Electrophysiological and immunocytochemical evidence for P2X purinergic receptors in pancreatic beta cells.
OBJECTIVE
Glucose-induced insulin secretion from pancreatic beta cells is modulated by several hormones and transmitters, namely adenosine triphosphate (ATP) via purinergic receptors. Although P2Y receptors are well documented in beta cells, the presence of P2X receptors remains elusive. We present the first electrophysiological evidence for the presence of P2X receptors in single beta cells of different species.


METHODS
Ionic currents were recorded from voltage-clamped beta cells near their resting potential using the perforated (nystatin) whole-cell patch-clamp configuration. Receptors were detected by immunocytochemistry.


RESULTS
When bathed in substimulatory (2 mM) glucose, mouse beta cells, isolated from islets displaying immunochemical colocalization of P2X1 or P2X3 receptors and insulin, developed large (approximately 250 pA/pF), rapidly activating, and then biexponentially decaying (tau1, approximately 20 milliseconds/tau2, approximately 1 second) inward currents on exposure to micromolar concentrations of ATP and alpha,beta-methylene ATP. The ATP also evoked inward currents (100-300 pA/pF) from porcine and human beta cells, albeit with a slower and more complex inactivation pattern.


CONCLUSIONS
The ATP-gated ion channels are present in pancreatic beta cells from different species. Specifically, mouse beta cells express rapidly desensitizing P2X1 and P2X3 receptors. Paracrine or neural activation of these receptors may contribute to the initial outburst of glucose- or acetylcholine-evoked insulin release, thus enhancing the islet secretory response.
Silva
Amélia M
AM
Center for Technological, Environmental and Life Studies, University of Trás-os-Montes e Alto Douro, Vila Real, Portugal.
Rodrigues
Ricardo J
RJ
Tomé
Angelo R
AR
Cunha
Rodrigo A
RA
Misler
Stanley
S
Rosário
Luís M
LM
Santos
Rosa M
RM
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D004594:Electrophysiology; D005260:Female; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects; D051379:Mice; D018408:Patch-Clamp Techniques; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058469:Receptors, Purinergic P2X; D058477:Receptors, Purinergic P2X3; D013552:Swine
D007328:Insulin; C546407:P2RX3 protein, human; C546409:P2rx3 protein, mouse; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058477:Receptors, Purinergic P2X3; D000255:Adenosine Triphosphate; D005947:Glucose; C002630:alpha,beta-methyleneadenosine 5'-triphosphate