Monoclonal antibodies increase intracellular Ca2+ in sea urchin spermatozoa

J. S. Trimmer, R. W. Schackmann, V. D. Vacquier

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Changes in intracellular Ca2+ ([Ca2+](i)) of sea urchin (Strongylocentrotus purpuratus) spermatozoa were measured using the fluorescent Ca2+ indicators fura-2 and indo-1. The intracellular pH (pH(i)) of sperm was also determined. The fucose sulfate-rich glycoconjugate component of egg jelly induced increases in [Ca2+](i) and pH(i) in sperm and induced the acrosome reaction. Monoclonal antibodies (mAbs) to external domains of a 210-kDa glycoprotein of the sperm plasma membrane induced a 23-fold increase in [Ca2+](i) (vs. 9-fold for fucose sulfate-rich glycoconjugate), but the mAbs did not cause the pH(i) to increase and did not induce the acrosome reaction. When the mAb treatment which induced an increase in [Ca2+](i) was combined with an NH4Cl treatment, which increased the pH(i), the acrosome reaction was induced. mAb-induced increases in [Ca2+](i) were dependent on millimolar concentrations of extracellular Ca2+ and were reversed by placing sperm in Ca2+-free seawater or by chelating Ca2+ with EGTA. The mAb-induced [Ca2+](i) increase was sensitive to the pH of the seawater, although mAb binding was not. The data show that increased [Ca2+](i) and pH(i) are necessary for induction of the acrosome reaction and suggest that the 210 kDa-protein may play a role in regulating Ca2+ entry into the spermatozoan. These mAbs make it possible to separate the increase in [Ca2+](i) from the increase in pH(i) and may be useful in the elucidation of the regulatory role of Ca2+ in sperm physiology.

Original languageEnglish (US)
Pages (from-to)9055-9059
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number23
StatePublished - 1986

ASJC Scopus subject areas

  • General
  • Genetics


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