Inhibition of Endogenous Catecholamine Synthesis Augments Early Follicular Phase Luteinizing Hormone Secretion*

Abstract

The physiological role of catecholamines, particularly dopamine and norepinephrine, in the regulation of gonadotropin secretion in humans is unclear. We administered the tyrosine hydroxylase inhibitor alpha-methyl-p-tyrosine (AMPT, 500 mg at 800 and 1000 h) to five women in the early follicular phase of the menstrual cycle and compared LH secretion patterns to those in five untreated controls. Commencing at 800 h, blood was drawn every 15 min for LH and PRL measurements until 1600 h. AMPT elevated PRL concentrations (mean +/- SEM) from a baseline of 14.72 +/- 2.51 micrograms/L to a peak of 102.2 +/- 24 micrograms/L. LH concentrations [21.97 +/- 0.56 (AMPT) vs. 13.51 +/- 0.16 IU/L (control), P less than 0.0001], LH area under the curve [11014 +/- 1815 (AMPT) vs. 7009 +/- 404 IU.min/L (control), P = 0.05] and LH pulse amplitude [9.99 +/- 2.38 (AMPT) vs. 4.03 +/- 0.61 IU/L (control), P = 0.04] were all greater in the group in which catecholamine synthesis was inhibited. There was no difference in pulse frequency between the groups (7.4 +/- 0.51 vs. 6.6 +/- 0.24 pulses/8 h, P greater than 0.05). We conclude 1) inhibition of endogenous catecholamine synthesis augments LH levels in the early follicular phase, and 2) increased LH secretion during catecholamine synthesis inhibition is due, at least in part, to increased LH pulse amplitude but not increased LH pulse frequency.

Effect of noradrenaline and dopamine on progesterone and estradiol secretion of human granulosa cells

“…] Bódis, Department of Obstetrics and Gynecology, University Medical School of Pécs, H-7624Pécs, Édesanyák útja 17, Hungary Plosker et al (1) reported augmented LH levels after ae-methyl-p-tyrosine treatment in women. They con¬ cluded that increased LH secretion after inhibition of catecholamine synthesis was due to an increased LH pulse amplitude.…”

Alpha Adrenergic Neurons Inhibit Luteinizing Hormone Pulse Amplitude in Breeding Season Ewes1

“…To further complicate matters, steroid treatment shifts the response to NE from inhibition to stimulation in the rat [26,43], but this may reflect activation of neural mechanisms for induction of the LH surge [26]. On the other hand, humans may be similar to the sheep, because there is suggestive evidence that a,-adrenergic mechanisms inhibit LH pulse amplitude in women [44,45].…”

Development and validation of a liquid chromatography–tandem mass spectrometric method for the determination of α-methyltyrosine in human plasma

“…Previous studies have demonstrated that administration of AMT increases endogenous prolactin levels both in animals and humans [6][7][8][9]. Thus, measuring AMT concentrations in plasma could help establish AMT pharmacokinetics and also aid in potentially developing a pharmacoki- netic/pharmacodynamic (PK/PD) model between AMT and prolactin.…”