Bioactive follicle-stimulating hormone

Specific and sensitive in vitro bioassays suitable for measurement of follicle-stimulating hormone (FSH) in small quantities of serum and urine have recently been validated. Comparisons of bioassay (B-FSH) potencies with immunoassay (I-FSH) estimates and chromatofocusing patterns have facilitated new discoveries regarding the regulation of FSH biosynthesis, storage, secretion, serum concentrations and target cell responsiveness, plasma clearance, and the significance of excreted forms. A review of recent studies reveals that luteinizing hormone and FSH, as well as B-FSH and I-FSH, appear to be differentially regulated by GnRH, GnRH agonists and antagonists, sex steroids and gonadal peptides in both sexes, with significant differences between the sexes. The results support the overall hypotheses that the quality as well as the quantity of FSH are significant contributors to target cell signal transduction and that distinct FSH isoforms with different functional capabilities influence the expression of acute (ovulation) and chronic reproductive events.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29246/1/0000303.pd

Human N ‐acetylation genotype determination with urinary caffeine metabolites

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109862/1/cptclpt199059.pd

Progesterone modulation of gonadotropin secretion by dispersed rat pituitary cells in culture. IV. Follicle-stimulating hormone synthesis and release

Estradiol-treated, rat pituitary cells were studied to examine the effects of progesterone (P) on follicle-stimulating hormone (FSH) synthesis and secretion. Progesterone was administered prior to or concurrent with 3 h secretory challenges with either gonadotropin-releasing hormone (GnRH), the iontophore A23187, the protein kinase C activator phorbol 12, 13-myristate (PMA), or no secretagogue. Medium FSH levels and cell FSH stores were quantified by radioimmunoassay and bioassay. Acute (both parameters. Chronic P elevated total FSH levels even when no secretagogue was present.Studies with antiprogestins, 5[alpha]-dihydroprogesterone and 5[alpha]-reductase inhibitors revealed that this direct action of P depended on progestin receptor occupation but not on 5[alpha]-reduction. These studies indicate that P selectively increases bioactive and immunoactive FSH levels, presumably by increasing FSH synthesis, and characterize the time course and cellular mechanisms of this response. To accommodate for P modulation of total FSH levels, FSH secretion was standardized as the percentage of cellular stores available for release. Progesterone modulation of GnRH-stimulated FSH secretion was multiphasic, i.e. increased at 0-6 h, unchanged at 9 h and suppressed at 24 h. Acute and chronic exposures to P similarly modulated A23187-stimulated FSH release, whereas both P treatments increased PMA-stimulated FSH secretion. In these experiments P modulated luteinizing hormone secretion in parallel fashion, suggesting that common cellular mechanisms underlie peptidergic and steroidal regulation of the secretion of both gonadotropins.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30974/1/0000647.pd

Follicle-stimulating hormone signal transduction: Role of carbohydrate in aromatase induction in immature rat Sertoli cells

Receptor activated adenylate cyclase acts as a major transmembrane signalling system. It is widely accepted that upon binding to its receptor, follicle-stimulating hormone (FSH) activates the cAMP-dependent pathway which in turn mediates FSH-induced estradiol production in Sertoli cells. Studies utilizing several chemically derived variants of FSH have demonstrated that these variants bind to the FSH receptors with equal avidity but differ in their ability to activate cAMP-dependent pathways. Since cAMP is believed to be the second messenger responsible for FSH signal transduction, we tested two hypotheses: (1) that the effects of different oFSH variants on cAMP production and aromatase induction (as measured by estradiol production) would be in parallel; and (2) that deglycosylated ovine FSH (DG-oFSH) would antagonize the ability of intact oFSH to stimulate aromatase induction, similar to its reported antagonistic effect on cAMP production.Immature rat (7- to 10-day-old) Sertoli cells were cultured and the effects of several different oFSH variants on cAMP production and/or aromatase induction were tested. The variants tested were native oFSH, DG-oFSH, asialo oFSH (AS-oFSH), a recombinant of intact LH[alpha] and FSH[beta] ([alpha] + [beta]) and a recombinant of deglycosylated LH[alpha] and intact FSH[beta] (DG[alpha] + [beta]). Both native oFSH and [alpha] + [beta] recombinant at relatively large doses (10 ng) elicited a significant increase in extracellular cAMP accumulation as well as total cAMP production. In contrast, DG-oFSH did not produce an increase in cAMP even at 10-fold higher doses than native oFSH. Intracellular cAMP concentrations did not increase following stimulation with native oFSH, DG-oFSH or DG[alpha] + [beta].In contrast to the divergent effects of oFSH and DG-oFSH on cAMP production all variants of oFSH stimulated estradiol production from Sertoli cells albeit with varying potencies. The sensitivity (minimal effective dose) and ED50 (dose at which half maximal response is achieved) of the estradiol (E2) response curve to increasing concentrations of native oFSH were 0.025 +/- 0.01 and 0.33 +/- 0.05 ng, respectively. Asialo-oFSH (AS-oFSH) increased E2 production with a potency (comparative dose required for effect) similar to that of native oFSH. In contrast, there was a 10-fold reduction in potency of DG-oFSH (ED50 of 3.27 +/- 1.7 ng). The efficacy (maximum effect on aromatase induction) of native, DG and AS-oFSH were equipotent. Coincubation of DG-oFSH (0.005-100 ng) with oFSH (0.01-0.625 ng) demonstrated the inductive effects to be additive. In contrast to the reduced potency of DG-oFSH, DG[alpha] -- [beta] recombinants (0.156-160 ng) increased E2 production with a potency similar to that of the native oFSH.Our data suggest: (1) the effects of oFSH variants on cAMP production and aromatase induction are not always parallel; (2) DG-oFSH is a weak agonist and not an antagonist of oFSH-mediated aromatase induction; (3) the reduced potency of DG-oFSH must involve oligosaccharides internal to sialic acid; and (4) depleting the carbohydrate moiety on the [alpha] subunit alone may not be adequate to reduce the potency of oFSH to induce aromatase. Since DG-oFSH does not increase cAMP accumulation, but is able to induce aromatase, the FSH-mediated induction of aromatase may be transduced through other signal pathways. Alternatively, the maximal steroidogenic response may be induced by small, but undetectable, increases in intracellular cAMP concentrations or availability of segregated cAMP pools.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29186/1/0000239.pd

