Archive for the ‘Luteinizing Hormone’ Category

Modulatory Role for Substance P: DISCUSSION(6)

Thus, in addition to differences in the pattern and duration of the treatments applied, it should be noted that static incubations were carried out using cells cultured in monolayer whereas superfusion studies were carried out on pituitary fragments, in which cell-to-cell communication could conceal the synergistic interaction. buy ortho tri-cyclen online

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Modulatory Role for Substance P: DISCUSSION(5)


The dynamics of the effects of SP and/or GnRH on LH release were investigated by using a superfusion system in which pulsatile GnRH administration resembles the in vivo situation more closely than in static cultures of pituitary cells. Under these conditions, three successive pulses of GnRH or SP clearly stimulated LH release by anterior pituitary fragments, although a slight, but significant, decrease of the magnitude of the response was observed after the first pulse.

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Modulatory Role for Substance P: DISCUSSION(4)

Thus, binding of SP to NK1 receptors would activate PLC-mediated hydrolysis of inositol phospholipids, which would be followed by an increase in cytosolic free Ca2+. Hence, it seems unlikely that the synergistic interaction between SP and GnRH is exerted through cross-talk between distinct second messengers. In contrast, potentiation of GnRH-induced LH release by NPY is associated with an increase in the binding affinity of GnRH to gonadotrophs, which has been suggested also to involve unmasking of “cryptic” GnRH receptors. buy levaquin online
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Modulatory Role for Substance P: DISCUSSION(3)


In addition to its ability to increase basal LH secretion, we have found that SP potentiates the stimulatory action of GnRH on LH release from porcine pituitary cells in static culture during a 4-h coincubation. In rats, analysis of the effects of SP on GnRH-induced LH release has led to contradictory results. Thus, whereas some authors have reported that SP at low concentrations potentiates, and at high doses inhibits, the GnRH stimulatory effect, others have found no effect or an inhibitory effect of SP in this regard. asthma inhalers

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Modulatory Role for Substance P: DISCUSSION(2)

It has been suggested that conformational and structural similarities between SP and GnRH could allow the neuropeptide to interact with the GnRH receptor. In fact, high concentrations of SP can displace [125I]GnRH binding in membrane preparations of rat pituitary tissue. To ascertain whether the stimulatory effect of SP on LH release from porcine gonadotrophs involved activation of GnRH receptors, we examined the influence of the potent GnRH antagonist antide on gonadotropin secretion in response to SP. buy ampicillin
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Modulatory Role for Substance P: DISCUSSION(1)

DISCUSSION(1) An emerging body of evidence derived from morphological, biochemical, and physiological studies suggests that SP can play a relevant role in the regulation of the hypothalamo-gonadotropic axis. However, there is a dearth of information on the effects that SP can exert on gonadotrophs from species other than the rat. Likewise, the possible interaction of SP with GnRH, the main factor controlling gonadotroph function, has hitherto received little attention. In the present study, we provide unequivocal evidence that SP stimulates LH release from cultures of porcine gonadotrophs and that this effect is not mediated via a GnRH receptor. Furthermore, we show that under certain conditions SP can enhance the stimulatory effect of GnRH on LH secretion.
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Modulatory Role for Substance P: RESULTS(3)

Effect of SP on pLH Secretion by Porcine Pituitary Fragments in Superfusion A superfusion system was employed to analyze the dynamics of the response of porcine gonadotrophs to SP and/or GnRH treatment. After 8-10 h of superfusion, stable baseline levels of pLH secretion were observed, with mean values for control chambers of 128.7 ± 10.7 ng LH/ml per 105 cells. Figure 5 depicts representative pLH secretory profiles from porcine pituitary fragments in response to pulsatile infusions (for 20 min every 2 h) of 100 nM GnRH, 1 |л,М SP, or a combination of both peptides. In all treatments, a maximum LH peak amplitude was reached 20 min after application of the secretagogue; then LH release declined progressively toward basal levels over the next 60 inin.
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