Spark frequency

Bonev AD, Jaggar JH, Rubart M, Nelson MT 1997 Activators of protein kinase C decrease Ca2+ spark frequency in smooth muscle cells from cerebral arteries. Am J Physiol Cell Physiol... 

Nelson It could. We could try to load the SR. For example, we have used the phospholamban knockout mouse where it appears that the SR Ca2+ load increases (Wellman et al 2001). The spark frequency increases as the load increases. At the moment we have not observed any communication from the SR to the SK channels. 

Nelson I would like to return to what David Eisner mentioned about the plasma membrane determining the steady-state free Ca2+, and what Rick Paul said about sparks and long-conductance Ca2+-dependent K+ (BK) channels. We have looked at cerebral arteries from PLB knockout mice. The spark frequency and the associated transient BK current frequency are elevated by about a factor of three. SR load goes up, the membrane potential hyperpolarizes and the artery relaxes. It would be useful to measure membrane potential under all the conditions as well as determine the voltage dependence of tone, to make sure that your manipulations are not simply changing the membrane potential. 

Volkers M, Loughrey CM, Macquaide N, Remppis A, de George B, Wegner FV, Friedrich O, Fink RH, Koch WJ, Smith GL, Most P. 2006. S100A1 decreases calcium spark frequency and alters their spatial characteristics in permeabilized adult ventricular cardiomyocytes. Cell Calcium. 

The frequency and amplitude of calcium sparks are modulated by SR calcium load, protein kinase C (PKC) and cyclic nucleotides/cyclic nucleotide-dependent protein kinases (Bonev et al. 1997 Porter et al. 1997). Calcium spark frequency decreases following activation of PKC (Bonev et al. 1997). This effect appears to be mediated by a direct action of PKC on... 

Io = Uo- Ub) /( t/oVWO The spark frequency within the spark train is ... 

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