Prolactin Inhibits Annexin 5 Expression and Apoptosis in the Corpus Luteum of Pseudopregnant Rats: Involvement of Local Gonadotropin-Releasing Hormone

• Published in: Endocrinology (Philadelphia) Vol. 144; no. 8; pp. 3625 - 3631
• Main Authors: Kawaminami, Mitsumori, Shibata, Yutaka, Yaji, Akiko, Kurusu, Shiro, Hashimoto, Inoru
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Endocrine Society 01.08.2003
• Subjects: Animals; Annexin A5 - analysis; Annexin A5 - genetics; Apoptosis - drug effects; Biological and medical sciences; Blotting, Northern; Bromocriptine - pharmacology; Corpus Luteum - chemistry; Corpus Luteum - cytology; Corpus Luteum - drug effects; Dopamine Agonists - pharmacology; Female; Fundamental and applied biological sciences. Psychology; Gene Expression - drug effects; Gonadotropin-Releasing Hormone - analogs & derivatives; Gonadotropin-Releasing Hormone - antagonists & inhibitors; Gonadotropin-Releasing Hormone - pharmacology; Gonadotropin-Releasing Hormone - physiology; Immunohistochemistry; In Situ Nick-End Labeling; Prolactin - pharmacology; Prolactin - physiology; Pseudopregnancy; Rats; Rats, Wistar
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.2003-0118

We investigated a specific relationship between the expression of annexin 5 and prolactin in the corpus luteum of pseudopregnant rats, with particular interest in GnRH and apoptosis of luteal cells. The expression of ovarian annexin 5 mRNA was significantly decreased at mid-pseudopregnancy and recovered at the end, whereas it remained low on the corresponding day of pregnancy. The dopamine agonist CB-154, administered at mid-pseudopregnancy (d 5), increased ovarian annexin 5 mRNA, whereas prolactin, given daily for 3 d to cycling rats, decreased it. An immunocytochemical study also showed that annexin 5 increased in the corpus luteum on d 6 and 7 of pseudopregnancy after treatment with CB-154 on d 5. The distribution of annexin 5-positive cells was not uniform in the corpus luteum and matched that of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL)-positive cells. Because GnRH stimulates annexin 5 mRNA expression in the gonadotropes, involvement of the GnRH receptor was examined. Local administration of a GnRH antagonist, Cetrorelix, to hemilateral ovarian bursa of pseudopregnant rats simultaneously receiving CB-154 abrogated both the expression of annexin 5 and the TUNEL reaction. The present results clearly demonstrate that prolactin decreases annexin 5 mRNA in the luteal cells during pseudopregnancy. Prolactin is suggested to suppress the local action of GnRH, which stimulates annexin 5 synthesis and apoptosis of functional luteal cells during pseudopregnancy.