Effects of transferrin on aromatase activity in porcine granulosa cells in vitro.

Abstract

Abstract:Proliferating cells have an absolute requirement for iron, which is delivered by transferrin with subsequent intracellular transport via the transferrin receptor. Recent studies have reported that transferrin plays a crucial role in the local regulation of ovarian function, apart from its iron-binding characteristic. Therefore, the present study was undertaken to explore the possible role of transferrin in porcine granulosa cells function by examining its influence on aromatase activity, the most important indicator of follicular cell differentiation. In the first series of studies, pig granulosa cells isolated from small, immature follicles were cultured in the presence of transferrin alone (10 µg/ml or 100 µg/ml) or with the addition of FSH (100ng/ml). The second series of studies was undertaken to determine transferrin-stimulated granulosa cells ability to aromatize exogenous testosterone (1×10 -7 M). One hour after the establishment of cultures an aromatase inhibitor CGS16949A was added to test its influence on estradiol production. After 48 hours, cultures were terminated and cells were processed for immunocytochemical staining of aromatase. Media were frozen for further estradiol level analysis. Positive immunostaining for aromatase was found in all granulosa cell cultures. The intensity of immunostaining was always stronger in cultures supplemented with FSH whereas the addition of transferrin had no effect. Granulosa cells in vitro synthesized the highest amount of estradiol after the addition of FSH and exogenous testosterone as measured radioimmunologically. Concomitant treatment with FSH and transferrin caused an inhibition of FSH-stimulated aromatase activity. The production of estradiol also declined in the presence of FSH, testosterone and transferrin. This study demonstrates that transferrin had a dose-dependent inhibitory effect on FSH-stimulated aromatase activity, which was confirmed by radioimmunoassay. Our results indicate that transferrin may be an important factor in the regulation of granulosa cell diferentiation.

Effect of mono‐(2‐ethylhexyl) phthalate (MEHP) on proliferation of and steroid hormone synthesis in rat ovarian granulosa cells in vitro

“…To our knowledge, the inhibitory influence of MEHP on GCs viability observed in this study is the first demonstration that MEHP exerts an anti‐proliferative effect on rat ovarian GCs in a dose‐dependent manner. This finding implies that MEHP can block the ovarian cell cycle as proliferation and differentiation of GCs are essential for follicular development (Durlej, Duda, Knapczyk, & Słomczyńska, ). However, this needs to be confirmed by direct measurement of cell numbers in growing follicles in vivo.…”

Comparative Proteomic Analysis of Follicular Fluids from Normal and Cystic Follicles in Sows

“…(2003) suggested that bovine RBP‐4 expressed and synthesized in theca and GCs accumulates retinol and delivers it across the ovarian follicular basal lamina. As the most important indicator of follicular cell differentiation (Durlej et al. 2008), transferrin may regulate ovarian function.…”

Immunoexpression of aromatase cytochrome P450 and 17β-hydroxysteroid dehydrogenase in women’s ovaries after menopause

“…The key enzymes of ovarian steroidogenesis are hydroxylases and oxidases, which belong to a large family of cytochrome P450 [1-4] that consists of 480 enzymes, including i) P450scc, which is responsible for cleaving the side chain of cholesterol, ii) P450c11, which mediates the conversion of 11-deoxycorticosterone to corticosterone and possesses 11-hydroxylase, 18-hydroxylase, and 19-methylooxydase activities, iii) P450c17, which mediates 17-hydroxylation of pregnenolone and progesterone, iv) P450c21, which has 21-hydroxylase activity, and v) aromatase cytochrome P450, whose activity directs aromatisation of androgens to estrogens [4-8]. Steroidogenesis includes a few characteristic reactions such as i) side-chain cleavage as a result of desmolase activity, ii) conversion of hydroxyl groups to ketone groups mediated by dehydrogenase, and iii) addition of hydroxyl groups (hydroxylation) by a reaction involving the formation of double bonds (removing hydrogen atoms) and saturation (adding hydrogen atoms) [3,4].…”