Signaling by extracellular nucleotides in anterior pituitary cells

Pituitary cells secrete ATP, which acts as an autocrine and/or paracrine ex tracellular messenger on two families of purinergic receptors: G-protein-co upled P2Y receptors (P2YRs) and ion-conducting P2X receptors (P2XRs). Lacto trophs and GH(3)-immortalized cells express the P2Y(2)R subtype. Several P2 XR subtypes are expressed in pituitary cells. Gonadotrophs and somatotrophs express P2X(2a)R and P2X(2b)R, which occur as heteromeric channels. Lactot rophs and GH, cells express one or more ion-conducting subtypes from among P2X(3)R, P2X(4)R and P2X(7)R in homomeric form. Thyrotrophs and corticotrop hs also express P2XRs, but their identification requires further study. Pit uitary cells express purinergic pi receptors, which are activated by adenos ine. The A(1)R subtype of these receptors is expressed in melanotrophs and GH, cells. In this review, we briefly discuss the expression and coupling o f A(1)R and P2Y(2)R, and focus on the expression and Ca2+ signaling of P2XR s.