Pathophysiological features of the pulsatile secretion of biologically active luteinizing hormone in man

The development of an in vitro bioassay of high specificity, sensitivity and precision for the measurement of low circulating concentrations of biologically active glycoprotein hormones has offered exciting new insights into the in vivo secretion and metabolic clearance of luteinizing hormone (LH) in various pathophysiological states. Moreover, the most recent combined application of the rat interstitial cell testosterone (RICT) bioassay and a novel multiple-parameter deonvolution model has allowed investigators to dissect plasma concentration profiles of bioactive LH into defined secretory bursts, which have numerically explicit amplitudes, locations in time, and durations, and are acted upon by detenninable subject- and study-specific endogenous metabolic clearance rates. Here, we have: (i) reviewed the ability of the endogenous GnRH pulse signal to regulate the in vivo secretion of biologically active LH molecules as assessed in the RICT and by deconvolution mechanics; (ii) demonstrated that low-dose exogenous GnRH pulses effectively mimic spontaneous bioactive LH pulsatility; (iii) investigated the role of endogenous androgen and estrogen in modulating bioactive gonadotropin secretion in men and women; and (iv) described significant alterations in endogenous LH bioactivity in puberty and healthy aging.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27746/1/0000138.pd

Effects of follicular phase exercise on luteinizing hormone pulse characteristics in sedentary eumenorrhoeic women

OBJECTIVE Current studies reveal little regarding the Inception of exercise-induced LH changes during physical training. This study aimed to assess the susceptibility of the hypothalamic–pituitary axis to the acute physical stress of exercise in untrained, physically inactive women. The acute effects of submaximal endurance exercise upon the pulsatile LH secretion in the follicular phase were compared with those accompanying leisurely strolling for a similar time period. SUBJECTS All subjects were eumenorrhoelc, as determined by biphasic temperature patterns, detection of the urinary LH surge, and mid-luteal serum progesterone levels. Subjects were not physically active and had little history of strenuous exercise ( V o 2 max = 38·0 ± 1·8) (mean ± SEM) ml/kg/min). DESIGN All women completed a 13·5-hour pulsatility test which included three consecutive 20-minute runs on a treadmill at 50, 60 and 70% of the subjects’maximum oxygen uptake ( n = 16). Six of these same subjects completed a separate test on another occasion in which one hour of leisurely strolling was substituted for exercise. Blood was sampled every 10 minutes via an indwelling cannula for 4·5 hours before and 8 hours after one hour of exercise and or strolling. MEASUREMENTS A pulse algorithm (Pulsar) was used to quantify LH pulse characteristics. RESULTS Exercise produced no significant effects upon LH pulse frequency or mean serum LH concentration. However, exercise of moderate intensity caused a significant increase in LH pulse amplitude ( P < 0·05). Strolling produced no significant changes in LH secretion. CONCLUSION Acute exercise of moderate intensity in the follicular phase of untrained women is an insufficient stimulus to inhibit the GnRH pulse generator in the post-exercise period, yet may produce a slight stimulatory effect on the amount of LH released per pulsePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73507/1/j.1365-2265.1994.tb02794.x.pd

Association between umbilical cord glucocorticoids and blood pressure at age 3 years

<p>Abstract</p> <p>Background</p> <p>Animal data show that decreased activity of placental 11-beta-hydroxysteroid dehydrogenase type 2 (11β-HSD2), which potently inactivates glucocorticoids (e.g. cortisol) to inert forms (cortisone), allows increased access of maternal glucocorticoids to the fetus and 'programs' hypertension. Data in humans are limited. We examined in humans the association between venous umbilical cord blood glucocorticoids, a potential marker for placental 11β-HSD2 enzyme activity, and blood pressure at age 3 years.</p> <p>Methods</p> <p>Among 286 newborns in Project Viva, a prospective pre-birth cohort study based in eastern Massachusetts, we measured cortisol (<it>F</it>) and cortisone (<it>E</it>) in venous cord blood and used the ratio of <it>F/E </it>as a marker for placental 11β-HSD2 activity. We measured blood pressure (BP) when the offspring reached age 3 years. Using mixed effects regression models to control for BP measurement conditions, maternal and child characteristics, we examined the association between the <it>F/E </it>ratio and child BP.</p> <p>Results</p> <p>At age 3 years, each unit increase in the <it>F/E </it>ratio was associated with a 1.6 mm Hg increase in systolic BP (95% CI 0.0 to 3.1). The <it>F/E </it>ratio was not associated with diastolic blood pressure or birth weight for gestational age <it>z</it>-score.</p> <p>Conclusion</p> <p>A higher <it>F/E </it>ratio in umbilical venous cord blood, likely reflecting reduced placental 11β-HSD2 activity, was associated with higher systolic blood pressure at age 3 years. Our data suggest that increased fetal exposure to active maternal glucocorticoids may program later systolic blood pressure.</p