Email updates

Keep up to date with the latest news and content from BMC Neuroscience and BioMed Central.

Open Access Research article

Selective stimulation of catecholamine release from bovine adrenal chromaffin cells by an ionotropic purinergic receptor sensitive to 2-methylthio ATP

Ângelo R Tomé12, Enrique Castro3, Rosa M Santos12 and Luís M Rosário12*

Author Affiliations

1 Center for Neurosciences and Cell Biology, University of Coimbra, Coimbra, Portugal

2 Department of Biochemistry, Faculty of Sciences and Technology, University of Coimbra, P.O. Box 3126, 3001-401 Coimbra, Portugal

3 Department of Biochemistry, Molecular Biology and Physiology, Faculty of Medicine and Health Sciences, University of Las Palmas de Gran Canaria, Las Palmas, Spain

For all author emails, please log on.

BMC Neuroscience 2007, 8:41  doi:10.1186/1471-2202-8-41

Published: 20 June 2007

Abstract

Background

2-Methylthioadenosine 5'-triphosphate (2-MeSATP), formerly regarded as a specific P2Y (metabotropic) purinergic receptor agonist, stimulates Ca2+ influx and evokes catecholamine release from adrenal chromaffin cells. These cells express P2Y and P2X (ionotropic) purinoceptors, with the latter providing an important Ca2+ influx pathway. Using single cell calcium imaging techniques, we have determined whether 2-MeSATP might be a specific P2X receptor agonist in bovine chromaffin cells and assessed the relative role of P2X and P2Y receptors on catecholamine secretion from these cells.

Results

ATP raised the [Ca2+]i in ~50% of the cells. Removing extracellular Ca2+ suppressed the [Ca2+]i-raising ability of 2-MeSATP, observed in ~40% of the ATP-sensitive cells. This indicates that 2-MeSATP behaves as a specific ionotropic purinoceptor agonist in bovine chromaffin cells. The 2-MeSATP-induced [Ca2+]i-rises were suppressed by PPADS. UTP raised the [Ca2+]i in ~40% of the ATP-sensitive cells, indicating that these expressed Ca2+-mobilizing P2Y receptors. UTP-sensitive receptors may not be the only P2Y receptors present, as suggested by the observation that ~20% of the ATP-sensitive pool did not respond to either 2-MeSATP or UTP. The average sizes of the ATP- and 2-MeSATP-evoked [Ca2+]i responses were identical in UTP-insensitive cells. 2-MeSATP stimulated Ca2+ influx and evoked catecholamine release, whereas UTP elicited Ca2+ release from intracellular stores but did not evoke secretion. 2-MeSATP-induced secretion was strongly inhibited by Cd2+ and suppressed by extracellular Ca2+ or Na+ removal. TTX inhibited 2-MeSATP-evoked secretion by ~20%.

Conclusion

2-MeSATP is a specific P2X purinoceptor agonist and a potent secretagogue in bovine chromaffin cells. Activation of 2-MeSATP-sensitive receptors stimulates Ca2+ influx mainly via voltage-sensitive Ca2+ channels. For the most part, these are activated by the depolarization brought about by Na+ influx across P2X receptor pores.