Calcium requirements for human sperm function in vitro

MARIN BRIGGILER, CLARA I; GONZALEZ ECHEVERRIA, FERNANDA; BUFFONE, MARIANO; CALAMERA, JUAN; TEZON, JORGE G; VAZQUEZ-LEVIN, MÓNICA

FERTILITY AND STERILITY

Año: 2003 vol. 79 p. 1396 - 1403

0015-0282

Abstract Objective: To determine extracellular calcium (Ca2+) requirements for the maintenance of human sperm function in vitro. Design: Prospective study. Setting: Basic research laboratory. Subject(s): Fresh semen samples obtained from normozoospermic volunteers. Follicular fluid (hFF) and oocytes collected from women undergoing IVF-ET. Intervention(s): Spermatozoa were incubated for up to 18 h in media containing different CaCl2 concentrations (maximum 2.5 mM, control). Main Outcome Measure(s): Protein tyrosine phosphorylation patterns, development of hyperactivated motility, induction of the acrosome reaction (AR) in response to hFF, and sperm interaction with homologous zona pellucida (ZP). Result(s): Cells maintained for 18 h in medium containing at least 0.1 mM-Ca2+ were able to undergo the AR when exposed to hFF in the presence of 2.5 mM-Ca2+. Calcium concentrations ³ 0.22 mM were sufficient to reach protein tyrosine phosphorylation levels and hyperactivated motility values similar to controls. Higher Ca2+ concentrations (³ 0.58 mM) were required to produce maximum hFF-induced AR in previously capacitated cells and to obtain an adequate sperm-ZP binding. Conclusion(s): Different steps of the fertilization process have distinctive Ca2+ requirements. While 0.22 mM-Ca2+ is sufficient for the development of some capacitation-related events, hFF-induced AR and sperm-ZP interaction require 0.58 mM of this cation.