Changing Frequency of Pulsatile Luteinizing Hormone and Progesterone Secretion During the Luteal Phase of the Menstrual Cycle of Rhesus Monkeys 1

Abstract

Experiments were conducted to examine the pulsatile nature of biologically active luteinizing hormone (LH) and progesterone secretion during the luteal phase of the menstrual cycle in rhesus monkeys. As the luteal phase progressed, the pulse frequency of LH release decreased dramatically from a high of one pulse every 90 min during the early luteal phase to a low of one pulse every 7-8 h during the late luteal phase. As the pulse frequency decreased, there was a corresponding increase in pulse amplitude. During the early luteal phase, progesterone secretion was not episodic and there were increments in LH that were not associated with elevations in progesterone. However, during the mid-late luteal phase, progesterone was secreted in a pulsatile fashion. During the midluteal phase (Days 6-7 post-LH surge), 67% of the LH pulses were associated with progesterone pulses, and by the late luteal phase (Days 10-11 post-LH surge), every LH pulse was accompanied by a dramatic and sustained release of progesterone. During the late luteal phase, when the LH profile was characterized by low-frequency, high-amplitude pulses, progesterone levels often rose from less than 1 ng/ml to greater than 9 ng/ml and returned to baseline within a 3-h period. Thus, a single daily progesterone determination is unlikely to be an accurate indicator of luteal function. These results suggest that the changing pattern of mean LH concentrations during the luteal phase occurs as a result of changes in frequency and amplitude of LH release. These changes in the pulsatile pattern of LH secretion appear to have profound effects on secretion of progesterone by the corpus luteum, especially during the mid-late luteal phase when the patterns of LH concentrations are correlated with those of progesterone.

Passive immunization with anti-oestradiol antibodies during the luteal phase of the menstrual cycle potentiates the perimenstrual rise in serum gonadotrophin concentrations and stimulates follicular growth in the cynomolgus monkey (Macaca fascicularis)

“…In our current experiments, we maintained LH pulse frequency at 1 pulse/h throughout the entire luteal phase, whereas in spontaneous menstrual cycles, the LH pulse frequency decreases to approximately 1 pulse every 4-8 h as the luteal phase progresses (Ellinwood et al, 1984). It is likely that the progressive decrease in LH pulse frequency during the spontaneous luteal phase is due to a deceleration of pulsatile GnRH secretion which is mediated by progesterone (Soules et al, 1984).…”

Absence of an Inhibitory Vasopressinergic Tone on LH Release in Pubertal Male Rhesus Macaques

“…Plasma concentrations of LH were measured in duplicate in 5- or 10-µl plasma aliquots with a Leydig cell bioassay [15] and results are expressed as nanograms NICHHD rhLH RP-1 (WDP-XV-20) per milliliter. Sensitivity of the assay was 0.1 ng LH with 10 µl; only an occasional sample fell below this level, and those points are plotted directly on the abscissa in the figures.…”

Liver X Receptor Modulation of Gene Expression Leading to Pro-Luteolytic Effects in Primate Luteal Cells.

“…In luteal cells, LH binds to its receptor and activates PKA [20], which is critical for maintaining primate luteal function. Toward the end of the primate luteal phase, LH pulses become less frequent in primates [21] and luteal LH sensitivity is diminished [14,22,23], potentially leading to enhanced LXRa (NR1H3) signaling due to decreased PKA activity. Indeed, luteal expressions of several known LXR target genes increase significantly (P , 0.05) following blockade of LH secretion and are returned to near control levels with LH replacement during the mid-late luteal phase of rhesus macaques, as determined via a previously published microarray database [24].…”