Pulsatile Luteinizing Hormone (LH) Release during the Progesterone-Induced LH Surge in the Female Rhesus Monkey*

Abstract

LH pulses during the progesterone (P)-induced LH surge were examined in ovariectomized and estrogen-treated female monkeys. Animals received a 2.5-mg P or oil injection 24 h after administration of 30 micrograms estradiol benzoate. The animals were fitted with jugular catheters connected to a tether-swivel system. Blood samples were collected at 10-min intervals starting 3-4 h before and ending 12-20 h after P or oil injection. Plasma LH was measured by both bioassay and RIA. LH pulses were determined by the PULSAR program. P administration induced a BIA-LH surge with a latency of 71 +/- 10 min in all seven animals. The P-induced bioassayable LH (BIA-LH) surge consisted of an ascending phase (204 +/- 24 min), a plateau period (174 +/- 32 min), and a descending phase (376 +/- 60 min). Oil injection did not cause a LH surge (n = 4). BIA-LH release before P and that during the P-induced LH surge were pulsatile. Pulse intervals of BIA-LH before P treatment (57.1 +/- 5.2 min) were not different from those before (55.0 +/- 11.7 min) and after (62.9 +/- 16.3 min) oil injection. In contrast, pulse intervals during the ascending phase (35.0 +/- 4.0 min), plateau period (34.6 +/- 2.6 min), and descending phase (45.0 +/- 3.1 min) were significantly shorter (P less than 0.02) than those before P. Pulse amplitudes of BIA-LH during the ascending phase (125.3 +/- 28.7 ng/ml) and plateau period (253.9 +/- 27.0 ng/ml) were significantly (P less than 0.001) higher than those (44.7 +/- 12.6 ng/ml) before P and during the descending phase (66.9 +/- 11.1 ng/ml). Radioimmunoassayable LH results were quite similar to those for BIA-LH, except that amplitude changes in radioimmunoassayable LH after P treatment were smaller than those in BIA-LH. It was concluded, therefore, that both the frequency and amplitude of pulsatile LH release increase during the P-induced LH surge, especially during the ascending phase and plateau period, in female rhesus monkeys. Furthermore, the present results support our previous conclusion that P facilitates pulsatile LHRH release with increases in frequency and amplitude in ovariectomized and estrogen-treated monkeys.

Episodic gonadotropin-releasing hormone gene expression revealed by dynamic monitoring of luciferase reporter activity in single, living neurons

“…G3 ϭ 0.50, G4 ϭ 0.50, and G5 ϭ 0.50. These values were selected because they corresponded to those employed by Terasawa et al (27) and Fox and Smith (28) for PULSAR analysis of luteinizing hormone levels and by Carnes et al (29) for ACTH pulse analysis.…”

The Alpha-1-Adrenergic Neuronal System Is Involved in the Pulsatile Release of Luteinizing Hormone-Releasing Hormone in the Ovariectomized Female Rhesus Monkey

“…LHRH pulses were detected by the Pulsar program [24] with cut-off criteria G i, G 2, G3, Ga, and Gj o f 3.8, 2.6, 1.9, 1.5, and 1 .2 , respectively, and with smoothing time equal to the length o f the experiment. Other parameters were similar to those described pre viously [25]. Pulse amplitude (peak value -trough value o f a pulse) and interpulse interval (the interval between peaks) were taken from the Pulsar report for each experiment.…”

Plasma Adrenocorticotropic Hormone in the Rat Demonstrates Three Different Rhythms within 24 h

“…A rhythm in plasma luteinizing hormone of similar frequency has long been regarded as a measure of hypothalamic activity [18,38,40].…”