Two male calves, each given s.c. implantations with 140 mg TBA at
the base of the right ear, showed a high urinary elimination rate of
trenbolone (TBOH) (detected fluorometrically). Within 3 hours after
application relatively high concentrations were measured (50-80 ng/mg
creatinine); the maximum TBOH level was reached after 10 hours (about
120 ng/mg creatinine) followed by a sudden drop within two days.
Additional implantation of estradiol-17ß reduced TBOH excretion very
slightly (Bouffault, 1977).
Groups of 3 - 4 bull calves were given s.c. implantations of
20 mg 3H-estradiol-17ß or 20 mg 3H-estradiol-17ß + 140 mg TBOH.
TBOH caused a marked delay in estradiol excretion. In calves receiving
estradiol only, the maximum plasma estradiol-17ß level was 3 nmole/l,
and 95% of the applied radioactivity was excreted in the urine and
faeces within 20 days; after more than 31 days radioactivity was no
longer detectable in the urine or faeces. Calves treated with TBOH
showed a maximum plasma estradiol-17ß level of 0.33 nmole/l and
excretion of radioactivity was observed up to 107 days after
administration; at that time faecal and urinary radioactivity levels
were still 1.4 - 3 nCi/g (Riis & Suresh, 1976).
Twelve calves weighing 150 - 200 kg each received s.c. implants
in the ear containing 200 mg 3H-TBA. Half of the animals were
sacrificed at 15 days, the other half at 30 days after implantation.
Blood samples were taken at intervals between dosing and sacrifice. At
sacrifice, the liver, kidneys, and samples of muscle, fat, and bile
were taken for analysis. Concentrations of radioactivity in the plasma
were fairly constant during the experimental period, with mean levels
of 4 to 5 ng equivalents/ml. Tissue concentrations of radioactivity
were either similar at 15 and 30 days or were higher at 30 days.
Highest concentrations were found in the liver (42 and 49 ng
equivalents/g at 15 and 30 days, respectively). Lower concentrations
were found in the kidneys (15 - 20 ng equivalents/g) and muscle and
fat (2 - 3 ng equivalents/g). High concentrations of radioactivity in
the bile (1073 and 736 ng equivalents/ml at 15 and 30 days,
respectively) indicate its importance in excretion of this compound.
Comparison of total and non-volatile radioactivity showed that only a
small amount of tritiated water was produced. About 10% of the
radioactivity in the liver samples was extracted by diethyl ether or
ethyl acetate, and this proportion increased to about 20 - 30%
following incubation with ß-glucuronidase, indicating the presence of
a glucuronide(s) (Hawkins et al., 1984).
Two heifers were given single s.c. implantations with 300 mg
3H-labelled TBA. One heifer was killed 60 days after implantation;
the implant was removed from the other heifer after 60 days and the
animal was killed 16 days later. The H content in the liver, kidneys,
muscle, and fat varied from 0.5 to 25 ppb. Of these residues, 1 - 5%
was TBA, TBOH, and trenbolone glucuronide; up to 5% was found in other
organic-soluble material. Of the remaining radioactivity, about 50%
was water soluble, and the insoluble residue could be made water
soluble by treatment with the proteolytic enzymes pepsin and trypsin
(Ryan & Hoffman, 1978).
Two heifers were given single s.c. implantations with 300 mg
3H-labelled TBA. After 60 days the implants, which still contained
31% of the initial radioactivity, were removed. One heifer was killed
immediately, the other was maintained for 16 days after implant
removal and then killed. Ethyl acetate-extractable radioactivity in
blood plasma could largely be ascribed to TBOH; in most cases no TBA
was found in plasma. Plasma concentrations during days 1 - 55 after
dosing were 5 - 13 ppb; after 58 days a large increase in both total
and nonvolatile radioactivity was observed (17 - 20 ppb). The
half-lives for plasma disappearance of total and non-volatile
radioactivity were 32 and 29 days, respectively, during the
implantation period and 18 and 14 days, respectively, during the
withdrawal period. Plasma ethyl acetate-extractable radioactivity
amounted to 10 - 74% of the total radioactivity during days 1 - 55
after implantation, and this declined to 5% at 16 days after implant
removal. In the 16 days from implant removal to sacrifice,
radioactivity decreased by 58% in muscle, 75% in liver, 77% in
kidneys, and 74% in fat (Chasseaud et al., 1976).
Heifers (aged 15 months, number not given) were given daily oral
doses of 0.4 or 8 mg TBA per animal for 9 weeks. After 1 and 2 weeks
TBA was detected in the urine. Two weeks after drug withdrawal the
compound was detected in some urine samples, whereas after 3 weeks no
TBA was detected (Stephany et al., 1976).
A 14-month-old heifer, after i.v. administration of 10 mg/kg b.w.
TBA, excreted 80% of the administered radioactivity in the bile during
the first 24 hours; 3.5% was in the free form, 30% was excreted as
glucuronides, and 30% as sulfates. Metabolites with the 3-ketotrienic
structure that were identified in the bile are presented in Figure 2.
Three compounds that had lost their ketotrienic structure were also
isolated; these metabolites are presented in Figure 3. Less than 1% of
the administered radioactivity was isolated as tritiated water
(Pottier et al., 1978).
Specimens of muscle from the back and rear leg and specimens from
the liver were taken from two heifers that had been implanted two
months earlier with 300 mg 3H-TBA. In addition, bile was collected
by catheterization of one heifer on days preceding slaughter. The
radioactivity content of muscle, independent of its location, was
one-tenth the level in liver, whereas radioactivity levels in the bile
were 15 times higher than in liver tissue, alpha-TBOH and ß-TBOH
concentrations were determined by reverse isotopic dilution. On
average, the concentration of ß-TBOH was 0.05 to 0.1 ppb in various
tissues, whereas that of alpha-TBOH, which was only 0.005 ppb in the
muscle, reached 0.88 ppb in the liver. Following enzymolysis, ß-TBOH
was not detected in the bile, which contained, by contrast, nearly
200 ppb alpha-TBOH. Thus, alpha-TBOH represented 10% of total TBOH in
muscle, 90 - 95% in the liver, and more than 99% of the total in bile
(Pottier, 1979).
3H-TBA was implanted in the ears of two heifers (300 mg;
388 mCi) and the distribution of the radioactivity in liver and muscle
tissue was determined, applying rigorously standardized organic or
aqueous extraction procedures, either directly or following enzymatic
hydrolysis and proteolytic procedures. These steps yielded almost 100%
recovery of the radioactivity and indicate that only 5 to 15% of the
total residues were extractable with organic solvents. The remaining
radioactivity was either soluble in aqueous media or remained bound to
tissue structures. In another experiment, liver tissue from a calf
treated with 3500 mg TBA 68 days prior to slaughter was examined by
applying radioimmunoassay techniques to determine TBA/TBOH ratios.
Trienic-steroid type residues were obtained only from fractions
containing residues extractable with organic solvents (Hoffman et al.,
1984).
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