Estrogen Suppresses Retinaldehyde Dehydrogenase 1 Expression in the Anterior Pituitary Glands of Female Rats

Abstract

Abstract. Retinoic acid (RA) plays a critical role in cell growth and tissue development. RA is also a regulating factor of pituitary function. RA is synthesized from retinoids through oxidation processes. The oxidation of retinal to RA is catalyzed by the retinaldehyde dehydrogenases (RALDHs), including RALDH1, RALDH2 and RALDH3. Recently, we demonstrated that RALDH1 is expressed in the anterior pituitary glands of adult male rats. However, the expression of RALDH1 in the female pituitary gland and the regulation of RALDH1 expression have not been determined. Therefore, we examined the expression of RALDH1 mRNA in the pituitary glands of adult female rats. By in situ hybridization with digoxigenin-labeled cRNA probes and quantitative real-time PCR analysis, we found that the expression level of RALDH1 was significantly lower in estrus as compared to proestrus, metestrus and diestrus. RALDH1 mRNA levels increased after ovariectomy and decreased remarkably after a 1-week treatment with 17β-estradiol implants. Estradiol (0.01-100 µg per rat) dose-dependently decreased the expression of RALDH1 in the pituitary glands after 24 hours of subcutaneous administration. These results clearly show that RALDH1 mRNA expression is suppressed by estrogen. We speculate that the generation of RA is regulated by estrogen and that RA plays a role in the estrus cycle through paracrine and/or autocrine mechanisms in the anterior pituitary gland of female rats.

Effects of retinoic acid on growth hormone-releasing hormone receptor, growth hormone secretagogue receptor gene expression and growth hormone secretion in rat anterior pituitary cells

“…In previous studies, we reported that RA-synthesizing enzyme, retinaldehyde dehydrogenase 1, was expressed in folliculostellate cells and lactotrophs but not in somatotrophs [22,23]. In the present study, we found that RA increased Ghrh-r and Ghs-r gene expression and promoted GHRH-and ghrelin-induced GH release from isolated rat anterior pituitary cells.…”

Estrogen Receptor Alpha Regulates Retinaldehyde Dehydrogenase 1 Expression in Rat Anterior Pituitary Cells

“…For normalization, we also quantified β-actin using forward (5'-tGG CAC CAC ACt ttC tAC AAt GAG C-3') and reverse (5'-GGG tCA tCt ttt CAC GGt tGG-3') primers. gland of female rats [19]. our in vivo study indicated that estrogen is a candidate for regulator of RALdh1 expression in the pituitary, but the mechanisms that may be responsible for this effect are not understood.…”

“…this decrease in RALdh1 expression was observed in cells incubated with a 17β-estradiol concentration as low as 1 x 10 -14 M. Lieberman et al [29] reported a dose-dependent increase in prolactin synthesis at physiological concentrations of estradiol (1 x 10 -11 -1 x 10 -6 M) in a rat pituitary cell culture. We previously reported that RALdh1 mRnA expression in the pituitary gland of ovariectomized rats was suppressed after a single subcutaneous injection of 17β-estradiol: mRnA expression in response to 0.01, 0.1, 1, 10, and 100 μg of 17β-estradiol decreased by 13%, our recent work has shown that RALdh1 mRnA expression level in the pituitary gland is lower in female than in male rats [19]. Moreover, we observed that RALdh1 mRnA expression was lower in female rats treated with 17β-estradiol [19].…”

“…We previously reported that RALdh1 mRnA expression in the pituitary gland of ovariectomized rats was suppressed after a single subcutaneous injection of 17β-estradiol: mRnA expression in response to 0.01, 0.1, 1, 10, and 100 μg of 17β-estradiol decreased by 13%, our recent work has shown that RALdh1 mRnA expression level in the pituitary gland is lower in female than in male rats [19]. Moreover, we observed that RALdh1 mRnA expression was lower in female rats treated with 17β-estradiol [19]. In the present study, we confirmed that both RALDH1 mRNA transcription and protein production in the pituitary gland were lower after implantation of a 17β-estradiol-filled tube in male rats ( Fig.…”

Effect of retinoic acid on midkine gene expression in rat anterior pituitary cells

“…In situ hybridization was performed with digoxigenin (DIG)-labeled cRNA probes, as described in our previous report [9]. Antisense and sense cRNA probes of rat MK were synthesized by in vitro transcription with DIG RNA Labeling Mix (Roche Diagnostics, Penzberg, Germany) [10].…”