Expression and hormonal regulation of the high-density lipoprotein (HDL) receptor scavenger receptor class B type I messenger ribonucleic acid in the rat ovary.
Since cholesterol delivery to the ovary is an essential regulated step in steroidogenesis, mRNA levels for the Scavenger Receptor Class B Type I (SR-BI), a putative high-density lipoprotein receptor (HDL-R), were examined in response to tropic hormones and the luteolytic agent prostaglandin F2alpha (PGF2alpha). For this, the rat SR-BI cDNA was isolated and cloned. The results of this investigation revealed that a single SR-BI mRNA transcript of 2.4 kb was highly expressed in the rat adrenal, ovary, and testis. The SR-BI transcript was increased (twofold) in the immature rat ovary following pregnant mare's serum gonadotropin (PMSG) administration and in the ovary, 8 d after ovulation, in response to stimulation by human chorionic gonadotropin (hCG). In the ovary 8 d following ovulation, basal ovarian SR-BI mRNA levels were elevated up to sixfold relative to the preovulatory SR-BI mRNA levels. Even with the enhanced basal level of SR-BI mRNA within the ovary, hCG administration still resulted in a 2.5- (p < 0.025) and sevenfold (p < 0.01) increase in the 2.4-kb transcript, 3 and 6 h postinjection, respectively. This increase corresponded to a 58% increase in serum progesterone. In contrast, when PGF2alpha was administered, SR-BI mRNA levels were significantly reduced (3.5-fold; p < 0.01) in concert with a fourfold reduction (p < 0.001) in serum progesterone secretion. Furthermore, PGF2alpha blocked the hCG-induced increase in SR-BI mRNA levels when administered 30 min prior to hCG injection. The results of this study demonstrate that SR-BI mRNA levels are dramatically increased following exposure to gonadotropins in the ovary, whereas PGF2alpha exposure significantly reduced SR-BI mRNA levels.
McLean
M P
MP
Department of Obstetrics and Gynecology, University of South Florida College of Medicine, Tampa 33606, USA. mmclean@coml.med.usf.edu
Sandhoff
T W
TW
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018955:CD36 Antigens / Q000096:biosynthesis / Q000235:genetics*; D002352:Carrier Proteins; D006224:Cricetinae; D015237:Dinoprost / Q000494:pharmacology; D005260:Female; D006064:Gonadotropins, Equine / Q000494:pharmacology; D006801:Humans; D008075:Lipoproteins, HDL; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D010060:Ovulation; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein / Q000096:biosynthesis / Q000235:genetics*; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B
D018955:CD36 Antigens; D002352:Carrier Proteins; D006064:Gonadotropins, Equine; D008075:Lipoproteins, HDL; D008565:Membrane Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C495124:SCARB1 protein, human; C454739:Scarb1 protein, mouse; C495125:Scarb1 protein, rat; D051122:Scavenger Receptors, Class B; C031616:high density lipoprotein receptors; C075197:high density lipoprotein binding protein; D011374:Progesterone; D015237:Dinoprost