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PubMed1982

Peripheral testosterone in boars after administration of hCG, ACTH and testosterone at three ages.

Forty-four purebred Yorkshire boars, reared outdoors on concrete, were randomly assigned to one of three age groups (150 +/- 7, 200 +/- or 250 +/- 7 days of age) for the purpose of examining endogenous testosterone concentration in response to one of four exogenously administered treatments. Four boars from each age group were administered either human chorionic gonadotrophin (hCG; 1000 U.S.P. units intravenous), adrenocorticotrophin (ACTH; 100 IU intravenous), or testosterone proprionate (TP; 25 mg intramuscular). The remaining boars served as controls and were given saline (S; 5 ml IV). Blood samples were collected from each boar at -120, -90, -60, -30, and 0 min pre-treatment and at 15, 30, 45, 60, 75, 90, 105, 120, 150, 180, 210, 240, 270, 300, 330, and 360 min post-treatment via an indwelling anterior vena cava catheter. Plasma testosterone was quantified by radioimmunoassay. Within treatment, boars receiving hCG, ACTH or S responded similarly (P>.10) across the three age groups for measured testosterone. Plasma testosterone was elevated (P<.05) by 30 min (4.7 +/- .5 ng/ml; X +/- SEM) and 15 min (5.5 +/- 1.1 ng/ml) post-treatment in boars administered hCG and ACTH, respectively, when compared with the S (1.0 +/- .3 ng/ml) group. Testosterone in hCG treated boars peaked by 90 min (21.8 +/- 1.8 ng/ml) post-treatment, declined slightly until 210 min (18.8 +/- 1.8 ng/ml) post-treatment and increased thereafter. Hormone levels in ACTH treated boars plateaued by 45 min (7.5 +/- 1.4 ng/ml) post-treatment and began to decline by 90 min post-treatment. Plasma testosterone for TP treated boars differed (P<.05) over time among the three age groups. Boars 150 +/- 7 and 200 +/- 7 days of age had an increase in plasma testosterone at 150 and 240 min post-treatment with TP, respectively. Results suggest that the testosterone biosynthetic and secretory capabilities of the boar testes are fully operational by 150 days of age.

Journal Article↗
PubMed2003

Testosterone undecanoate: a useful tool for testosterone administration in rats.

A major obstacle of testosterone (T) treatment in experimental animals is the difficulty of maintaining long-term physiologic/anabolic steady serum levels after exogenous T administration. In two complementary studies we investigated the pharmacokinetic properties of different T formulations in male rats. Study I. Mature male Wistar rats (> 380 g, n = 4 - 7/group) were divided into four treatment groups: (1) sham-operated non orchiectomised (non-ORX) and placebo; (2) orchiectomised (ORX) and subcutaneous testosterone pellets (TP) (15, 25, 75 mg/60 days release or placebo pellets); (3) ORX and a single injection of testosterone undecanoate (TUD) (31, 62.5 or 125 mg/kg body weight subcutaneously (s.c.) or vehicle; (4) ORX and testosterone propionate (Tprop) (10, 20, 40 mg/month) or vehicle as a single injection s.c. Serum T was measured at baseline and in weekly intervals for 4 weeks. Study II. Mature male Wistar rats (180 - 200 g) were randomly assigned to one of 5 experimental groups (n = 5 - 6/group): (1) normal untreated rats (controls); (2) ORX untreated rats, and non-ORX rats receiving one of three treatment options; (3) 250 mg/kg body weight TUD i.m. (TUD 250); (4) 500 mg/kg body weight TUD i.m. (TUD 500); (5) 100-mg testosterone pellet/90 days release s.c. (TP 100). Serum T was measured at baseline and in intervals for 6 weeks after T administration. In both studies, the kinetic profile of TUD showed favourable continuous steady state levels over several weeks. In contrast, testosterone release by subcutaneous pellets resulted in a shorter than expected duration of elevated serum T levels with high inter-individual variability. Tprop administration led to only a short-lasting serum T increase with low serum T levels already 14 days after injection. In conclusion, a single injection of TUD (100 mg/kg body weight s.c.) is effective in inducing physiological testosterone levels in ORX rats for a minimum of four weeks. High dose TUD (500 mg/kg body weight i.m.) given as a single injection results in supraphysiological anabolic testosterone concentrations for up to six weeks in non-ORX rats. TUD was superior to other T release preparations and represents a convenient and effective tool for T administration in experimental animals.

Anabolic Agents↗
PubMed1999

Electrospray collision-induced dissociation of testosterone and testosterone hydroxy analogs.

Complications with the gas chromatographic analysis of steroids prompted the use of alternative techniques for their identification. High-performance liquid chromatography/mass spectrometry with atmospheric pressure ionization allowed the collection of data for structural identification of these compounds. The objective of this study was to investigate the up-front collision-induced dissociation (UFCID) electrospray ionization (ESI) mass spectra of testosterone and monohydroxylated testosterones. The positive ion UFCID ESI mass spectrum of testosterone showed three significant ions at m/z 97, 109 and 123. The relative abundance of these ions in the UFCID ESI mass spectra of monohydroxylated testosterones varied with the position of the hydroxy group. Statistical data allowed the prediction of hydroxy group position on testosterone by evaluation of the relative abundance of the m/z 97, 109, 121 and 123 ions. Data from the ESI mass spectral analysis of testosterone in a deuterated solvent and from the analysis of cholestenone and 4-androstene-3 beta, 17 beta-diol indicated that the initial ionization of testosterone occurred at the 3-one position. CID parent ion monitoring analyses of the m/z 97, 109 and 123 ions indicated that each resulted from different fragmentation mechanisms and originated directly from the [M + H]+ parent ion. The elemental composition of these fragment ions is proposed based on evidence gathered from the CID analysis of the pseudo-molecular ions of [1,2-2H2]-, [2,2,4,6,6-2H5]-, [6,7-2H2]-, [7-2H]-, [19,19,19-2H3]- and [3,4-13C2]testosterone. The structure and a possible mechanism of formation of the m/z 109 and 123 ions is presented. The results of this study advance the understanding of the mechanisms of collision-induced fragmentation of ions.

Chromatography, High Pressure Liquid↗