Plasma Kinetics, Excretion in Milk and Tissue Levels in the Cow following Implantation of Trenbolone Acetate®

Abstract

The plasma kinetics of biologically stable tritiated trenbolone acetate have been studied in the barren, dry and in the lactating dairy cow following a single intravenous injection and implantation. The excretion of the compound in milk has been investigated. Tissue levels were measured 3 or 5 months following implantation. The ester function is hydrolysed rapidly to yield the alcohol derivative which very early on constitutes the main radioactive fraction. The metabolites have high clearance rates: the total radioactivity ratio between .1 and 24 hr after injection is 100. The resorption of implants is slow and the low tissue concentrations at slaughter are due to their residual presence. These concentrations, in general approximating 1 ppb, except in the case of the liver and kidney, i.e., the organs of excretion and metabolism, are mainly due to polar compound. Perirenal fat is the only tissue where some unmetabolized compound could be found. Radioactivity is excreted via the bile and urine. Copyright © 1975. American Society of Animal Science. Copyright 1975 by American Society of Animal Science.