Characterization of purinergic P2X 4 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 t...
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Published in | American journal of physiology: endocrinology and metabolism Vol. 298; no. 3; pp. E644 - E651 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
01.03.2010
|
Online Access | Get full text |
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Summary: | 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. |
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ISSN: | 0193-1849 1522-1555 |
DOI: | 10.1152/ajpendo.00558.2009 |