Bicarbonate: Carbon-Dioxide Regulation of Sperm Capacitation, Hyperactivated Motility, and Acrosome Reactions1

Abstract

The bicarbonate: CO2 (HCO3-:CO2) concentration dependencies of hamster sperm motility, spontaneous acrosome reactions, and zona penetration (used to assay the zona-induced acrosome reaction) were examined. A cross-over experimental design was used to segregate effects on early stages of capacitation, spanning the first 5 h of incubation, from those on acrosome reactions and zona penetration during the last 1 h. After 5 h, HCO3-:CO2 concentrations were increased, decreased, or kept the same for 1 h. Compared to no HCO3-:CO2, as little as 2.9 mM: 0.6% HCO3-:CO2 increased the sperm motility index (MI) by 2.7-3.6 times. When HCO3-:CO2 was continuously present, both progressive and hyperactivated motility were stimulated by HCO3-:CO2 in a dose-dependent manner by 3-4 h, well before completion of capacitation. Stimulation of acrosome reactions or zona penetration, by addition of HCO3-:CO2 to sperm for 1 h late in capacitation, depended mainly on levels of HCO3-:CO2 present earlier in capacitation. When 25 mM: 5% HCO3-:CO2 was added only at 5 h, responses were significantly lower than with sperm treated continuously with the same concentration of HCO3-:CO2, being 2.5 times lower for MI, 2 times lower for acrosome reactions, and 6.3 times lower for zona penetration. In contrast, decreasing HCO3-:CO2 to suboptimal levels after 5 h did not decrease any 6-h sperm responses significantly. The average maximal and one-half maximal preincubation HCO3- concentrations for all responses were 34.2 +/- 1.0 and 9.2 +/- 0.3 mM, respectively. Zona penetration and hyperactivation were highly correlated.(ABSTRACT TRUNCATED AT 250 WORDS)

A polycystin-1 controls postcopulatory reproductive selection in mice

“…It is not known whether these functional changes were regulated coordinately or independently. Previously, media conditions or pharmacological treatments dissected the development of hyperactivated sperm motility in vitro from such component events of capacitation as the increased frequency of spontaneous (that is, ZP agonistindependent) acrosome reaction (43,44) or the enhanced tyrosine protein phosphorylation that accompanies capacitation (45,46). Similarly, hyperactivation depends on the function of the Catsper family of cation channels and of Pcma4, the Ca 2ϩ -conducting ATPase (47)(48)(49).…”

Moving to the beat: a review of mammalian sperm motility regulation

“…In addition, hyperactivated motility may help the sperm to penetrate the egg vestments (Suarez et al 1991;Stauss et al 1995;Ho and Suarez 2001). In rodents, and probably in other species, hyperactivated sperm motility is also correlated with the ability of a sperm to fertilise an oocyte in vitro (Fraser and Quinn 1981;Boatman and Robbins 1991). Thus, the bulk of evidence suggests that a normal sperm must be able to acquire both activated motility in the caudal female reproductive tract and uterus and hyperactivated motility in the oviduct for it to have a reasonable chance of fertilising the egg.…”

Dynamics of flagellar force generated by a hyperactivated spermatozoon

“…It is well known that the characteristic movement of the hyperactivated spermatozoa is effective for sperm penetration through the zona pellucida (Boatman & Robbins 1991, Yanagimachi 1994. This effect has been ascribed to the large thrust (the propulsive force) generated by the hyperactivated spermatozoon (Drobnis et al 1988, Yanagimachi 1994.…”