Development and Validation of a Fecal Testosterone Biomarker: RESULTS(3)

RESULTS(3)

In Peromyscus, an average of 72.8 ± 12.8% of the total radiolabeled steroid was recovered from each animal. The testosterone excreted into urine and feces was very consistent between the three animals injected. Of the 73% recovered, 91.8 ± 1.5% was excreted in the first 24 h (Fig. 1). The rate vs. time profile showed two elimination phases. The first phase (a phase) occurred between 10 and 30 h after dosing and had a first-order apparent t1/2 of 2.8 h. The second phase (p) occurred between 30 and 192 h after dosing and had a first-order apparent t1/2 of 89.4 h. Urinary excretion kinetics showed three elimination phases. The alpha, beta, and gamma elimination phases occurred between 2 and 30 h, 30 and 72 h, and 72 and 192 h with t1/2 of 2.3 h, 10.6 h, and 334 h, respectively. flovent inhaler

In Mus, an average of 83 ± 15% of the total radiolabeled steroid was recovered from each animal. Of this recoverable fraction, testosterone excretion in urine and feces proved similar to values for Peromyscus, with 95.5 ± 2.0% being excreted in the first 25 h (Fig. 2). There were two elimination phases in feces. The alpha and beta elimination phases occurred between 10 and 30 h and between 30 and 77.5 h with t1/2 of 3.01 h and 11.5 h, respectively. There were also two urinary elimination phases. The alpha and beta elimination phases occurred between 2 and 30 h and between 30 and 77.5 h with t1/2 of 4.0 h and 32.0 h, respectively.

HPLC Separation

HPLC separation of ether extract from feces of a [14C]testosterone-injected Peromyscus produced two major and three minor nonpolar peaks. A polar peak comprising < 20% of the total dpm injected was detected in the first few minutes of the HPLC run. The [3H]testosterone tracer coeluted with another compound with a similar elution time in the HPLC run. The area of the peak composed of testosterone indicated that a small percentage of unconjugated testosterone had been excreted in the feces. Though peaks were not positively identified, some coeluted (± 1 fraction) with metabolites identified by Brooks: estriol at fractions 19-22 and androsterone at fractions 50-54.
Fig1Development and Validation
FIG. 1. Measurement of total dpm in excrement over time from Peromyscus after s.c. injection of [14C]testosterone. Radioactivity was measured in both urine and feces to determine the excretion profile shown (n = 3, mean ± SEM).

Fig2Development and Validation
FIG. 2. Measurement of total dpm in excrement over time from Mus after s.c. injection of [14C]testosterone. Radioactivity was measured in both urine and feces to determine the excretion profile shown (n = 3, mean ± SEM).

This entry was posted in Testosterone and tagged Biomarker, Mus musculus, Peromyscus maniculatus, Testosterone.