Both Ca2+-Protein Kinase C Pathway and cAMP-Protein Kinase A Pathway are Involved in Progesterone Production in FSH- and LH-stimulated Cumulus Cells during In Vitro Maturation of Porcine Oocytes

Abstract

Abstract:We investigated the role of cAMP-Protein kinase A pathway and Ca 2+ -Protein kinase C pathway w hich were activated by FSH and/or LH in the progesterone production by cumulus cells during in vitro m a t u r a t i o n o f p o r c i n e o o c y t e s . T h e l e v e l o f progesterone in the medium in which COCs had been cultured for 24 hr without FSH was 7.8 ± 1.5 ng/ml. The addition of FSH significantly increased the progesterone level in a dose-dependent fashion during 24-hr cultivation of COCs; a plateau was detected in 0.02 µg/ m l , b u t n o si g n i f i ca n t i n cr ea s e i n t h e l ev e l o f progesterone was observed in the medium in which COCs had been cultured for 24 hr with 1 or 10 µg/ml LH. When COCs were cultured with both 0.02 µg/ml FSH and 1.0 µg/ml LH for 24 hr, the maximal level of progesterone was detected. The effects of the addition of LH to FSH-supplemented medium on the response of cumulus cells were affected by the suppression of the Ca 2+ -Protein kinase C pathway. Forskolin-induced p r o g e s t e r o n e p r o d u c t i o n w a s n o t a f f e c t e d b y suppression of the Ca 2+ -Protein kinase C pathway but was reduced by Protein kinase A inhibitor. These results showed that Ca 2+ -Protein kinase C pathway in cumulus cells stimulated by FSH, enhanced LH-induced progesterone production via a cAMP-Protein kinase A dependent pathway. [4][5][6]. When porcine COCs were cultured with LH, FSH, and progesterone synthesis inhibitor, almost complete inhibition of both progesterone production and GVBD was detected, and this inhibitory effect on GVBD was overcome by additional progesterone [6]. Therefore, progesterone secreted by cumulus cells is associated with meiotic maturation of porcine oocytes. Moreover, we also showed that the binding of progesterone to its receptor induced the disappearance of connexin-43 in cumulus cells, resulting in closing gap junctional communication in outer layers of cumulus cells [6,7]. In pigs, a significant positive correlation was seen between the proportion of GVBD oocytes and that of COCs exhibiting a loss of the gap junctional communication between the cumulus cells in outer layers [8,9]. Thus, the binding of progesterone to its receptor in cumulus cells exhibits GVBD in porcine oocytes, through closing gap junctional communication in outer layers of cumulus cells.The addition of adenylcyclase activator, forskolin, to the maturation medium has been reported to stimulate progesterone production in cumulus cells concomitantly with an increase in the cAMP level in the cells [10].

Expression of two progesterone receptor isoforms in cumulus cells and their roles during meiotic resumption of porcine oocytes

“…We have already shown that progesterone production in cumulus cells is significantly increased after 10 h of cultivation (Shimada et al 2002). In Fig.…”

Effects of adding luteinizing hormone to a medium containing follicle stimulating hormone on progesterone‐induced differentiation of cumulus cells during meiotic resumption of porcine oocytes

“…1980; Richards 1994). In porcine COC, we reported that the addition of LH to the FSH‐containing medium also produced a significant increase of progesterone production (Shimada et al . 2002a).…”