Phospholipase C-β and ovarian sex steroids in pig granulosa cells

✍ Scribed by Michèle Lieberherr; Brigitte Grosse; Véronique Machelon

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 152 KB
• Volume: 74
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/(sici)1097-4644(19990701)74:1<50::aid-jcb6>3.0.co;2-i

✦ Synopsis

We compared the membrane effects of estradiol, progesterone, and androstenedione in a single experimental model, the ovarian granulosa cells collected from immature Large White sows. We measured changes in cytosolic free calcium concentration ([Ca 2ϩ ]i) in confluent Fura-2 loaded cells. We used pharmacological tools and polyclonal phospholipase C-␤ (PLC-␤) antibodies. Each steroid (0.1 pM to 1 nM) transiently increased intracellular calcium concentration ([Ca 2ϩ ]i) within 5 sec. They mobilized Ca 2ϩ from the endoplasmic reticulum as shown by using two phospholipase C inhibitors, neomycin and U-73122. Ca 2ϩ mobilization involved PLC-␤1 for progesterone, PLC-␤2 for estradiol and PLC-␤4 for androstenedione. A pertussis toxin-insensitive G protein was involved in the effects of progesterone on Ca 2ϩ mobilization whereas estradiol and androstenedione effects were mediated via a pertussis toxin-sensitive G-protein. Ca 2ϩ influx from the extracellular milieu was involved in the increase in [Ca 2ϩ ]i induced by progesterone and estradiol, but not by androstenedione. Influx of Ca 2ϩ was independent of Ca 2ϩ mobilization from calcium stores, and it was suggested that L-type Ca 2ϩ channels for estradiol and T-type Ca 2ϩ channels for progesterone were involved. The three steroids had no effect on cAMP. Rapid effects of progesterone, estradiol, and androstenedione involved a direct action on cell membrane elements such as PLC-␤, G-proteins, and calcium channels, and these mechanisms were hormone-specific.