IN-SITU HYBRIDIZATION OF LUTEINIZING-HORMONE HUMAN CHORIONIC-GONADOTROPIN RECEPTOR MESSENGER-RIBONUCLEIC-ACID DURING HORMONE-INDUCED DOWN-REGULATION AND THE SUBSEQUENT RECOVERY IN RAT CORPUS-LUTEUM
H. Peegel et al., IN-SITU HYBRIDIZATION OF LUTEINIZING-HORMONE HUMAN CHORIONIC-GONADOTROPIN RECEPTOR MESSENGER-RIBONUCLEIC-ACID DURING HORMONE-INDUCED DOWN-REGULATION AND THE SUBSEQUENT RECOVERY IN RAT CORPUS-LUTEUM, Endocrinology, 135(3), 1994, pp. 1044-1051
Previous studies have shown that injection of a pharmacological dose o
f hCG to rats primed with PMSG/hCG results in a loss of hCG binding in
the luteinized ovary, which is closely coupled with the loss of LH/hC
G receptor (LH/hCG R) messenger RNA (mRNA). The time course of down-re
gulation of the receptor mRNA reveals that mRNA totally disappears 24
h after the hormone injection, but fully recovers by 72 h. The purpose
of this study was to determine by in situ hybridization whether the r
ecovery of the receptor mRNA occurs in preexisting or newly formed cor
pora lutea. Twenty-one-day-old female rats were treated with 50 IU PMS
G, followed 56 h later by a single injection of hCG. On day 5 after th
e hCG injection, one group of rats was treated with a desensitizing do
se of hCG, and a control group received saline. The ovaries were colle
cted 6, 12, 24, 48, 72, and 96 h after the treatments and were process
ed for in situ hybridization using S-35 antisense RNA synthesized from
a 750-mer LH/hCG-R complementary DNA. In control ovaries, heavily lab
eled LH/hCG-R mRNA-containing cells were observed in the numerous corp
ora lutea. Ribonuclease pretreatment of the sections eliminated the si
gnal, and no specific hybridization was observed when sense strand pro
be was used. No hybridization to the granulosa cells was seen. Some hy
bridization occurred to the theca interna, but the intensity was lower
than that in the corpora lutea. Time-course studies showed a marked d
ecline in the hCG-R mRNA signals in corpora lutea as early as 6 h afte
r hCG injection, with a maximum loss of receptor mRNA by 24 h. After 4
8 h, hCG-R mRNA reappeared in preexisting corpora lutea, with the inte
nsity of the hybridization signal equaling that in corpora lutea of co
ntrols. New corpora lutes could not be identified at any time after in
jection of the down-regulating dose of hCG. As down-regulated receptor
mRNA recovered in preexisting, not new, corpora lutes, hormone-induce
d loss of luteal cell receptors would appear to be reversible.