity absorbance (for the control and HX tadpoles, respectively), X = developmental stages of control, and X′ = exogenous ACTH dosage administered to the HX tadpoles. Taking absorbance of Δ 5-3β-HSD activity as the common factor, a curve of concentrations of ACTH-like substance against TK stages was made. The developing concentration of ACTH-like substance was very low at first and then rose during metamorphic climax. The trend of the development of ACTH-like substance was discussed from the view point of thyroid and Δ 5-3β-HSD activities.