CALCIUM STORES INVOLVED IN CALCIUM SIGNALING ACTIVATED BY PROGESTERONE IN HUMAN SPERM.

ARIAS RJ; DE BLAS GA; MAYORGA LS; SOSA CM

BUENOS AIRES

Congreso; Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2017

Calcium signaling is a key regulatory mechanism in sperm functions such as capacitation, motility, hyperactivation and acrosome reaction. Progesterone (Pg) produced by the oocyte cumulus has been associated with several processes of sperm physiology, since it directly activates plasma membrane Ca2+ channels. Pg open the channels triggering a rapid increase in intracellular calcium coming from the extracellular medium. It?s been described that some sperm organelles can operate as Ca2+ stores with functional importance in sperm function, like the acrosome vesicle, redundant nuclear envelope and mitochondria located in sperm?s middle piece. Our group in previous work have observed that Pg induces an intracellular calcium increase in media with different [Ca2+], yet is unclear if this calcium increase is due to calcium release from intracellular stores or other source. The aim of this study was to study the action of Pg on intracellular Ca2+ increase of human sperm incubated in media with different Ca2+ concentrations, also we analized how this increase is modified or altered by the presence or absence of different intracellular calcium modulators and mitochondrial inhibitors in order to elucidate which intracellular Ca2+ store is being activated by Pg. To meet this goal we perform dynamic tests on individual cells in real time and population using a spectrofluorometer. Capacitated human sperm were loaded with different fluorescent calcium probes -Fluo3-AM and Fura2-AM-, then incubated in medium containing different [Ca2+] and treated with progesterone in absence or presence of intracellular calcium modulators and mitochondrial modulators. We observed that media with different [Ca2+] generated increases of intracellular Ca2+ with differing kinetics and patterns in response to Pg. We also noticed that mitochondrial inhibitors and calcium modulators altered the Ca2+ patterns and kinetics previously observed. These results suggest that Pg can activate the exit of Ca2+ from intracellular stores in conditions of low extracellular [Ca2+].