Calcium waves in intact guinea pig gallbladder smooth muscle cells.
Intracellular Ca(2+) waves and spontaneous transient depolarizations were investigated in gallbladder smooth muscle (GBSM) whole mount preparations with intact mucosal layer [full thickness (FT)] by laser confocal imaging of intracellular Ca(2+) and voltage recordings with microelectrodes, respectively. Spontaneous Ca(2+) waves arose most often near the center, but sometimes from the extremities, of GBSM cells. They propagated regeneratively by Ca(2+)-induced Ca(2+) release involving inositol 1,4,5-trisphosphate [Ins(1,4,5)P(3)] receptors and were not affected by TTX and atropine (ATS). Spontaneous Ca(2+) waves and spontaneous transient depolarizations were more prevalent in FT than in isolated muscularis layer preparations and occurred with similar pattern in GBSM bundles. Ca(2+) waves were abolished by the Ins(1,4,5)P(3) receptor inhibitors 2-aminoethoxydiphenyl borate and xestospongin C and by caffeine and cyclopiazonic acid. These events were reduced by voltage-dependent calcium channels (VDCCs) inhibitors diltiazem and nifedipine, by PLC inhibitor U-73122, and by thapsigargin and ryanodine. ACh, CCK, and carbachol augmented Ca(2+) waves and induced Ca(2+) flashes. The actions of these agonists were inhibited by U-73122. These results indicate that in GBSM, discharge and propagation of Ca(2+) waves depend on sarco(endo)plasmic reticulum (SR) Ca(2+) release via Ins(1,4,5)P(3) receptors, PLC activity, Ca(2+) influx via VDCCs, and SR Ca(2+) concentration. Neurohormonal enhancement of GBSM excitability involves PLC-dependent augmentation and synchronization of SR Ca(2+) release via Ins(1,4,5)P(3) receptors. Ca(2+) waves likely reflect the activity of a fundamental unit of spontaneous activity and play an important role in the excitability of GBSM.
Balemba
Onesmo B
OB
D-406, Given Bldg., Dept. of Anatomy and Neurobiology, 89 Beaumont Ave., Univ. of Vermont, Burlington, VT 05405, USA.
Heppner
Thomas J
TJ
Bonev
Adrian D
AD
Nelson
Mark T
MT
Mawe
Gary M
GM
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D005704:Gallbladder / Q000166:cytology* / Q000378:metabolism*; D006168:Guinea Pigs; D053496:Inositol 1,4,5-Trisphosphate Receptors; D009130:Muscle, Smooth / Q000166:cytology* / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium