title: The role of cAMP dependent protein kinase in modulating spontaneous intracellular Ca²⁺ waves in interstitial cells of Cajal from the rabbit urethra.
abstract: Interstitial cells of Cajal (ICC) serve as electrical pacemakers in the rabbit urethra. Pacemaking activity in ICC results from spontaneous intracellular Ca(2+) waves that rely on Ca(2+) release from endoplasmic reticulum (ER) stores. The purpose of this study was to investigate if the action of protein kinase A (PKA) affected the generation of Ca(2+) waves in ICC. Intracellular [Ca(2+)] was measured in fluo-4 loaded ICC, freshly isolated from the rabbit urethra using a Nipkow spinning disc confocal microscope. Application of the PKA inhibitor H-89 (10 μM) significantly inhibited the generation of spontaneous Ca(2+) waves in ICC and this was associated with a significant decrease in the ER Ca(2+) load, measured with 10mM caffeine responses. Ca(2+) waves could be rescued in the presence of H-89 by stimulating ryanodine receptors (RyRs) with 1mM caffeine but not by activation of inositol 1,4,5 tri-phosphate receptors (IP3Rs) with 10 μM phenylephrine. Increasing intracellular PKA with the cAMP agonists forskolin and 8-bromo-cAMP failed to yield an increase in Ca(2+) wave activity. We conclude that PKA may be maximally active under basal conditions in ICC and that inhibition of PKA with H-89 leads to a decreased ER Ca(2+) load sufficient to inactivate IP3Rs but not RyRs.
authors: Smooth Muscle Research Centre, Dundalk Institute of Technology, Dublin Road, Co. Louth, Ireland; Molecular Medicine Laboratories, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Co. Dublin, Ireland. Electronic address: bdrumm@medicine.nevada.edu.
authors: Bernard T
authors: BT
authors: Drumm
authors: Smooth Muscle Research Centre, Dundalk Institute of Technology, Dublin Road, Co. Louth, Ireland.
authors: Gerard P
authors: GP
authors: Sergeant
authors: Smooth Muscle Research Centre, Dundalk Institute of Technology, Dublin Road, Co. Louth, Ireland.
authors: Mark A
authors: MA
authors: Hollywood
authors: Smooth Muscle Research Centre, Dundalk Institute of Technology, Dublin Road, Co. Louth, Ireland.
authors: Keith D
authors: KD
authors: Thornbury
authors: Smooth Muscle Research Centre, Dundalk Institute of Technology, Dublin Road, Co. Louth, Ireland.
authors: Noel G
authors: NG
authors: McHale
authors: Molecular Medicine Laboratories, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Co. Dublin, Ireland.
authors: Brian J
authors: BJ
authors: Harvey
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D056885:Interstitial Cells of Cajal / Q000166:cytology / Q000378:metabolism*; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D010656:Phenylephrine / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D014521:Urethra / Q000166:cytology / Q000378:metabolism*
chemical_list: D000697:Central Nervous System Stimulants; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007546:Isoquinolines; D047428:Protein Kinase Inhibitors; D019837:Ryanodine Receptor Calcium Release Channel; D013449:Sulfonamides; D010656:Phenylephrine; D002110:Caffeine; D015544:Inositol 1,4,5-Trisphosphate; D017868:Cyclic AMP-Dependent Protein Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium
keywords: Ca(2+) waves; ICC; PKA; Urethra