P2 purinergic receptor-coupled signaling in the rabbit ciliary body epithelium.
OBJECTIVE
To identify and characterize P2 purinergic receptors and their signaling pathways in the epithelial cells of the rabbit ciliary body.


METHODS
Real-time fluorescence ratio imaging of the intact fura-2-loaded nonpigmented ciliary body epithelial (NPE) cells of rabbit were used to record changes in the intracellular free calcium concentration ([Ca(2+)](i)), in response to a number of purinergic agonists and antagonists. The effects of some of these drugs on the inositol phosphate (IP) levels in ciliary processes were also examined.


RESULTS
Adenosine diphosphate (ADP), adenosine triphosphate (ATP), and uridine triphosphate (UTP) dose dependently increased the [Ca(2+)](i) and IP levels. The [Ca(2+)](i) increases induced by ADP and UTP were distinguishable, both kinetically and pharmacologically. The effect of ADP on [Ca(2+)](i) was mimicked by a number of P2Y(1)-selective agonists, and was blocked by three P2Y(1)-receptor-specific antagonists. The [Ca(2+)](i) increases elicited by ADP (or its analogs) and UTP were additive.


CONCLUSIONS
Rabbit ciliary body epithelium possesses both P2Y(1) and P2Y(2) metabotropic purinergic receptor subtypes, which differentially use the IP(3)/Ca(2+) second-messenger pathway.
Farahbakhsh
Nasser A
NA
Department of Physiological Science, 3817 Life Sciences, University of California-Los Angeles, Los Angeles, CA 90095-1606, USA. nasserf@lifesci.ucla.edu
Cilluffo
Marianne C
MC
D000227:Adenine Nucleotides / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002924:Ciliary Body / Q000378:metabolism*; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011817:Rabbits; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058472:Receptors, Purinergic P2Y1; D058473:Receptors, Purinergic P2Y2; D015290:Second Messenger Systems / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*
D000227:Adenine Nucleotides; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D058473:Receptors, Purinergic P2Y2; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium; D016257:Fura-2