Effect of retinoic acid on midkine gene expression in rat anterior pituitary cells
Access this Article
Retinoic acid (RA) is converted from retinal by retinaldehyde dehydrogenases (RALDHs) and is an essential signaling molecule in embryonic and adult tissue. We previously reported that RALDH1 was produced in the rat anterior pituitary gland and hypothesized that RA was generated in the gland. Midkine (MK) is an RA-inducible growth factor, and MK production in the rat anterior pituitary gland was recently reported. However, the mechanism that regulates gene expression of <i>MK</i> in the pituitary gland has not been determined. To investigate regulation of MK production in the anterior pituitary gland, we analyzed changes in <i>MK</i> mRNA in cultured rat anterior pituitary cells. We identified MK-expressing cells by double-staining with <i>in situ</i> hybridization and immunohistochemical techniques for RALDH1. <i>MK</i> mRNA was expressed in RALDH1-producing cells in the anterior pituitary gland. Using isolated anterior pituitary cells of rats, we examined the effect of RA on gene expression of <i>MK</i>. Quantitative real-time PCR revealed that 72 h exposure to a concentration of 10<sup>-6</sup> M of retinal and all-<i>trans</i> retinoic acid increased <i>MK</i> mRNA levels by about 2-fold. Moreover, the stimulatory effect of all-<i>trans</i> retinoic acid was mimicked by the RA receptor agonist Am80. This is the first report to show that RA is important in regulating <i>MK</i> expression in rat anterior pituitary gland.
- Endocrine Journal
Endocrine Journal 64(6), 633-638, 2017
The Japan Endocrine Society