%0 Journal Article %A Drumm, Bernard T. %A Sergeant, Gerard P. %A Hollywood, Mark A. %A Thornbury, Keith T. %A Matsuda, Toshio T. %A Baba, Akemichi %A Harvey, Brian J. %A McHale, Noel G. %D 2019 %T The effect of high [K(+)]o on spontaneous Ca(2+) waves in freshly isolated interstitial cells of Cajal from the rabbit urethra. %U https://repository.rcsi.com/articles/journal_contribution/The_effect_of_high_K_o_on_spontaneous_Ca_2_waves_in_freshly_isolated_interstitial_cells_of_Cajal_from_the_rabbit_urethra_/10787255 %2 https://repository.rcsi.com/ndownloader/files/19300025 %K Calcium oscillations %K interstitial cell of Cajal %K smooth muscle %K sodium/calcium exchange %K Molecular Medicine %X

Interstitial cells of Cajal (ICC) act as putative pacemaker cells in the rabbit urethra. Pacemaker activity in ICC results from spontaneous global Ca(2+) waves that can be increased in frequency by raising external [K(+)]. The purpose of this study was to elucidate the mechanism of this response. Intracellular [Ca(2+)] was measured in fluo-4-loaded smooth muscle cells (SMCs) and ICC using a Nipkow spinning disk confocal microscope. Increasing [K(+)]o to 60 mmol/L caused an increase in [Ca(2+)]i accompanied by contraction in SMCs. Raising [K(+)]o did not cause contraction in ICC, but the frequency of firing of spontaneous calcium waves increased. Reducing [Ca(2+)]o to 0 mmol/L abolished the response in both cell types. Nifedipine of 1 μmol/L blocked the response of SMC to high [K(+)]o, but did not affect the increase in firing in ICC. This latter effect was blocked by 30 μmol/L NiCl2 but not by the T-type Ca(2+) channel blocker mibefradil (300 nmol/L). However, inhibition of Ca(2+) influx via reverse-mode sodium/calcium exchange (NCX) using either 1 μmol/L SEA0400 or 5 μmol/L KB-R7943 did block the effect of high [K(+)]o on ICC. These data suggest that high K(+) solution increases the frequency of calcium waves in ICC by increasing Ca(2+) influx through reverse-mode NCX.

%I Royal College of Surgeons in Ireland