HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lakkakorpi, J T Articles by Rajaniemi, H J Search for Related Content PubMed PubMed Citation Articles by Lakkakorpi, J T Articles by Rajaniemi, H J

To elucidate the molecular mechanisms involved in the homologous regulation of LH/chorionic gonadotrophin (CG) receptors, the receptor and its mRNA levels were analysed in the same pseudopregnant rat ovarian samples after human (h)CG-induced down-regulation using a binding assay, ligand blotting, immunoblotting and Northern blotting together with the polymerase chain reaction (PCR). Treatment of the animals with 500 IU hCG resulted in a loss of ¹²⁵I-labelled hCG binding and the 90 kDa receptor on the ligand and immunoblots within 12 and 24 h respectively, followed by a transient partial recovery on days 4 and 5, while a distinct decline occurred only on day 7 in the controls. Northern blots of total ovarian RNA, as probed with a 293 bp AvaI/HindIII fragment from the extracellular domain of PCR-generated full-length rat LH/CG receptor cDNA, revealed six major mRNAs of 7·0, 4·2, 2·8, 2·0, 1·4 and 1·1 kb. The 4·2 kb mRNA, which was the most abundant, possibly encodes the 90 kDa receptor, while the smaller species probably represent alternatively spliced forms of the LH/CG receptor pre-mRNA, as also supported by the finding that PCR produced three cDNA bands of 2·1, 2·0 and 1·8 kb when oligomers derived from the N and C termini of rat LH/CG receptor cDNA were used as primers and rat ovarian total RNA as a template. Treatment with hCG led to the down-regulation of all six mRNAs in a fashion parallel to the changes in receptor protein. No smaller receptor components capable of binding radiolabelled hCG or receptor antibody appeared on the ligand or immunoblots prior to or during down-regulation or the subsequent transient period of up-regulation, suggesting that the smaller mRNA species are translated in minute amounts in vivo or are not translated at all. Laser densitometric analysis of the Northern blots revealed that the amounts of the four smallest mRNA species increased during the period of down-regulation in relation to the 4·2 kb mRNA, and correspondingly decreased during the subsequent period of up-regulation, indicating changes in the alternative splicing of the primary transcript. The data suggest that hCG-induced transient down-regulation of the LH/CG receptor results in part from down-regulation of its mRNA levels, and that changes in alternative processing of the receptor pre-mRNA may play a regulatory role in the expression of functional LH/CG receptor during down- and up-regulation.

This article has been cited by other articles:

				P. M. Apaja, J. T. Tuusa, E. M. Pietila, H. J. Rajaniemi, and U. E. Petaja-Repo Luteinizing Hormone Receptor Ectodomain Splice Variant Misroutes the Full-Length Receptor into a Subcompartment of the Endoplasmic Reticulum Mol. Biol. Cell, May 1, 2006; 17(5): 2243 - 2255. [Abstract] [Full Text] [PDF]

				H. Youn, Y. Koo, I. Ji, and T. H. Ji An Upstream Initiator-Like Element Suppresses Transcription of the Rat Luteinizing Hormone Receptor Gene Mol. Endocrinol., May 1, 2005; 19(5): 1318 - 1328. [Abstract] [Full Text] [PDF]

				E. Bjurulf, O. Toffia, G. Selstam, and J. I. Olofsson Luteolysis Induced by a Prostaglandin F2{alpha} Analogue Occurs Independently of Prolactin in the Rat Biol Reprod, July 1, 1998; 59(1): 17 - 21. [Abstract] [Full Text]