Bicarbonate and bovine serum albumin reversibly 'switch' capacitation-induced events in human spermatozoa

TY - JOUR

T1 - Bicarbonate and bovine serum albumin reversibly 'switch' capacitation-induced events in human spermatozoa

AU - Bedu-Addo, K

AU - Lefièvre, L

AU - Moseley, F L C

AU - Barratt, C L R

AU - Publicover, S J

PY - 2005/9/28

Y1 - 2005/9/28

N2 - We have investigated the reversibility of biochemical and physiological changes that occur upon suspension of ejaculated human spermatozoa during in vitro capacitation. Cells were swum up in a simple HEPES-based saline [lacking bicarbonate and bovine serum albumin (BSA)], then resuspended either in supplemented Earle's balanced salt solution (sEBSS) (25 mM bicarbonate) with 0.3% BSA (for in vitro capacitation) or in medium-lacking bicarbonate and/or BSA. Progesterone-induced acrosome reaction (AR) developed during in vitro capacitation (6 h). A progesterone-induced [Ca2+]i signal was detectable in cells maintained in the simple HEPES-based saline, but upon transfer to sEBSS, the response increased three- to four-fold, saturating within <30 min. Serine/threonine phosphorylation saturated within minutes of resuspension, but tyrosine phosphorylation developed over 3 h. Return of cells to non-capacitating conditions caused reversal of all capacitation-dependent changes. The [Ca2+]i signal reverted to its 'uncapacitated' size within <30 min. Protein phosphorylation reversed gradually and could be reinduced (kinetics resembling the first response) upon resuspension in sEBSS. The ability of cells to undergo progesterone-induced AR fell to levels similar to those in uncapacitated cells within 1 h of resuspension in medium not supporting capacitation. Loss of protein phosphorylation occurred only in the absence of both bicarbonate and BSA, but effects on [Ca2+]i signalling and AR could be seen after removal of only one of these factors. We conclude that key events in the capacitation of human spermatozoa are both reversible and repeatable.

AB - We have investigated the reversibility of biochemical and physiological changes that occur upon suspension of ejaculated human spermatozoa during in vitro capacitation. Cells were swum up in a simple HEPES-based saline [lacking bicarbonate and bovine serum albumin (BSA)], then resuspended either in supplemented Earle's balanced salt solution (sEBSS) (25 mM bicarbonate) with 0.3% BSA (for in vitro capacitation) or in medium-lacking bicarbonate and/or BSA. Progesterone-induced acrosome reaction (AR) developed during in vitro capacitation (6 h). A progesterone-induced [Ca2+]i signal was detectable in cells maintained in the simple HEPES-based saline, but upon transfer to sEBSS, the response increased three- to four-fold, saturating within <30 min. Serine/threonine phosphorylation saturated within minutes of resuspension, but tyrosine phosphorylation developed over 3 h. Return of cells to non-capacitating conditions caused reversal of all capacitation-dependent changes. The [Ca2+]i signal reverted to its 'uncapacitated' size within <30 min. Protein phosphorylation reversed gradually and could be reinduced (kinetics resembling the first response) upon resuspension in sEBSS. The ability of cells to undergo progesterone-induced AR fell to levels similar to those in uncapacitated cells within 1 h of resuspension in medium not supporting capacitation. Loss of protein phosphorylation occurred only in the absence of both bicarbonate and BSA, but effects on [Ca2+]i signalling and AR could be seen after removal of only one of these factors. We conclude that key events in the capacitation of human spermatozoa are both reversible and repeatable.

KW - Acrosome Reaction

KW - Bicarbonates/pharmacology

KW - Calcium Signaling

KW - Cells, Cultured

KW - Culture Media

KW - Humans

KW - Male

KW - Phosphorylation

KW - Progesterone

KW - Protein-Serine-Threonine Kinases/metabolism

KW - Protein-Tyrosine Kinases/metabolism

KW - Serum Albumin, Bovine/pharmacology

KW - Sodium Bicarbonate/pharmacology

KW - Sperm Capacitation

KW - Spermatozoa/drug effects

U2 - 10.1093/molehr/gah226

DO - 10.1093/molehr/gah226

M3 - Article

C2 - 16192296

SN - 1360-9947

VL - 11

SP - 683

EP - 691

JO - Molecular Human Reproduction

JF - Molecular Human Reproduction

IS - 9

ER -