Luteinizing Hormone‐Releasing Hormone Receptor Messenger Ribonucleic Acid Expression in the Rat Pituitary during Lactation and the Estrous Cycle

Abstract

To study mechanisms underlying the modulation of luteinizing hormone-releasing hormone receptor (LHRH-R) during lactation and the estrous cycle, we used a reverse transcriptase-polymerase chain reaction (RT-PCR) procedure to generate a probe for rat LHRH-R messenger RNA (mRNA). Using primers based on the mouse sequence, we amplified an approximately 300 bp fragment from rat pituitary complementary DNA. This PCR product was shown to be part of LHRH-R cDNA by direct sequencing and by comparing to the rat LHRH-R cDNA reported recently. Then, this PCR fragment was used as a probe for northern blotting analysis. The level of LHRH-R mRNA in the pituitary was significantly decreased during lactation, by approximately 80%, compared to that of ovariectomized and intact (diestrous and metestrous cycling) rats while no statistical difference in glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) mRNA level was observed between groups. During the estrous cycle, the level of LHRH-R mRNA in the pituitary was about two-fold higher on diestrous day 2 and the morning of proestrus than that on diestrous day 1 and quickly returned toward control level by noon of proestrus. In addition, we found that GAPDH mRNA levels from a so-called housekeeping gene often thought to be unchanged under different conditions, were significantly higher on proestrus while levels of 18S rRNA were not significantly changed. The large decrease in LHRH-R mRNA during lactation could account for the changes in LHRH binding previously reported.

Effects of long-term treatment with the luteinizing hormone-releasing hormone (LHRH) agonist Decapeptyl and the LHRH antagonist Cetrorelix on the levels of pituitary LHRH receptors and their mRNA expression in rats

“…However, in the previous study (28), the control rats were killed in estrus as compared with controls in diestrus II in this experiment. There is no discrepancy between our present and previous findings because it has been reported that in normal rats in diestrus II, the LHRH-R mRNA levels are 2-3 times higher than in estrus (39,40). The elevation of LHRH-R mRNA in the normal female rats after the daily Decapeptyl treatment found in this study was accompanied by a 2.2-fold rise of LHRH-R protein levels.…”

GnRH Antagonist-induced Down-regulation of the mRNA Expression of Pituitary Receptors: Comparisons with GnRH Agonist Effects

“…Levels of LHb subunit mRNA were determined by Northern blotting with the probe for LHb-subunit (5'-GCCGGCACAGATGCTGGTGGTGAA-3') which was end-labeled with [r-32P]ATP using T4 polynucleotide kinase as described previously [2]. Levels of GnRH-R mRNA were determined by Northern blotting with 32 Plabeled GnRH-R single-stranded DNA probes as described previously [4]. The sequences of primers are as follows: N-primer: 5'-GCCAAAATCATCTTTGCTCTCACG-3' C-primer:…”

Ovariectomy-Evoked Increase in Gonadotropin Releasing Hormone Receptor Parallels Its Messenger RNA Level, but Does not Correlate with Stimulated Gonadotropin Release.

“…The concentrations of LH, follicle-stimulating hormone (FSH) and LH-fJ in sera and anterior pituitary extracts were measured with a double-antibody radioimmunoassay kit provided by NIDDK (Bethesda, MA, USA), and were expressed in terms of the NIDDK reference standards rLH-RP-2, rFSH-RP-1, and LH beta AFP-A805. Amount of GnRH-R mRNA and its binding capacity Figure 1A shows [14,15], where a decline in GnRH-R mRNA was found to be significant after ovulation; but these studies did not also investigate ligand binding by GnRH-R. After ovariectomy, GnRH-R binding had increased by 30% at 2 wk and by 70% at 4 wk. These changes paralleled receptor mRNA concentrations, which tendency is compatible with previous reports [16,17] .…”