Postnatal development of gastric aromatase and portal venous estradiol-17β levels in male rats

Abstract

Gastric parietal cells synthesize and secrete estradiol-17b (E 2 ) into gastric veins joining the portal vein, and a large amount of gastric E 2 first binds to its receptors in the liver. However, the role of the gastric E 2 is not entirely clear during postnatal development. The objective of this study was to reveal the onset of aromatase and other steroid-synthesizing enzymes in the gastric mucosa; to determine the period of rising E 2 levels in the portal vein; and to further understand the relationship between gastric E 2 and liver estrogen receptor a (ERa). The immunoblot bands and the immunohistochemistry of gastric mucosa revealed that aromatase protein began to express itself at 20 days and then increased in the levels of aromatase protein from 20 days onward. Expression of mRNAs for gastric aromatase (Cyp19a1) and other steroid-synthesizing enzymes, 17a-Hydroxylase (Cyp17a1) and 17b-hydroxysteroid dehydrogenase (HSD17b3), also increased similar to the increment of aromatase protein. Portal venous E 2 levels were elevated after 20 days and increased remarkably between 23 and 30 days, similar to gastric aromatase mRNA levels. The E 2 level was approximately three times higher at 40 days than that at 20 days. The liver weight and Esr1 levels began to increase after 20 days and the increment was positively correlated with the change of portal venous E 2 levels. These findings suggest that some changes may occur around 20 days to regulate the gastric E 2 synthesis and secretion.

Gastric estradiol-17β (E2) and liver ERα correlate with serum E2 in the cholestatic male rat

“…It has been reported that E 2 synthesis in the stomach starts to elevate after about 20 days in postnatal development male rats and these changes are positively correlated with the liver weight and the expression of Ers1 mRNA in the liver (Kobayashi et al 2013b). Thus, it is considered that gastric aromatase and portal E 2 play an important role in liver growth and/or function as well as in the BDL study.…”

“…Western blotting using PBS without first antibody as negative controls as well as immunohistochemistry were examined. All antibodies have been validated by several references, and these antibodies were used in our previous study in gastric mucosa of rats (Turner et al 2002, Omoto et al 2005, Firestein et al 2008, Kobayashi et al 2013b). …”

Beyond the X Factor: Relevance of Sex Hormones in NAFLD Pathophysiology

“…In males, the aromatase-dependent conversion of testosterone into estrogen exerts a key role in the sexual differentiation of the liver [ 39 ]. Notably, in rodents, aromatase has been found to be expressed and active in the gastric mucosa cells that secrete E2 in the portail vein [ 99 , 100 ], thus leading E2 to reach the liver and exert its regulatory action.…”

Intracrine Regulation of Estrogen and Other Sex Steroid Levels in Endometrium and Non-gynecological Tissues; Pathology, Physiology, and Drug Discovery

“…The stomach is an endocrine tissue, and in rodents it produces steroids starting at birth and throughout adulthood (Kobayashi et al, 2013 ). Human gastric mucosa expresses 17βHSD1, 2, 12 and AKR1C3/17βHSD5 (Table 7 ).…”