Affiliations: Department of Biophysics and Radiobiology, Federal
University of Pernambuco, Brazil | Department of Animal Morphology and Physiology,
Federal Rural University of Pernambuco, Brazil
Note: [] Corresponding author: Universidade Federal Rural de Pernambuco,
Departamento de Morfologia e Fisiologia Animal, R. Dom Manuel de Medeiros, s/n.
Dois Irmãos. Recife. PE. CEP: 52171-030, Brazil. Tel.: +81 33206395;
E-mail: ran.pe@terra.com.br
Abstract: The gating of ion channels has been modeled by assuming that the
transition between open and closed states is a memoryless process.
Nevertheless, analysis of records of unitary current events suggests that the
kinetic process presents short-term memory. We have previously proposed the
rescaled range analysis or R/S Hurst analysis as an efficient method to test
for the existence of long-term correlation (memory) in single ion channel. In
this paper, we investigate the effect of calcium on the memory of the single
calcium-activated potassium channel present in Leydig cells. The Hurst
coefficient (H; a parameter that predicts memory) was calculated for four
different calcium concentrations and presented the following values: 0.634
± 0.017 (n=8) for
10^{-6} M; 0.647 ± 0.001 (n=9) for 10^{-7} M; 0.614 ±
0.001 (n=6) for 10^{-8} M and
0.618 ± 0.001 (n=4) for
10^{-9} M. These values of H indicate that open- and
closed-dwell times are long-term correlated and that this memory does not
change in the presence of different calcium concentrations at a 5%
significance level. When the R/S Analysis was applied to the results obtained
from simulations of a markovian model (eleven states), it could not account for
the long-term correlation found in the experimental data.
Keywords: Long-term correlation, BK potassium channel, memory in single channel kinetics
