Measurement of testosterone by immunoassays and mass spectrometry in mouse serum, testicular, and ovarian extracts.

Accurate measurement of testosterone is important for reproductive endocrinology research, but the validity of direct (nonextraction) testosterone immunoassays, developed and validated for human serum, has not been appraised for application to mouse serum or steroidogenic tissue extracts. Testosterone was measured in serum and extracts of testis or ovary from male and female wild-type mice by 2 commercial direct testosterone immunoassays, with and without preassay extraction, and by the liquid chromatography, tandem mass spectrometry reference method. Results were compared hierarchically by correlation (Kendall's τ), regression (Passing-Bablok), and deviance (Bland-Altman) analysis, under the null hypothesis of perfect agreement between assays (slope = 1, intercept and deviation = 0).

Estradiol induction of spermatogenesis is mediated via an estrogen receptor-{alpha} mechanism involving neuroendocrine activation of follicle-stimulating hormone secretion.

Both testosterone and its nonaromatizable metabolite dihydrotestosterone (DHT) induce spermatogenesis in gonadotropin-deficient hpg mice. Surprisingly, because aromatization is not required, estradiol (E2) also induces spermatogenesis and increases circulating FSH in hpg mice, but the mechanism remains unclear. We studied E2-induced spermatogenesis in hpg mice on an estrogen receptor (ER)-alpha (hpg/alphaERKO) or ERbeta (hpg/betaERKO) knockout or wild-type ER (hpg/WT) background treated with subdermal E2 or DHT implants for 6 wk.

Sertoli cell androgen receptor DNA binding domain is essential for the completion of spermatogenesis.

We examined the biological importance of Sertoli cell androgen receptor (AR) genomic interaction, using a Cre-loxP approach to selectively disrupt the AR DNA-binding domain (AR-DBD). Sertoli cell (SC)-specific transgenic Abpa or AMH promoters targeted Cre-mediated inframe excision of mouse Ar exon-3, encoding the AR-DBD second zinc-finger (ZF2), generating SC-specific mutant AR(DeltaZF2) lines designated Abp.SCAR(DeltaZF2) and AMH.

Transgenic mutant D567G but not wild-type human FSH receptor overexpression provides FSH-independent and promiscuous glycoprotein hormone Sertoli cell signaling.

We have characterized the in vivo actions of human wild-type FSH receptor (FSHR) overexpressed in Sertoli cells of transgenic (Tg) mice (TgFSHRwt) compared with transgenic overexpression of the human activated mutant FSHR*D567G (TgFSHR*D567G). Testicular TgFSHRwt expression significantly elevated specific FSH binding (>2-fold, P < 0.01) relative to nontransgenic testes, similar to increased FSH binding in TgFSHR*D567G testes.

Maintenance of spermatogenesis by the activated human (Asp567Gly) FSH receptor during testicular regression due to hormonal withdrawal.

The first activating mutation of the FSH receptor (FSHR*D567G) was identified in a gonadotropin-deficient hypophysectomized man who exhibited persistent spermatogenesis and fertility with only androgen replacement. We have determined the ability of FSHR* activity to maintain spermatogenesis and/or steroidogenesis during gonadotropin and androgen deprivation in mature transgenic FSHR* mice (Tg(Abpa-FSHR*D567G)1Cmal), hereafter referred to as Tg-FSHR* mice. Testes of untreated adult Tg-FSHR* males were equivalent in weight to nontransgenic controls but exhibited increased total Sertoli cell (24%) and spermatogonia (34%) numbers and nonsignificantly elevated spermatocyte-spermatid numbers (13%-17%).

Perinatal testosterone surge is required for normal adult bone size but not for normal bone remodeling.

Although testosterone (T) has striking effects on mature skeletal size and structure, it is not clear whether this depends exclusively on adult circulating levels of T or whether additional early-life factors also play a role. We have compared the androgen-deficient hypogonadal (hpg) mutant mouse with intact, orchidectomized, and T-treated non-hpg mice to determine relative contributions of adult and perinatal T to bone growth and development. At 3 wk of age, although trabecular and cortical bone structure was normal, bone turnover was significantly altered in hpg male mice; osteoid volume (OV/BV) and osteoblast surface (ObS/BS) were significantly lower and osteoclast surface (OcS/BS) significantly higher in hpg mice compared with age-matched non-hpg mice, pointing to a role for the perinatal T surge in determining bone turnover levels before sexual maturity.

Gonadotropin control of inhibin secretion and the relationship to follicle type and number in the hpg mouse.

Inhibin is secreted in two distinct heterodimeric forms, A and B, but the mechanism for the differential control of these two forms is unclear. To evaluate the relationship between secretion of inhibin forms and folliculogenesis, the effects of gonadotropins on inhibin concentrations were studied in parallel with stereological enumeration of ovarian follicle types in gonadotropin-deficient hypogonadal (hpg) female mice treated with recombinant human FSH (10 IU/day), hCG (1 IU/day), or both for 20 days. Treatment with FSH alone significantly increased blood concentrations of both inhibin A and inhibin B, whereas hCG alone had no effect on either inhibin.

Complete Sertoli cell proliferation induced by follicle-stimulating hormone (FSH) independently of luteinizing hormone activity: evidence from genetic models of isolated FSH action.

Defining the gonadal effects of FSH distinct from those of LH remains difficult. We have characterized and compared the level of Sertoli and germ cell development in three mouse models recently created to isolate FSH activity from LH effects. Two models used LH-deficient hypogonadal (hpg) mice to selectively study either pituitary-independent transgenic (tg) FSH or ligand-independent activated tg FSH receptor (FSHR(+)) expression, and the third model used LH receptor (LHR)-deficient mice to isolate and examine endogenous mouse FSH effects.

Sertoli and germ cell development in hypogonadal (hpg) mice expressing transgenic follicle-stimulating hormone alone or in combination with testosterone.

We recently created a novel transgenic (tg) model to examine the specific gonadal actions of FSH, distinct from LH effects, by expressing tg-FSH in gonadotropin-deficient hypogonadal (hpg) mice. Using this unique in vivo paradigm, we now describe the postnatal cellular development in seminiferous tubules selectively stimulated by tg-FSH alone or combined with testosterone (T). In the alphabeta.

An activated human follicle-stimulating hormone (FSH) receptor stimulates FSH-like activity in gonadotropin-deficient transgenic mice.

FSH mediates its testicular actions via a specific Sertoli cell G protein-coupled receptor. We created a novel transgenic model to investigate a mutant human FSH receptor (FSHR(+)) containing a single amino acid substitution (Asp567Gly) equivalent to activating mutations in related glycoprotein hormone receptors. To examine the ligand-independent gonadal actions of FSHR(+), the rat androgen-binding protein gene promoter was used to direct FSHR(+) transgene expression to Sertoli cells of gonadotropin-deficient hypogonadal (hpg) mice.