65 research outputs found
The function of oestradiol and its receptor in the rat testis
The testis consists of 2 different tissues i.e. the
interstitial tissue, which is the site of steroidogenesis,
and seminiferous tubules where spermatogenesis occurs.
Testosterone production takes place in the Leydig cells
of the interstitial tissue and is under the influence of
the tropic hormone LH. The action of LH is initiated
by interaction with specific receptors located on the cell
membrane of the interstitial cells. Binding to the
receptor leads to a stimulation of cAMP production
and this in turn leads to an activation of cAMP dependent
protein kinases. The obligatory function of cAMP in the
stimulation of testosterone production can be questioned
since cAMP production is undetectable with doses of LH which
result in maximum steroidogenesis. The role of protein
kinase seems more clear since a correlation exists between
protein kinase activation and stimulation of testosterone
production. The involvement of protein synthesis in the
mechanism of action of LH was confirmed by the discovery of
the synthesis of a specific protein after LH stimulation and the inhibition of testosterone production by protein
synthesis inhibitors
Effects of Oestrogens and FSH on LH Stimulation of Steroid Production by Testis Leydig Cells from Immature Rats
Hypophysectomy of immature male rats results after 5 days in a decreased production of testosterone by isolated testis Leydig cells in response to LH. The LH responsiveness of the Leydig cells can be partly restored by treatment of the hypophysectomized rats with FSH. In continuation of previous reports on this subject (Steroids 28 (1976) 847; and 30 (1978) the following conclusions were derived from the results in the present paper: 1. After hypophysectomy of immature male rats the production of testosterone (T) as well as of 5âpregnenolone (Î5P) by isolated Leydig cells in response to LH is reduced. 2. Daily administration of FSH after hypophysectomy restores the Î5P production in response to LH almost completely, but has a much smaller effect on the restoration of T production. 3. Administration of oestradiol benzoate (E2B) together with FSH has no effect on the restoration of LHâstimulated Î5P production, but causes a reduction of T production, when compared with Leydig cells from animals treated with FSH only. 4. Treatment of intact immature rats with E2B results in a decreased production of T and an increased production of Î5P in isolated Leydig cells. 5. From experiments with labelled pregnenolone it appears that E2B and diethylstilboestrol (DES) inhibit the 17αâhydroxylase activity of Leydig cells from intact as well as from hypophysectomized rats. This results in a reduced conversion of pregnenolone to C1:)âsteroids and in increased production of 3αâhydroxyâ5αâpregnanâ20âone from ÎŽ5P. 6. The observed effects of FSH and E, were similar within a dose range of 100â10000 ng LH per 106 Leydig cells. Copyrigh
Metodologia para teste de tetrazĂłlio em sementes de Amburana cearensis (AllemĂŁo) A.C. Smith
Sensitivity of seed to desiccation in cupuassu (Theobroma grandiflorum (Willd. ex Spreng.) K. Schum. - sterculiaceae
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