Extracellular adenosine triphosphate activates phospholipase C and mobilizes intracellular calcium in primary cultures of sheep anterior pituitary cells.

In primary cultures of sheep anterior pituitary cells extracellular ATP (ED50 0.4-0.8 microM) stimulated efflux of 45Ca2+ from a slow-turnover intracellular pool. ADP was also effective whereas AMP and adenosine were not. The ATP effect was not due to cell permeabilization as 100 microM ATP did not elicit efflux of 2-deoxy[3H]glucose metabolites. This 45Ca2+ mobilization may be mediated by inositol trisphosphate, since ATP (ED50 1 microM) stimulated inositol phosphate generation. These results demonstrate P2-purinoceptors in sheep anterior pituitary cells which are coupled to phospholipase C activation and intracellular Ca2+ mobilization, and raise the possibility of a regulatory role for extracellular ATP in the anterior pituitary.