Absence of detectable chorionic gonadotropin subunit messenger ribonucleic acids in the rat placenta throughout gestation.
We hypothesized that if a CG similar in structure to other glycoprotein hormones was present in the rat placenta, then mRNAs encoding its subunits would be detectable. To investigate the possible presence of a CG in the rat, we attempted to detect mRNAs encoding the alpha- and CG beta-like subunits in the placentae of timed pregnant rats by sensitive blot hybridization analyses using cloned cDNAs encoding alpha- and beta-subunits of LH derived from rat pituitary mRNA. No subunit-specific mRNAs in placentae of pregnant rats at 4-21 days gestation were detected at either high or low stringencies of hybridization. However, under similar conditions, subunit-specific mRNAs were readily observed in total pituitary RNA of normal as well as ovariectomized rats. Moreover, hybridization with a cDNA for alpha-tubulin, a major component of the cytoskeleton, yielded easily detectable bands in rat placental RNA. In addition, hybridization analysis, under low stringency conditions, of restriction enzyme digests of rat genomic DNA with a rat LH beta-cDNA, which would detect LH beta subunit-like genes, suggests the presence of a single gene that, in fact, encodes the rat LH beta-subunit. We conclude that mRNAs encoding for proteins structurally homologous to rat LH subunits are absent in the rat placenta and that only a single LH beta-like gene is present in the rat. The luteotropic activity associated with the rat placenta must be related to a gonadotropin-like hormone whose structure is dissimilar from that of CG.
Carr
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Chin
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D000818:Animals; D006063:Chorionic Gonadotropin / Q000145:classification / Q000235:genetics*; D004586:Electrophoresis; D005260:Female; D005796:Genes; D007986:Luteinizing Hormone / Q000145:classification / Q000235:genetics; D008722:Methods; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D012313:RNA / Q000032:analysis / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D006063:Chorionic Gonadotropin; D012333:RNA, Messenger; D012313:RNA; D007986:Luteinizing Hormone