Lipid Transfer Activity in Human Follicular Fluid: Relation to Human Sperm Capacitation

S. E. Ravnik, P. W. Zarutskie, C. H. Muller

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


A potentially important event during sperm capacitation is the loss of sperm membrane cholesterol. Although the exact mechanisms mediating this loss are not known, albumin and high density lipoprotein have been proposed as lipid acceptors. The authors propose that lipid transfer may be involved in capacitation as a specific mediator in the sequence of events leading to sperm membrane cholesterol loss. We present the first direct evidence of lipid transfer activity (LTA) in human follicular fluid (HFF). The redistribution of 14C‐cholesteryl ester among human plasma lipoproteins was used as a measure of LTA (% Transfer [%T]). The HFF was fractionated by S‐300 gel filtration chromatography and assayed for LTA. Three peaks of activity were consistently eluted from the column. Each peak of LTA also stimulated human sperm to penetrate zona‐free hamster oocytes after short capacitating incubations. The peak with highest LTA (12.75 ± 1.11 %T) with an Mr approximately 68,000, gave the greatest stimulation (penetration index, PI: 3.34 ± 0.96 fold increase above control, n = 4). The HFF also showed a significant dose response for both LTA and PI, whereas bovine serum albumin did not. These results demonstrate the existence of LTA in HFF and suggest that a specific lipid transfer protein may have a role in human sperm capacitation or acrosome reaction. 1990 American Society of Andrology

Original languageEnglish (US)
Pages (from-to)216-226
Number of pages11
JournalJournal of Andrology
Issue number3
StatePublished - 1990


  • acrosome reaction
  • capacitation
  • cholesteryl ester
  • follicular fluid
  • human
  • lipid transfer
  • lipids
  • sperm
  • sperm penetration assay

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Reproductive Medicine
  • Endocrinology
  • Urology


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