Arachidonic acid triggers [Ca^2+]i increases in rat round spermatids by a likely GPR activation, ERK signalling & ER/acidic compartments Ca²⁺release

Arachidonic acid (AA), a compound secreted by Sertoli cells (SC) in a FSH-dependent manner, is able to induce the release of Ca²⁺from internal stores in round spermatids and pachytene spermatocytes. In this study, the possible site(s) of action of AA in round spermatids, the signalling pathways associated and the intracellular Ca²⁺stores targeted by AA-induced signalling were pharmacologically characterized by measuring intracellular Ca²⁺using fluorescent Ca²⁺probes. Our results suggest that AA acts by interacting with a fatty acid G protein coupled receptor, initiating a G protein signalling cascade that may involve PLA2 and ERK activation, which in turn opens intracellular ryanodine-sensitive channels as well as NAADP-sensitive channels in acidic intracellular Ca²⁺stores. The results presented here also suggest that AMPK and PKA modulate this AA-induced Ca²⁺release from intracellular Ca²⁺stores in round spermatids. We propose that unsaturated free fatty acid lipid signalling in the seminiferous tubule is a novel regulatory component of rat spermatogenesis.