Androgen Metabolic Pathways Research Articles

The influence of insulin-like growth factor (IGF) on C19 steroid conversions by human gingiva and in cultured gingival fibroblasts.

The metabolic conversion of 14C-testosterone by human gingival tissue in response to IGF was studied. Androgen metabolic studies were also performed in 5 to 7 cell-lines of cultured gingival fibroblasts, using 14C-testosterone and 14C-4-androstenedione as initial substrates. Duplicate incubations of gingival tissue were performed after establishing the wet weight, in Eagle's MEM + 10% FCS and optimal stimulatory concentrations of IGF for 24 hours. Similar incubations were performed in duplicate with cell-lines of gingival fibroblasts, control/IGF, and 14C-testosterone/14C-4-androstenedione. At the end of the incubation period, the radioactive metabolites were extracted, evaporated, subjected to thin layer chromatography for their separation, and quantified by scanning in a Berthold's linear analyzer. With the gingival tissue samples, IGF caused a 4-fold increase in 5 alpha-dihydrotestosterone (DHT) synthesis (n = 5; P < 0.1, Wilcoxon signed rank test for paired observations) and a 3.5-fold increase in 4-androstenedione formation (n = 5; P < 0.1) from 14C-testosterone. When similar incubations were performed with cell-lines of fibroblasts and 14C-testosterone, average values of duplicate incubations showed a 2.5-fold increase in DHT synthesis in response to IGF (n = 7; P < 0.002) and a 2.3-fold increase in 4-androstenedione formation (n = 7; P < 0.002). With 14C-4-androstenedione as substrate, IGF stimulated a 2.7-fold increase in DHT synthesis (n = 5; P < 0.1) compared with controls and a 1.8-fold increase in testosterone formation (n = 5; P < 0.1). Since both DHT and IGF are implicated in protein turnover by fibroblasts, significant stimulation of DHT synthesis by IGF in gingiva and cultured fibroblasts is suggestive of a possible mechanism for mediating inflammatory repair via the androgen metabolic pathway.

Multivariate analysis of plasma hormones in patients with metastatic prostate cancer receiving combined LHRH‐analog and antiandrogen therapy

The following hormones, the plasma protein SHBG, and the tumor markers prostatic acid phosphatase (PAP) and prostate-specific antigen (PSA) were assayed at 18 time-points over 1 month during a double-blind randomized study in 36 stage D2 cancer patients receiving either "buserelin+placebo" or "buserelin+nilutamide (Anandron)": LH, FSH, estradiol, testosterone, dihydrotestosterone, androstenedione, 5-androstene-3,17 beta-diol, dehydroepiandrosterone and its sulfate, cortisol, 17 alpha-hydroxyprogesterone, pregnenolone, 17 alpha-hydroxypregnenolone, and 3 alpha-androstanediol glucuronide. Multivariate analysis of the treatment values (over 10,000 assays) by two complementary methods, correspondence factorial analysis (CFA) and the minimum spanning tree (MST) method, identified those variables within the pathways of androgen metabolism that were correlated over time and, in a comparison of the two treatment groups, identified the enzyme targets of nilutamide action in humans. Whereas nilutamide tended to decrease androstenedione slightly, it affected no other variables including cortisol, except for pregnenolone, 17 alpha-OH-pregnenolone, and 17 alpha-OH-progesterone, which were increased. These increases are indicative of weak inhibition of C17,20 lyase by nilutamide, but, according to the multivariate analysis, are insufficient to account for the more marked and rapid fall in PAP and PSA noted on addition of nilutamide to buserelin that must therefore be explained by another mechanism such as androgen receptor blockade by nilutamide.

Drug metabolism in Octodon degus: Low inductive effect of phenobarbital

1. Differential effects of phenobarbital pre-treatment on liver microsomal drug metabolizing enzymes were registered in Octodon degus. 2. Glucuronidation reaction for morphine was decreased but that for p-nitrophenol was significantly increased. 3. Oxidative reactions such as naphthalene hydroxylation, morphine and aminopyrine N-demethylation were modestly increased. 4. In phenobarbital treated Octodon degus, testosterone metabolic pathways were decreased, not inducible or absent. 5. Spectral studies revealed two binding sites with different affinities for aniline in Octodon degus liver microsomes. 6. The poor phenobarbital induction on drug metabolism in Octodon degus may be a result of deficiency of androgen metabolic pathways associated to drug metabolizing enzymes.

Hirsutism

Hirsutism can be defined as excessive growth of coarse, terminal body hair (in a male pattern) in a female. The evaluation of a hirsute patient takes time, interest, and knowledge of specific androgen-dependent cutaneous syndromes involving multiple possible enzymatic defects in the conversion of cholesterol to testosterone or intercellular pathways of androgen metabolism. The androgen status of a hirsute woman can be diagnosed, today by new techniques tor measuring circulating androgens. Unfortunately, a battery of expensive tests is required in order to make this assessment.

