Forskolin and methylxanthines block the increase in intracellular pH during meiosis in Xenopus laevis oocytes.

Xenopus oocytes, arrested in late prophase of the meiotic cell cycle, undergo nuclear membrane breakdown (Germinal Vesicle Breakdown, GVBD) in response to progesterone stimulation. During this prophase/M-phase transition the oocytes undergo an increase in their intracellular pH (pHi) from 7.3 to 7.7 in response to the steroid. This increase in pHi appears to be due to the activation of Na+/H+ antiporters in the oocyte plasma membrane. Several studies have shown that the pathway leading to GVBD is blocked by forskolin or methylxanthines which elevate cAMP levels within the oocyte. We have found that these same compounds also blocked the up-regulation of the Na+/H+ exchangers during oocyte meiotic maturation.