MAYORGA Luis Segundo
congresos y reuniones científicas
Kinetics of the acrosomal exocytosis in human sperm
SOSA CM; ZANETTI, MN; ZOPPINO FCM; DE BLAS, G; MAYORGA, LS
Congreso; SAIB 2013; 2013
Our laboratory has shown that sperm and neuroendocrinal cells use similar molecular mechanism for secretion. However, we report here that the process is orders of magnitude slower. For these experiments, capacitated human sperm were stimulated with progesterone or with the calcium ionophore A23187 in the presence of a fluorescent lectin. The incorporation of the lectin into the acrosome -indicating fusion pore opening- was assessed in fixed or live cells by fluorescence microscopy or flow cytometry. Despite the slow kinetics of the exocytosis, the cytosolic calcium increased triggered by the stimuli occurred in seconds. To assess if acrosomal swelling, a process required for exocytosis, was responsible for the delay, we measured the kinetics of this process and observed that it required several minutes to be completed. We then tested the kinetics of fusion pore opening in sperm that had completed the swelling. For these experiments intraacrosomal calcium was depleted using the photosensitive calcium chelator NP-EGTA and sperm were stimulated with A23187. Exocytosis was completed when the chelator was photo-inactivated. Under these conditions the pores opened in seconds. These observations indicate that the acrosome reaction requires a preparation time, probably related to acrosomal swelling, whereas the fusion pore opening occurs with a fast kinetics.