Effects of photoperiod on formation of oestradiol-17 beta in the dove brain.

The effects of photoperiod and castration on brain aromatase activity have been examined using an in-vitro radioassay. Formation of oestradiol-17 beta was lower in the preoptic area of male Barbary doves on a short daylength (6 h light:18 h darkness) than in males on a long daylength (14 h light:10 h darkness). This was a specific effect of photoperiod which did not influence aromatase activity in the anterior or posterior hypothalamic areas, and was not accompanied by changes in hormone-sensitive vocal behaviour. Production of 5 beta-dihydrotestosterone, 5 beta-androstane-3 alpha, 17 beta-diol and 5 alpha-dihydrotestosterone by the preoptic area did not differ between birds on long or short days. Therefore, a short photoperiod does not appear to influence other pathways of androgen metabolism. In contrast to the effects of photoperiod, castration reduced oestradiol formation in both preoptic and hypothalamic areas. Intramuscular injection of testosterone propionate (TP) in intact males on short days did not restore the pattern of distribution of aromatase activity seen in males on long days. Preoptic aromatase activity was, however, restored by TP in castrated birds. We conclude that a short photoperiod influences both the activity of aromatase and the inductive effect of testosterone on enzyme activity in the preoptic area, which is known to be associated with the behavioural action of oestrogen in the dove. Photoperiod is likely to act both through changes in circulating androgen and by a direct action on preoptic cells.

Preoptic formation of 17β-oestradiol is influenced by behavioural stimuli in the dove

In vitro study of testosterone (T) metabolism shows that formation of 17β-oestradiol (E 2) in the preoptic area is higher in male doves exposed to behavioural stimuli from interacting pairs than in visually isolated males or males that have interacted with females. Formation of 5α-dihydrotestosterone, 5β-dihydrotestosterone and 5β-androstane-3α,17β-diol was similar in all groups, indicating that exposure to stimuli from interacting pairs influences aromatization of T and not other pathways of androgen metabolism. The results suggests that sexual stimuli, which do not involve tactile cotact between male and female, affect local E 2 formation in the brain.

Identification of androgen metabolic pathways in the brain of little brown bats (Myotis lucifugus): sex and seasonal differences.

During the reproductive cycle of the little brown bat (Myotis lucifugus), the display of sexual behavior is out of synchrony with maximal gonadal development, suggesting that changes in plasma hormone levels per se are not the primary determinants of neural responsiveness. In the present study, we investigated pathways of androgen metabolism in the brain of the bat and compared brain aromatase activity in spring and in autumn. Tissue homogenates were incubated with [3H] androstenedione in the presence of an NADH/NADPH-generating system, and radiolabeled products isolated and their authenticity verified by recrystallization to constant specific activity. Aromatase was identified in preoptic/hypothalamic and adjacent limbic areas, and 5 alpha-reductase was detected in all major brain divisions. No gender-based differences in brain aromatase were seen in spring just prior to emergence from hibernation; however, activity was greater in males than in females when measured during maximal breeding activity in autumn. In addition, seasonal changes were evident in the preoptic/hypothalamic regions of both sexes (spring greater than autumn), although estrone yields from limbic tissues remained constant. Thus, in seasonally breeding species, the rate at which circulating androgen is converted to estrogen or other biologically active metabolites in the brain itself may be an important determinant of behavioral or feedback responsiveness.

In vitro aromatization and other androgen transformations in the brain of the hamster (Mesocricetus auratus).

Pathways of androgen metabolism were studied in hamster brain to determine whether the actions of circulating androgens on behavior and neuroendocrine responses could be mediated by conversion to estrogen or other metabolites. Anterior limbic cortex (LIM), preoptic area/hypothalamus (POA/HTH), frontal cerebral cortex, gonads and muscle were pooled from 4 groups of animals: control males and females and blinded males and females. Tissue homogenates were incubated for 60 mm at 37#{176}C with I3Hl-androstenedione in the presence of an NADH-NADPH generating system. After extraction and chromatography, products were identified by reverse isotope dilution and recrystallization to constant specific activity. Estrone (E,) was synthesized in incubates of LIM and POA/HTH from all 4 groups; ovarian tissue synthesized both E, and estradiol-1 7(3 (E2 jl). No aromatase activity was detectable in cerebral cortex, muscle or testis. All brain and ovarian incubates contained Sa-androstane-3 , 1 7-dione but a 5(3-reduced metabolite, 5j3-androstane-3 17dione was present in even larger amounts. No 17(3- or 1 7a-oxidoreductase activity was identified in brain samples in these experiments; however, substantial quantities of radioactivity, possibly polyhydroxylated androgens, remained unidentified. These experiments demonstrate that aromatase and 5o-reductase, 2 enzymes leading to the synthesis of biologically active metabolites, are present in steroid target areas of the hamster CNS. Further, substantial 5(3-reductase activity is present, although a biological function for 5(3-reduced androgens in this species has not been reported.