Is a Ca2+ -ATPase involved in Ca2+ regulation during capacitation and the acrosome reaction of guinea-pig spermatozoa?

Abstract

Summary. The Ca2+-ATPase antagonists quercetin and ethacrynic acid accelerated the onset of the acrosome reaction in guinea-pig spermatozoa incubated in the continuous presence of Ca2+, whereas furosemide had no effect, and sodium orthovanadate only affected sperm motility. When spermatozoa were preincubated in a 'Ca2+ -free' medium, quercetin and ethacrynic acid shortened capacitation time: spermatozoa incubated for 1 h in 100\p=n-\200 \g=m\M-ethacrynic acid showed 60\p=n-\80%acrosome reactions when Ca2+ was added. Such spermatozoa were able to fertilize zona-free hamster eggs. Our results therefore point to the possible involvement of a Ca2+-ATP in the regulation of intracellular Ca2+ in spermatozoa. Cysteine and dithiothreitol, both disulphide reducing agents, prevented the effects of quercetin and ethacrynic acid, suggesting that sulphydryl groups may be important for the expression of Ca2+-ATPase activity. Lysophosphatidylserine (LS) also prevented the stimulatory effect of ethacrynic acid, an effect similar to that shown by LS on lysophosphatidylcholine (LC). It is argued that both LS and LC could exert their action through an effect on the Ca2 +-ATPase.

Localizations of intracellular calcium and Ca2+-ATPase in hamster spermatogenic cells and spermatozoa

“…However, the Ca 2þ -ATPase is weakly reacted in the PM of sperm head and outer mitochondria membrane of the middle-piece in the capacitated spermatozoa. Our observations provides direct evidence that a decrease in Ca 2þ -ATPase activity occurs during hamster sperm capacitation, enabling a rise in [Ca 2þ ] i to the threshold required for capacitation, which is a similar to previous studies showing that Ca 2þ -ATPase antagonists or inhibitors accelerated the onset of the capacitation and the acrosome reaction in human (DasGupta et al, 1994;Perry et al, 1997;Rossato et al, 2001), mouse (Fraser and McDermott, 1992;Susan et al, 1996), and guinea-pig (Li and Chen, 1996;Roldan and Fleming, 1989) spermatozoa.…”

“…A calcium-related Ca 2þ -ATPase has been identified in mammalian spermatozoa, but its significance in the regulation of intracellular calcium is the subject of considerable debate (Fraser, 1987b;Roldan and Fleming, 1989). However, incubation of guinea-pig (Roldan and Fleming, 1989) and mouse (Fraser and McDermott, 1992) spermatozoa with inhibitors of Ca 2þ -ATPase activity shortens capacitation time, indicating a possible role for Ca 2þ -ATPase in regulating capacitation (Feng, 1994;Feng et al, 1993a,b;Fraser and McDermott, 1992).…”

“…However, incubation of guinea-pig (Roldan and Fleming, 1989) and mouse (Fraser and McDermott, 1992) spermatozoa with inhibitors of Ca 2þ -ATPase activity shortens capacitation time, indicating a possible role for Ca 2þ -ATPase in regulating capacitation (Feng, 1994;Feng et al, 1993a,b;Fraser and McDermott, 1992). Despite the importance of calcium in cellular events, little is known on calcium homeostasis and the functional relationships between calcium and Ca 2þ -ATPase during spermatogenic differentiation, sperm capacitation, and acrosome reaction.…”

Voltage-dependent anion channels are a key factor of male fertility

“…In spermatozoa, extracellular Ca 2þ requires a sufficient amount of calcium because increased [Ca 2þ ] i is necessary for sperm capacitation (17,18,(54)(55)(56)(57)(58). This capacitation involves increased levels of cyclic AMP, which lead to increases in tyrosine phosphorylation, subsequently initiating the acrosome reaction and hyperactivation of sperm motility for fertilization by protein kinase A (59)(60)(61)(62) ] i was not decreased after capacitation in spermatozoa treated with DIDS, as VDACs affects Ca 2þ penetration to the outer membrane of spermatozoa for capacitation and the acrosome reaction.…”

Ca2+‐Regulating mechanisms that modulate bull sperm capacitation and acrosomal exocytosis as determined by chlortetracycline analysis

“…In somatic cells, a Ca2'-ATPase located in the plasma membrane maintains low [Ca2+], by pumping Ca2+ out of the cell (Schatzmann, 1982), and such an enzyme has been identified in mammalian sperm (reviewed by Fraser, 1987a). Recent studies on guinea pig (Roldan and Fleming, 1989), human (DasGupta et al, 1994), and mouse sperm (Fraser and McDermott, 1992;Adeoya-Osiguwa and Fraser, 1993) have provided indirect evidence that such an ATPase may play a role during capacitation. Treatment with compounds capable of interfering either directly or indirectly with Ca2+-ATPase activity, and thus allowing [Ca2+], to rise, accelerated capacitation.…”