THE IN VIVO GLUCURONIDE CONJUGATION OF RADIOACTIVE ETIOCHOLANOLONE AND ANDROSTERONE BY THE DOG KIDNEY *

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Abstract
The conjugation of radioactive etiocholanolone and androsterone to their respective glucuronides was demonstrated (in vivo) in a dog kidney preparation. These glucuronides, isolated from the renal vein plasma, were characterized by their mo-bilities on paper electrophoresis, paper chromatography, hydrolysis with [beta]-glucuronidase, and paper chromatography of the resultant "free" compound. Significant radioactivity persisted throughout the isolation and identification procedures. In one experiment androsterone glucuronide was characterized by purification to constant specific activity. No significant amounts of radioactive glucuronide conjugates were found in the urine or internal jugular vein plasma. Highly significant amounts of free isotope were "trapped" in the kidney parenchyma. Three to 16.5% of the injected dose of the labeled steroid/100 ml of plasma was converted to the steroid glucuronide during the 6- to 8-minute perfusion of the kidney. A hypothesis is presented which may explain the higher yields of etiocholanolone glucuronide than of androsterone glucuronide formed by this technique. The lesser steric hindrance of the equatorial a -hydroxyl group on the 3d carbon atom of etiocholanolone may facilitate rapid glucuronide conjugation. Although androsterone is conjugated readily, the rate of the reaction may be slightly less because of steric hindrance of the axially placed a-hydroxyl group on the 34 carbon atom.