Spontaneous calcium oscillations in urinary bladder smooth muscle cells.
Although spontaneous phasic activity of detrusor muscle plays an important role in urinary bladder function there is little information regarding myogenic [Ca(2+)](i) signals in this tissue. We have studied spontaneous, unstimulated [Ca(2+)](i) signals in fura-2 loaded detrusor cells isolated from newborn (10-13 days old) guinea-pig urinary bladder. In newborn guinea pigs 35% of studied muscle cells displayed spontaneous [Ca(2+)](i) oscillations with several kinetic patterns (from irregular to highly paced cycles). The oscillations were inhibited by external Ca(2+) removal, treatment with L- and T-type Ca(2+) channel blockers and by the hyperpolarizing drug pinacidil. Ca(2+) stores were necessary to maintain oscillations, as indicated by the inhibitory effects of thapsigargin, ryanodine and 2-APB. Oscillations were also inhibited by folimycin, an inhibitor of acidic Ca(2+) stores. Treatment with the selective inhibitors iberiotoxin and NPPB indicated that the oscillatory signal is also modulated by Ca(2+) -activated K(+) channels (inhibitory) and Ca(2+) -activated Cl(-) channels (stimulatory). Our results indicate that detrusor cells from newborn guinea-pigs develop spontaneous [Ca(2+)](i) oscillations due to Ca(2+) influx through T- and L-type Ca(2+) channels modulated by intracellular stores, including acidic pools. This activity could underlie the myogenic activity of urinary bladder during early stages of development.
Martin-Cano
F E
FE
Department of Physiology, Faculty of Veterinary Sciences and Nursing School, University of Extremadura, 10071 Caceres, Spain.
Gomez-Pinilla
P J
PJ
Pozo
M J
MJ
Camello
P J
PJ
D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D020746:Calcium Channels, L-Type / Q000502:physiology*; D020747:Calcium Channels, T-Type / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects; D005456:Fluorescent Dyes; D006168:Guinea Pigs; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors; D007700:Kinetics; D049990:Membrane Transport Modulators / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D020033:Protein Isoforms / Q000819:agonists / Q000037:antagonists & inhibitors; D019837:Ryanodine Receptor Calcium Release Channel; D001743:Urinary Bladder / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D014554:Urination / Q000502:physiology
D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D005456:Fluorescent Dyes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D049990:Membrane Transport Modulators; D020033:Protein Isoforms; D019837:Ryanodine Receptor Calcium Release Channel