VERY-LONG-CHAIN (C28-C32) POLYENOIC FATTY ACIDS MOBILIZE INTRACELLULAR CALCIUM IN ROUND SPERMATIDS

SANTIAGO VALTIERRA, F.X.; PEÑALVA, D.A.; LUQUEZ, J.M.; AVELDAÑO, M.I.; REYES, J.G.; ORESTI, G.M.

Congreso; XXXI Reunión Virtual Sociedad Chilena de Reproducción y Desarrollo; 2020

Sociedad Chilena de Reproducción y Desarrollo

Rat spermatogenic cell membranes contain sphingolipids (SL) with very-long-chain (C28-32) polyunsaturated fatty acids (VLCPUFA) in non-hydroxylated (n-V) and 2-hydroxylated (h-V) forms. In addition to their structural role as components of germ and sperm cell membrane SL, and as precursors in the biosynthesis of such SL, possible biological roles of these fatty acids in their free form (FFA) in the physiology of these cells are unknown. The aim of this study was to explore the ability of three n-V FFAs, n-28:4, n-30:5, and n-32:5, and their h-V counterparts, to modify calcium homeostasis in rat spermatogenic cells. We prepared free n-V and h-V FFA from the sphingomyelin of germ cells (natural proportions, 79:18:3 and 38:54:8, respectively) and added each to spermatocytes and spermatids. At 8 µM concentration, the combined n-V, were able to intensely increase the intracellular calcium ([Ca2+]i) in spermatids, while the combined h-V did not. Then we separated the components of each mixture by HPLC to study the effect of each FFA individually, finding that n-32:5 was mostly responsible for the increased [Ca2+]i, followed by n-30:5, while h-32:5 only marginally increased it. In addition to fatty acid-specific, the response was dose-dependent. Ceramides containing the same fatty acids had no effect. In addition, the rates of [Ca2+]i increase were independent of the presence of extracellular calcium. Pretreatment with the endoplasmic reticulum calcium pump inhibitor thapsigargin prevented the effect of n-32:5, suggesting that it is mediated by a member of the family of the sarcoplasmic or endoplasmic reticulum Ca-ATPases (SERCA). Our results revealed a biological activity of VLCPUFA that deserves further studies to establish its possible functional roles in male reproductive physiology.