Expression of Purinergic Receptor Channels and Their Role in Calcium Signaling and Hormone Release in Pituitary Gonadotrophs

Abstract

] i oscillations by increasing the frequency, base line, and duration of Ca 2؉ spiking. In addition, ATP stimulated gonadotropin secretion and enhanced agonist-induced gonadotropin release. ATP was found to be secreted by pituitary cells during agonist stimulation and was promptly degraded by ectonucleotidase to adenosine. These observations indicate that ATP represents a paracrine/autocrine factor in the regulation of Ca 2؉ signaling and secretion in gonadotrophs, and that these actions are mediated by P 2 receptor channels.

Expression of P2Y receptors in the rat anterior pituitary

“…Such basal ATP release was enhanced in cells simulated by ARL67156, an inhibitor of ectonucleotidases [13]. GnRH-induced stimulation of gonadotropin release was accompanied by elevation in basal ATP release, raising the possibility that ATP is stored in the secretory vesicles of these cells [2]. This is consistent with an earlier study showing calcium dependence of ATP release [23].…”

“…Using the technique of single-cell calcium measurement, the initial characterization of purinoceptors in anterior pituitary cells were identified [2][3][4][5][6]. These experiments revealed that functional P2X receptors are operative in all secretory cell types.…”

“…There are two subgroups of G proteins which P2Y receptors are coupled with, namely Gq and Gi. P2Y 1 , P2Y 2 , P2Y 4 and P2Y 6 receptors are linked to activation of phospholipase C (PLC), inositol lipid signaling and the mobilization of intracellular Ca 2+ , P2Y 12, P2Y 13 and P2Y 14 receptors are coupled with Gi protein 1 − S100 + cells/total number of S100 + cells×100 2 + S100 + /total number of P2Y 2 + cells×100; p8=number of P2Y 2 + S100 − /total number of P2Y 2 + cells×100; p9= number of FSH + P2Y 2 − /total number of TSH + cells×100; p10= number of PRL + P2Y 2 − /total number of PRL + cells×100; p11=number of P2Y 2 − TSH + cells/total number of TSH + cells×100; p12=number of P2Y 2 − S100 + /total number of S100 + cells×100 Table 2 Coexistence between P2Y receptors and pituitary hormones or S100 P2Y ACTH FSH GH PRL TSH S100…”

“…With molecular biology techniques, P2X 2 , P2X 3 , P2X 4 , and P2X 7 mRNA transcripts were detected in a mixed population of anterior pituitary cells. Lactotrophs and immortalized GH3 pituitary cells expressed transcripts for P2X 3 , P2X 4 , and P2X 7 subunits, somatotrophs expressed P2X 2 receptor, and thyrotrophs and corticotrophs also express P2X receptors [7] Single-cell patch-clamp analysis in gonadotrophs from embryonic, neonatal, and adult rats revealed that P2X 2 receptors are operative and involved in release of luteinizing hormone (LH) and regulation of gonadotrophinreleasing hormone (GnRH) controlled electrical activity and secretion [8]. Lactotrophs express P2X 4 receptors, which facilitate Ca 2+ influx and hormone secretion [9].…”

“…In this study, we used single-labeling and doublelabeling immunofluorescence, in situ hybridization and Western blot analyses to study the distribution patterns of P2Y 1 , P2Y 2 P2Y 4 , P2Y 6 , P2Y 12 , and P2Y 13 receptors in anterior pituitary cells of rat and found that gonadotrophs and thyrotrophs express P2Y 1 and P2Y 4 receptors, lactotrophs and folliculo-stellate cells express P2Y 2 , and macrophages express P2Y 6 .…”