Ensemble noise and current relaxation analysis of K+ current in single isolated salivary acinar cells from rat

The K+ channel in rat parotid gland acinar cells were investigated by ensemble current noise analysis in single isolated cells employing the giga-seal whole cell current recording mode. Sets of 20-40 identical de- and hyperpolarization voltage steps were applied and the resultant current records were processed by computer to obtain the mean and the variance of the current. The time-course of the mean current could be fitted by the sum of two exponentials, suggesting a 3-state model. The simplest plausible hypothesis is a model with one open and two closed states. Assuming this model, the relationship between the variance (sigma 2) and the mean current (I) could be fitted by the function sigma 2/I = i--I/N. The estimated single channel i/V-relations were similar to those taken from single channel current recordings, and the size of the population of channels per cell (N) was 76 +/- 26 (n = 12). The validity of the model was tested by a successful simulation of the time-course of the variance.