Pathways for androgen biosynthesis in monkey testis

Hoschoian, J.C.; Brownie, Alexander C.

doi:10.1016/0039-128x(67)90018-9

Cited by 30 publications

(8 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is consistent with previous reports that the A5-pathway for testosterone bio¬ synthesis in testis is the dominant one in dog (Van der Molen & Eik-Nes 1971), bovine (Kahnt et al 1961), monkey (Hoschoian & Brownie 1967), and human (Yanaihara & Troen 1972), while the A4-pathway seems dominant in marmoset Saquinus oedipus (Preslock & Steinberger 1978), mouse (Ellis & Barliner 1965), and rat (Shikita & Tamaoki 1965;Slaunwhite & Burgett 1965). The marked inhibition by testosterone of the lyase activity for 17a-hydroxypregnenolone suggests that testoste¬ rone may play a physiologic role in feedback con¬ trol of testosterone biosynthesis in the human testis.…”

Section: Discussionsupporting

confidence: 94%

Studies of the human testis. XIV. Properties of C17-C20 lyase

Hosaka

Oshima

Troen

1980

Acta Endocrinologica

View full text Add to dashboard Cite

The properties of C17-C20 lyase in the human testis were investigated using a microsome fraction in the presence of NADPH. Michaelis constants (Km) of the enzyme were 1.7 \m=x\10\m=-\5m for 17\g=a\-hydroxyprogesterone and 5.9 \m=x\10\m=-\7 m for 17\g=a\-hydroxypregnenolone. Km of the lyase for NADPH were determined as 6.3 \ m=x\ 10 \ m=-\ 6 m in the presence of either 17\g=a\-hydroxyprogesterone or 17\g=a\-hydroxypregnenolone. In both instances, the maximum velocity (Vmax) of the lyase for 17\g=a\-hydroxyprogesterone was approximately two times higher than that for 17\g=a\-hydroxypregnenolone.Optimal pH and temperature of the enzyme for both 17\g=a\-hydroxyprogesterone and 17\g=a\-hydroxypregnenolone were 7.7 and 40\s=deg\C, respectively. Each steroid substrate inhibited competitively the lyase activity for the other with inhibition constants (Ki) of 1.9 \m=x\10\m=-\5 m for 17\g=a\-hydroxyprogesterone and 6.0 \m=x\10\m=-\7 m for 17\g=a\-hydroprogesterone and 20\g=a\-dihydropregnenolone showed non-competitive inhibition of the lyase for either 17\g=a\-hydroxyprogesterone or 17\g=a\-hydroxypregnenolone. In contrast, testosterone inhibited the enzyme activity for 17\g=a\-hydroxyprogesterone competitively, but revealed typical uncompetitive inhibition of the lyase for 17\g=a\-hydroxypregnenolone. Similarly, the inhibition of the lyase by 5-androstenediol was competitive for 17\g=a\-hydroxyprogesterone and of the mixed type for 17\g=a\-hydroxypregnenolone. Furthermore, oestradiol-17\g=b\ was found to be a competitive inhibitor of the lyase for 17\g=a\-hydroxyprogesterone,

show abstract

Section: Discussionsupporting

confidence: 94%

Studies of the human testis. XIV. Properties of C17-C20 lyase

Hosaka

Oshima

Troen

1980

Acta Endocrinologica

View full text Add to dashboard Cite

show abstract

“…Results from in vitro incubation experiments and percursor studies have yielded conflicting evidence on the relative contributions of the AA and As biosynthetic pathways to testosterone synthesis in the rhesus monkey testis, and under in vivo condi¬ tions the role of individual steroid precursors for testosterone has not been conclusively investigated. Hoschoian 8c Brownie (1967) demonstrated the utilisation of the A5 pathway in incubation studies with rhesus testis homogenates (Hoschoian 8c Brownie 1967;Brownie 8c Hoschoian 1967), whereas Sharma et al (1967) demonstrated preferential conversion of progesterone to 17-hydroxyprogesterone and to tes¬ tosterone under similar in vitro experimental conditions. Aso et al (1976) have measured basal peripheral concentrations of unconjugated steroids in the male rhesus monkey, but without dynamic testing of the adrenals and gonads, this approach can yield little information on the in vivo biosynthesis of testosterone.…”

mentioning

confidence: 92%

Serum Levels of Testicular and Adrenal Steroids After Dexamethasone and HCG-Administration in the Laboratory-Maintained Rhesus Monkey

Wickings¹,

Nieschlag²

1978

Acta Endocrinologica

View full text Add to dashboard Cite

In order to evaluate the endocrine testicular and adrenal function of rhesus monkeys in vivo, and to compare this with the human situation, the effect of dexamethasone (Dxm), HCG and combined Dxm/HCG administration on the steroid levels was investigated in 8 adult male rhesus monkeys in November/December (= season of high testicular activity). Serum levels of cortisol, testosterone (T), androstenedione (A), 17-hydroxyprogesterone (17-OHP), oestradiol (Oe2), dehydroepiandrosterone (DHA) and its sulphate (DHA-S) were measured radioimmunologically.Basal T and DHA serum levels were similar to those found in man, whilst A levels amounted to 1/10 and DHA-S to 1/30 of human values.Oe2 and 17-OHP levels were higher than in man. T and A levels were not suppressed by Dxm and very high degrees of stimulation were reached after HCG. The HCG-induced increment in T was smaller under Dxm/HCG than under HCG alone. 17-OHP levels were reduced to 25% of basal levels under Dxm, but the incremental response to Dxm/HCG was the same as that without Dxm. DHA and DHA-S were 60 and 75 % lower under Dxm, and the increment in DHA after Dxm/HCG was less than that after HCG. DHA-S did not respond to HCG.

show abstract

“…However, it was reported that for testosterone formation only the pathway from 5-021 steroid to A4-C21 steroid occurs in the testes of rats (Shikita et al 1964) and of other rodents (Tamaoki, Inano & Nakano, 1969). The pathway from the A5-C21 steroid to the A5-C19 steroid was reported for testosterone formation by the dog (Eik-Nes & Kekre, 1963) and rhesus monkey testes (Hoschoian & Brownie, 1967). So far the 4-and A5-routes from pregnenolone to testosterone in gallinaceous birds such as the domestic fowl and the Japanese quail have not been found in other vertebrates.…”

Section: Discussionmentioning

confidence: 94%

Pathways for Androgen Synthesis in Vitro by the Testes of Japanese Quail (Coturnix Coturnix Japonica)

Nakamura¹,

Tanabe²

1972

Journal of Endocrinology

View full text Add to dashboard Cite

The microsomal fraction of testicular tissue from Japanese quail (Coturnix coturnix japonica) was incubated with 4-14C-labelled pregnenolone, progesterone, 17\g=a\-hydroxyprogesterone,androstenedione, dehydroepiandrosterone and testosterone and [7-3H]17\g=a\-hydroxypregnenolone in a medium containing either NAD or NADPH. The metabolic products were identified by their mobilities on thin-layer chromatograms, derivative formation after oxidation and acetylation of the metabolites, and recrystallization to constant specific activity.Three pathways for testosterone formation by the testes are suggested by the results: the first via progesterone, 17\g=a\-hydroxyprogesterone and androstenedione; the second via 17\g=a\-hydroxypregnenolone,dehydroepiandrosterone and androstenedione; and the third via 17\g=a\-hydroxypregnenolone, dehydroepiandrosterone and androst-5-ene-3\g=b\,17\g=b\-diol.

show abstract

Pathways for androgen biosynthesis in monkey testis

Cited by 30 publications

References 17 publications

Studies of the human testis. XIV. Properties of C17-C20 lyase

Studies of the human testis. XIV. Properties of C17-C20 lyase

Serum Levels of Testicular and Adrenal Steroids After Dexamethasone and HCG-Administration in the Laboratory-Maintained Rhesus Monkey

Pathways for Androgen Synthesis in Vitro by the Testes of Japanese Quail (Coturnix Coturnix Japonica)

Contact Info

Product

Resources

About