101. PGI2 opens potassium channels in retinal pericytes by cyclic AMP-stimulated, cross-activation of PKG
- Author
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Jason O. Burnette and Richard E. White
- Subjects
medicine.medical_specialty ,Patch-Clamp Techniques ,Potassium Channels ,Swine ,Prostacyclin ,Biology ,Retina ,Cellular and Molecular Neuroscience ,chemistry.chemical_compound ,Internal medicine ,Cyclic AMP ,Cyclic GMP-Dependent Protein Kinases ,medicine ,Animals ,Cells, Cultured ,Microscopy, Confocal ,Retinal ,Voltage-gated potassium channel ,KT5720 ,Epoprostenol ,Sensory Systems ,Calcium-activated potassium channel ,Potassium channel ,Cell biology ,Potassium channel activity ,Ophthalmology ,Endocrinology ,medicine.anatomical_structure ,chemistry ,cardiovascular system ,Pericyte ,Pericytes ,Ion Channel Gating ,Signal Transduction ,medicine.drug - Abstract
Pericytes exert an important influence on the control of retinal blood flow; however, little is known regarding the molecular basis of retinal pericyte excitability. The purpose of this study was to elucidate the signaling pathway of how prostacyclin (PGI2), an important endogenous regulator of retinal blood flow, stimulates potassium channel activity in retinal pericytes. Retinal pericytes were isolated from porcine eyeballs and plated on glass coverslips. Immunocytochemistry was performed to verify expression of the pericyte-specific ganglioside marker, 3G5 and smooth muscle alpha-actin. Activity of the large-conductance, voltage- and calcium-activated potassium (BKCa) channel was measured in retinal pericytes via single-channel patch-clamp, and channel identification was confirmed via biophysical and pharmacological characterization. PGI2 (10 microM) or beraprost (30 microM; more stable prostacyclin analog) dramatically stimulated the activity of BKCa channels isolated in cell-attached patches. These experiments strongly suggested that PGI2 stimulated BKCa channel activity via a diffusible second messenger. Similarly, chlorophenylthio (CPT)-cAMP (100 microM; membrane permeable cAMP derivative) induced a significant increase in BKCa channel activity; however, inhibition of the cAMP-dependent protein kinase (PKA) with 300 nM KT5720 could not reverse the stimulatory effect of either PGI2 or CPT-cAMP. In contrast, activation of BK(Ca) channels with either CPT-cAMP or PGI2 was abolished by 300 nM KT5823 (n=5, p
- Published
- 2006