Cholesterol efflux from bovine sperm. I. Induction of the acrosome reaction with lysophosphatidylcholine after reducing sperm cholesterol

Wiley - Tập 20 Số 2 - Trang 145-157 - 1988
Eduardo Ehrenwald1, John E. Parks2, R.H. Foote3
1Department of Animal Science, Cornell University, Ithaca, New York 14853
2201 Morrison Hall, Cornell University, Ithaca, NY 14853
3Department of Animal Science Cornell University Ithaca, New York

Tóm tắt

AbstractMethods were developed to quantitatively reduce the cholesterol (Chol)/phospholipid (PL) ratio of bovine sperm and to determine the effectiveness of this treatment in capacitating sperm. Washed sperm (2 × 108) were incubated in 1.0 ml of modified Tyrode's solution (TS) containing unilamellar liposomes of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and [14C]‐Chol (35:35:30 molar ratio, 300 nmol total PL). [3H]‐triolein was included as a nonexchangable marker. After 90 min at 39°C, a 13% net exchange of [14C]‐Chol from liposomes to sperm was observed (n = 4), and sperm motility was 80%. Sperm were then washed and 50 × 106 sperm were incubated as before with PC/PE liposomes containing no Chol. After 90 min, sperm were separated from liposomes by centrifugation. Measurement of [14C]‐Chol in the liposomes (supernatant) and parallel gas chromatographic analysis of extracted, saponified liposomes (n = 4) indicated that 30% of sperm Chol was removed by this procedure. Chol efflux decreased percent motile sperm by less than 10% but reduced sperm velocity by more than 50%. Sperm incubated with no liposomes (control), with liposomes containing Chol ( + Chol), and with Chol‐free liposomes (—Chol) were washed and resuspended in TS with 0.2% BSA and 30 μg lysophosphatidylcholine (LPC)/mg bovine serum albumin (BSA). Percent sperm undergoing the acrosome reaction (AR) upon incubation with LPC‐BSA was used as a measure of sperm capacitation. After 60 min of exposure to LPC‐BSA at 39°C, the mean (± SE) percent motile sperm for control, +Chol, and —Chol treatments was 57.0 ± 4.9, 60.0 ± 4.7, and 57.0 ± 6.8, respectively. Corresponding values for percent AR were 14.0 ± 3.4, 20.3 ± 4.4, and 39.7 ± 1.2. These results suggest that loss of Chol from bovine sperm may be an early step in sperm capacitation in this species.

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Wiley

Tập 20 Số 2

145-157

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