Purinergic regulation of intracellular Ca2+ concentration of rat pituitary folliculo-stellate cells in primary culture

Pituitary folliculo-stellate cells (FSCs) are glia-like cells in the anterior pituitary and are believed to modulate the activity of the pituitary endocrine cells. However, little is known what regulates the activity of FSCs. We hypothesized that ATP could act on FSCs, because ATP is coreleased with pituitary hormones from endocrine cells. To test this possibility, we examined the effect of ATP by measuring intracellular Ca2+ concentration [Ca2+](i) of FSCs in primary culture. Both ATP and UTP increased the [Ca2+](i) in a concentration-dependent manner in a range between 0.1 muM and 10 muM. The response was completely suppressed by thapsigargin, an inhibitior of endoplasmic reticulum Ca2+-ATPase, and was significantly suppressed by U-73122, an inhibitor of phospholipase C. The response was also suppressed by caffeine, a blocker of IP3 receptor, whereas that was not suppressed by ryanodine, an antagonist of ryanodine receptor. These results indicate that ATP increases [Ca2+](i) of FSCs by activating phospholipase C via P2Y purinergic receptor and suggest that ATP would be one of paracrine factors to FSCs in the anterior pituitary.