A novel view of albumin-supported sperm capacitation: Role of Lipid Transfer Protein-I

S. E. Ravnik, J. J. Albers, C. H. Muller

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Objective: To determine if one mechanism of albumin-mediated support of human sperm capacitation is lipid (cholesterol) transfer activity and contamination of albumin with Lipid Transfer Protein-I (LTP-I). Design and Main Outcome Measures: Measure lipid transfer activity in various bovine and human albumin preparations; relate this activity to albumin-supported capacitation (measured by zona-free hamster oocyte sperm penetration assay) and acrosome reactions; and attempt to detect LTP-I in active albumins. Remove LTP-I from albumin which supports capacitation and reassess this support. Reconstitute capacitation support by addition of purified LTP-I. Setting and Subjects: Healthy sperm donors with normal semen analyses were recruited by the Reproductive Biology-Andrology Laboratory in a university medical center. Results: Albumin preparations that effectively support capacitation have high levels of lipid transfer activity and of LTP-I, a protein responsible for lipid transfer activity. Preparations with lower levels of capacitation support have less lipid transfer activity. Removal of LTP-I from supportive albumin significantly reduces the capacitation support, and this is restored by purified LTP-I. Progesterone concentrations in these preparations are negligible. Conclusions: The variable abilities of albumin preparations to support in vitro sperm capacitation are largely dependent on the presence of contaminating LTP-I. The cholesterol transfer activity of this protein, which is present in human serum and follicular fluid, may be one mechanism in the process of capacitation.

Original languageEnglish (US)
Pages (from-to)629-638
Number of pages10
JournalFertility and sterility
Issue number3
StatePublished - 1993


  • Human sperm capacitation
  • acrosome reaction
  • albumin
  • cholesterol
  • lipid transfer protein
  • serum
  • zona-free hamster oocyte sperm penetration assay

ASJC Scopus subject areas

  • Reproductive Medicine
  • Obstetrics and Gynecology


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