Characterization of purinergic P2X4 receptor channels expressed in anterior pituitary cells.
Anterior pituitary cells express cation-conducting P2X receptor channels (P2XRs), but their molecular identity, electrophysiological properties, cell-specific expression pattern, and physiological roles have been only partially characterized. In this study, we show by quantitative RT-PCR that mRNA transcripts for the P2X(4) subunit are the most abundant in rat anterior pituitary tissue and confirm the P2X(4)R protein expression by Western blot analysis. Single-cell patch-clamp recordings show that extracellular ATP induced an inward depolarizing current in a majority of thyrotropin-releasing hormone-responsive pituitary cells, which resembled the current profile generated by recombinant P2X(4)R. The channels were activated and desensitized in a dose-dependent manner and deactivated rapidly. Activation of these channels led to stimulation of electrical activity and promotion of voltage-gated and voltage-insensitive Ca(2+) influx. In the presence of ivermectin, a specific allosteric modulator of P2X(4)Rs, there was an approximately fourfold increase in the maximum amplitude of the ATP-induced inward current, accompanied by an increase in the sensitivity of receptors for ATP, slowed deactivation of receptors, and enhanced ATP-induced prolactin release. These results indicate that thyrotropin-releasing hormone-responsive cells, including lactotrophs, express homomeric and/or heteromeric P2X(4)Rs, which facilitate Ca(2+) influx and hormone secretion.
Zemkova
Hana
H
Section on Cellular Signaling, Program in Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510, USA.
Kucka
Marek
M
Li
Shuo
S
Gonzalez-Iglesias
Arturo E
AE
Tomic
Melanija
M
Stojilkovic
Stanko S
SS
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005260:Female; D015640:Ion Channel Gating / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D010902:Pituitary Gland / Q000166:cytology* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058848:Receptors, Purinergic P2X4
C548226:P2RX4 protein, human; C548228:P2rx4 protein, rat; D018048:Receptors, Purinergic P2; D058848:Receptors, Purinergic P2X4; D002118:Calcium