Article date: August 2000
By: Hae Sook Chung, Kyu Sang Park, Seung Kyu Cha, In Deok Kong, Joong Woo Lee in Volume 130, Issue 8, pages 1843-1852
Extracellular ATP is a neurotransmitter and mediates a variety of responses. In the endocrine system, there are data suggesting a physiological role for ATP in Ca2+ signalling and hormone secretion. However, the ATP receptor subtype involved has not been clearly elucidated in GH3 cells, a rat anterior pituitary cell line.
BzATP‐ and ATP‐induced [Ca2+]i responses had EC50 values of 18 and 651 μM, respectively. The maximal response to ATP was only 59±8% of that for BzATP. The BzATP‐induced [Ca2+]i increase was dependent upon the extracellular Ca2+ concentration. Preincubation with oxidized ATP (oATP) nearly abolished the ATP‐ and BzATP‐induced [Ca2+]i increases.
Both BzATP and ATP induced depolarization in GH3 cells, with EC50 values of 31 μM and 1 mM, respectively. The maximal depolarization to BzATP and ATP were 152±21 and 146±16% of that elicited by 30 mM KCl.
The rank order of agonist potency for [Ca2+]i and depolarization responses was BzATP ≫ ATP >2‐MeSATP and purine derivatives such as ADP, AMP, adenosine were ineffective. Neither UTP nor α, β‐methylene ATP showed any effect.
In low‐divalent conditions BzATP evoked non‐desensitizing inward currents, which were reversed at ∼0 mV. This nonselective cationic conductance was increased by repeated applications of BzATP and the cells became very permeable to NMDG. Longer applications (30 min) of BzATP stimulated ethidium bromide influx in low divalent conditions, suggesting increased permeability to larger molecules. We also identified the existence of P2X7 mRNA on GH3 cells by using reverse transcriptase (RT)‐polymerase chain reaction (PCR).
These results suggest that the GH3 cells have an endogenous P2X7 receptor and purinergic stimulation may play a potential role in neuroendocrine modulation on these cells.
Extracellular ATP is a neurotransmitter and mediates a variety of responses. In the endocrine system, there are data suggesting a physiological role for ATP in Ca2+ signalling and hormone secretion. However, the ATP receptor subtype involved has not been clearly elucidated in GH3 cells, a rat anterior pituitary cell line.
BzATP‐ and ATP‐induced [Ca2+]i responses had EC50 values of 18 and 651 μM, respectively. The maximal response to ATP was only 59±8% of that for BzATP. The BzATP‐induced [Ca2+]i increase was dependent upon the extracellular Ca2+ concentration. Preincubation with oxidized ATP (oATP) nearly abolished the ATP‐ and BzATP‐induced [Ca2+]i increases.
Both BzATP and ATP induced depolarization in GH3 cells, with EC50 values of 31 μM and 1 mM, respectively. The maximal depolarization to BzATP and ATP were 152±21 and 146±16% of that elicited by 30 mM KCl.
The rank order of agonist potency for [Ca2+]i and depolarization responses was BzATP ≫ ATP >2‐MeSATP and purine derivatives such as ADP, AMP, adenosine were ineffective. Neither UTP nor α, β‐methylene ATP showed any effect.
In low‐divalent conditions BzATP evoked non‐desensitizing inward currents, which were reversed at ∼0 mV. This nonselective cationic conductance was increased by repeated applications of BzATP and the cells became very permeable to NMDG. Longer applications (30 min) of BzATP stimulated ethidium bromide influx in low divalent conditions, suggesting increased permeability to larger molecules. We also identified the existence of P2X7 mRNA on GH3 cells by using reverse transcriptase (RT)‐polymerase chain reaction (PCR).
These results suggest that the GH3 cells have an endogenous P2X7 receptor and purinergic stimulation may play a potential role in neuroendocrine modulation on these cells.
British Journal of Pharmacology (2000) 130, 1843–1852; doi:10.1038/sj.bjp.0703253
DOI: 10.1038/sj.bjp.0703253
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