A new way for the analysis of the exocytosis

Exocytosis is the most common way for cells to secrete substances. This is a wide distributed phenomenon that involves all cell types and all animal species from yeast to human. Catecholamine (CA) release from adrenal chromaffin cells occurs by the exocytosis of secretory vesicles also called chromaffin granules. Individual secretory events can be easily monitored by the use of carbon fibers encased in glass microelectrodes. Catecholamines oxidized at the electrode tip produce a transient electrical current wave called secretory spike. The typical secretory spike consists in a sharp elevation of current followed by a rapid exponential decrease to the basal level. A 35-50% of the spikes showed a pre-spike wave called "foot" which represents the CA release through the fusion pore. The time course of secretory spikes observed is altered by extracellular phenomena's like diffusion. It has been suggested that amperometric spikes can be described by the convolution of a Gaussian with a decreasing exponential. The exponential function is partially governed by the diffusion of the secreted substances towards the electrode. In this article a method to deconvolve both functions is proposed. This mathematical approach allows the observation of the original secretory profile--the Gaussian--without the distortion caused by the diffusional broadening of catecholamines.