Signaling by extracellular nucleotides in anterior pituitary cells

Pituitary cells secrete ATP, which acts as an autocrine and/or paracrine extracellular messenger on two families of purinergic receptors: G-protein-coupled P2Y receptors (P2YRs) and ion-conducting P2X receptors (P2XRs). Lactotrophs and GH 3-immortalized cells express the P2Y 2R subtype. Several P2XR subtypes are expressed in pituitary cells. Gonadotrophs and somatotrophs express P2X 2aR and P2X 2bR, which occur as heteromeric channels. Lactotrophs and GH 3 cells express one or more ion-conducting subtypes from among P2X 3R, P2X 4R and P2X 7R in homomeric form. Thyrotrophs and corticotrophs also express P2XRs, but their identification requires further study. Pituitary cells express purinergic P1 receptors, which are activated by adenosine. The A 1R subtype of these receptors is expressed in melanotrophs and GH 3 cells. In this review, we briefly discuss the expression and coupling of A 1R and P2Y 2R, and focus on the expression and Ca 2+ signaling of P2XRs.