Spontaneous calcium oscillations in urinary bladder smooth muscle cells

• Published in: Journal of physiology and pharmacology : an official journal of the Polish Physiological Society Vol. 60; no. 4; p. 93
• Main Authors: Martin-Cano, F E, Gomez-Pinilla, P J, Pozo, M J, Camello, P J
• Format: Journal Article
• Language: English
• Published: Poland 01.12.2009
• Subjects: Aging; Animals; Animals, Newborn; Calcium Channels, L-Type - physiology; Calcium Channels, T-Type - physiology; Calcium Signaling - drug effects; Fluorescent Dyes; Guinea Pigs; Inositol 1,4,5-Trisphosphate Receptors - antagonists & inhibitors; Kinetics; Membrane Transport Modulators - pharmacology; Microscopy, Fluorescence; Myocytes, Smooth Muscle - drug effects; Myocytes, Smooth Muscle - metabolism; Protein Isoforms - agonists; Protein Isoforms - antagonists & inhibitors; Ryanodine Receptor Calcium Release Channel; Urinary Bladder - drug effects; Urinary Bladder - growth & development; Urinary Bladder - metabolism; Urination - physiology
• ISSN: 1899-1505

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.