Expression of lysophosphatidic acid receptors in the rat uterus: cellular distribution of protein and gestation-associated changes in gene expression

Though lysophosphatidic acid (LPA) shows a variety of regulatory roles in reproduction, its action mechanisms in the gestational organs are still largely unknown. We here characterized cellular distribution of its six kinds of specific receptors (LPA1-6) in rat uteri by immunohistochemistry and quantitatively analyzed changes in Lpar1-6 mRNAs expression throughout pregnancy. Among LPA1-6, evident expression of LPA3, LPA4, and LPA6 was immunologically detected and less expression of immunoreactive LPA1 and LPA2 was also found. Luminal and glandular epithelial cells, stromal cells, and myometrial cells are sites of positive immunoreactions, and they are all likely to express three or more subtypes. All of Lpar1-6 mRNAs were expressed, and their alterations were variable depending on subtypes and gestational age. The present information suggests that diverse actions of LPA in the uterus involve varied expression of LPA receptors dependent on tissue/cell types, receptor subtype(s), and organ reproductive states and helps to understand uterine biology of LPA.

Gonadotropin-releasing hormone stimulation of annexin A5 expression in the thymus of male rats

As gonadotropin-releasing hormone (GnRH) is expressed in the thymus, its direct action on thymic cells, including thymic involution, has been suggested. Annexin A5 (ANXA5), a biomarker of GnRH, was used to determine whether GnRH affects the thymus of male rats. Immunohistochemistry showed positive reactions for ANXA5 in large medullary epithelial cells at 30 days of age, and the expression continued until 180 days of age. Organ culture of thymus pieces was performed to examine the direct action of a GnRH agonist (GnRHa) on the expression of Anxa5 and Gnrh mRNA. Thymus tissues obtained from male rats (40–60 days old) were cut into small pieces (2–3 mm³) and incubated for 3 hr with the GnRHa. The expression levels of Anxa5 and Gnrh mRNA were augmented by the GnRHa. Immunohistochemistry of these tissue fragments showed that ANXA5 expression was enhanced, especially in medullary epithelial cells. These results revealed that GnRH synthesis in the thymus could affect thymic epithelial cells after puberty.