Evidence that human chorionic gonadotropin/luteinizing hormone receptor down-regulation involves decreased levels of receptor messenger ribonucleic acid.
Injection of pseudopregnant rats with pharmacological doses of hCG leads to a characteristic decrease in LH/hCG binding by the isolated luteal cells. The steady state levels of LH/hCG receptor mRNA were determined in rat ovaries during hCG-induced down-regulation of the receptor. Northern blots were performed using a 20-mer probe corresponding to a guanine cytosine-rich carboxyl-terminal untranslated region of the LH/hCG receptor cDNA. The hybridization of the probe to LH/hCG receptor mRNA was highly specific, since the probe hybridized only to rat luteal cell RNA fraction, with no signal detected in nontarget tissues. The LH/hCG receptor level was quantitated by [125I]hCG binding to the isolated membrane fractions from the corresponding treatment and control groups. Examination of mRNA levels of the receptor during hCG-induced down-regulation showed a steady decrease from 0-24 h, followed by a gradual increase to control levels from 24-72 h corresponding to days 8-9 of pseudopregnancy. The [125I]hCG-binding activity during down-regulation paralleled the mRNA profile in both the experimental and control groups. Examination of the levels of mRNA for alpha-actin showed no change during this period, suggesting that the loss of LH/hCG receptor mRNA at 24 h was not due to a general loss of mRNA in luteal cells. These results suggest that hCG-induced down-regulation of the LH/hCG receptor in luteal cells involves regulation of the receptors at the message level.
Hoffman
Y M
YM
Department of Obstetrics/Gynecology, University of Michigan Medical School, Ann Arbor 48109.
Peegel
H
H
Sprock
M J
MJ
Zhang
Q Y
QY
Menon
K M
KM
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002462:Cell Membrane / Q000378:metabolism; D006063:Chorionic Gonadotropin / Q000378:metabolism / Q000494:pharmacology*; D015536:Down-Regulation; D005260:Female; D007700:Kinetics; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D015345:Oligonucleotide Probes; D011555:Pseudopregnancy; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011974:Receptors, LH / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism
D006063:Chorionic Gonadotropin; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D011974:Receptors, LH