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  • Title: The newly formed corpora lutea of normal cycling rats exhibit drastic changes in steroidogenic and luteolytic gene expressions.
    Author: Taketa Y, Yoshida M, Inoue K, Takahashi M, Sakamoto Y, Watanabe G, Taya K, Yamate J, Nishikawa A.
    Journal: Exp Toxicol Pathol; 2012 Nov; 64(7-8):775-82. PubMed ID: 21345661.
    Abstract:
    In normal estrous cycling rats, corpora lutea (CL) regress over several cycles; however, the period during which they secrete progesterone (P4) is strictly limited. In the present study, we clarified the function of CL in normal cycling rats. We especially focused on expression levels of four steroidogenic and two luteolytic genes in the two different populations of the CL (new and old CL) at each estrous stage. The ovaries of female rats at each estrous cycle were collected, and new and old CL were separated with laser microdissection and analyzed for mRNA expression. In the new CL, the expressions of scavenger receptor class B type I (SR-BI), steroidogenic acute regulatory protein (StAR), and P450 cholesterol side-chain cleavage (P450scc) mRNA reached their highest levels at metestrus, and 3β-hydroxysteroid dehydrogenase (3β-HSD) mRNA gradually increased from estrus to diestrus. Meanwhile, 20α-hydroxysteroid dehydrogenase (20α-HSD) and prostaglandin F2 alpha receptor (PGF2α-R) mRNA levels were remarkably low from estrus to metestrus and gradually increased thereafter. These gene levels in new CL corresponded to serum P4 levels during the estrous cycle. In the old CL, all steroidogenic and luteolytic gene levels were consistently high throughout the estrous cycle. These results provide clear evidence that new CL at metestrus have strong steroidogenic activity and through inhibition of luteolysis, maintain P4 production in normal cycling rats. The elevation of 20α-HSD and PGF2α-R levels in new CL at diestrus may be a trigger of functional luteolysis.
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