Absorption, Distribution, Metabolism, and Excretion of Insect-Metamorphosing Hormone Ecdysterone in Mice.(1)

Abstract

Absorption, distribution, metabolism, and excretion of the insect metamorphosing hormone, ecdysterone, were investigated using its ³H-labeled derivative in mice. 1) When ³H-ecdysterone was administered intraperitoneally, radioactivity in all the organs examined reached the highest level 10 minutes after the administration, and decreased rapidly thereafter. After its oral administration, the initial increase and subsequent decrease of radioactivity in the organs were slow. Accumulation of radioactivity in the liver, blood, and kindeys is much greater after intraperitoneal administration than after oral administration. These findings demonstrate that its absorption from the peritoneum is easy while that from the gastrointestinal tract is poor. 2) ³H-Ecdysterone was selectively distributed in the liver in a high concentration by either route of administration, showing it to be especially concentrated, within the liver by an active transport mechanism. 3) Examination of the subcellular distribution of ³H-ecdysterone in the liver revealed that more than 80% of the radioactivity was present in the supernatant fraction and a small amount of radioactivity in other fractions. 4) In the case of intraperitoneal injection, excretion of tritium into feces and urine was fast, while tritium was excreted slowly when given orally. 5) By either route of administration, radioactivity was found much more in feces than in urine, indicating that ³H-ecdysterone absorbed is excreted mainly from the liver into the intestine via the bile. 6) Examination of radioactive substances present in the liver by means of silica gel thinlayer chromatography revealed that ecdysterone was metabolized fairly rapidly.