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Speract induces calcium oscillations in the sperm tail.

Wood CD, Darszon A, Whitaker M - J. Cell Biol. (2003)

Bottom Line: These data point to a model in which a messenger generated periodically in the tail diffuses to the head.Sperm are highly polarized cells.Our results indicate that a clear understanding of the link between [Ca2+]i and sperm motility will only be gained by analysis of [Ca2+]i signals at the level of the single sperm.

View Article: PubMed Central - PubMed

Affiliation: School of Cell and Molecular Biosciences, University of Newcastle upon Tyne, NE2 4HH, UK.

ABSTRACT
Sea urchin sperm motility is modulated by sperm-activating peptides. One such peptide, speract, induces changes in intracellular free calcium concentration ([Ca2+]i). High resolution imaging of single sperm reveals that speract-induced changes in [Ca2+]i have a complex spatiotemporal structure. [Ca2+]i increases arise in the tail as periodic oscillations; [Ca2+]i increases in the sperm head lag those in the tail and appear to result from the summation of the tail signal transduction events. The period depends on speract concentration. Infrequent spontaneous [Ca2+]i transients were also seen in the tail of unstimulated sperm, again with the head lagging the tail. Speract-induced fluctuations were sensitive to membrane potential and calcium channel blockers, and were potentiated by niflumic acid, an anion channel blocker. 3-isobutyl-1-methylxanthine, which potentiates the cGMP/cAMP-signaling pathways, abolished the [Ca2+]i fluctuations in the tail, leading to a very delayed and sustained [Ca2+]i increase in the head. These data point to a model in which a messenger generated periodically in the tail diffuses to the head. Sperm are highly polarized cells. Our results indicate that a clear understanding of the link between [Ca2+]i and sperm motility will only be gained by analysis of [Ca2+]i signals at the level of the single sperm.

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Representative examples of the effect of Ni2+ treatment on speract-induced [Ca2+]i increases in individual sperm heads. Blue traces from sperm treated with 300 μM Ni2+ before addition of 500 pM speract (indicated by arrow); red trace from untreated sperm. Changes in [Ca2+]i were determined for individual heads by ratioing their fluorescence (F) against their initial fluorescence (F0). Images acquired at 10 frames per second with 100-ms individual frame exposure time.
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fig7: Representative examples of the effect of Ni2+ treatment on speract-induced [Ca2+]i increases in individual sperm heads. Blue traces from sperm treated with 300 μM Ni2+ before addition of 500 pM speract (indicated by arrow); red trace from untreated sperm. Changes in [Ca2+]i were determined for individual heads by ratioing their fluorescence (F) against their initial fluorescence (F0). Images acquired at 10 frames per second with 100-ms individual frame exposure time.

Mentions: To initiate the study of the ion transport systems involved in the [Ca2+]i fluctuations, we tested blockers of VDCC and inhibitors of anion channels. Fig. 7 depicts the effect of 300 μM Ni2+, a blocker of VDCC that is more potent for T-type Ca2+ channels and also blocks a second poorly characterized Ca2+ channel involved in the sea urchin sperm AR (González-Martinez et al., 2001). Ni2+ at this concentration only mildly affects the tonic response, but significantly inhibits the speract-induced fluctuations in [Ca2+]i (n = 28). 300 μM Cd2+, which is a better blocker of L-type VDCC, was ineffective (unpublished data). Together, these data indicate that a channel with similar properties as T-type Ca2+ channel may be involved in generating the speract-induced [Ca2+]i fluctuations. Consistent with this idea, nimodipine, a Ca2+-channel blocker that at 10 μM can block T-type VDCC in mouse spermatogenic cells (Arnoult et al., 1997), also affected the speract-induced fluctuations (unpublished data). However, these findings do not rule out that other Ca2+-permeable channels (e.g., the second, Ni2+-sensitive channel involved in the AR; González-Martinez et al., 2001) may participate in the speract-induced [Ca2+]i fluctuations.


Speract induces calcium oscillations in the sperm tail.

Wood CD, Darszon A, Whitaker M - J. Cell Biol. (2003)

Representative examples of the effect of Ni2+ treatment on speract-induced [Ca2+]i increases in individual sperm heads. Blue traces from sperm treated with 300 μM Ni2+ before addition of 500 pM speract (indicated by arrow); red trace from untreated sperm. Changes in [Ca2+]i were determined for individual heads by ratioing their fluorescence (F) against their initial fluorescence (F0). Images acquired at 10 frames per second with 100-ms individual frame exposure time.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172867&req=5

fig7: Representative examples of the effect of Ni2+ treatment on speract-induced [Ca2+]i increases in individual sperm heads. Blue traces from sperm treated with 300 μM Ni2+ before addition of 500 pM speract (indicated by arrow); red trace from untreated sperm. Changes in [Ca2+]i were determined for individual heads by ratioing their fluorescence (F) against their initial fluorescence (F0). Images acquired at 10 frames per second with 100-ms individual frame exposure time.
Mentions: To initiate the study of the ion transport systems involved in the [Ca2+]i fluctuations, we tested blockers of VDCC and inhibitors of anion channels. Fig. 7 depicts the effect of 300 μM Ni2+, a blocker of VDCC that is more potent for T-type Ca2+ channels and also blocks a second poorly characterized Ca2+ channel involved in the sea urchin sperm AR (González-Martinez et al., 2001). Ni2+ at this concentration only mildly affects the tonic response, but significantly inhibits the speract-induced fluctuations in [Ca2+]i (n = 28). 300 μM Cd2+, which is a better blocker of L-type VDCC, was ineffective (unpublished data). Together, these data indicate that a channel with similar properties as T-type Ca2+ channel may be involved in generating the speract-induced [Ca2+]i fluctuations. Consistent with this idea, nimodipine, a Ca2+-channel blocker that at 10 μM can block T-type VDCC in mouse spermatogenic cells (Arnoult et al., 1997), also affected the speract-induced fluctuations (unpublished data). However, these findings do not rule out that other Ca2+-permeable channels (e.g., the second, Ni2+-sensitive channel involved in the AR; González-Martinez et al., 2001) may participate in the speract-induced [Ca2+]i fluctuations.

Bottom Line: These data point to a model in which a messenger generated periodically in the tail diffuses to the head.Sperm are highly polarized cells.Our results indicate that a clear understanding of the link between [Ca2+]i and sperm motility will only be gained by analysis of [Ca2+]i signals at the level of the single sperm.

View Article: PubMed Central - PubMed

Affiliation: School of Cell and Molecular Biosciences, University of Newcastle upon Tyne, NE2 4HH, UK.

ABSTRACT
Sea urchin sperm motility is modulated by sperm-activating peptides. One such peptide, speract, induces changes in intracellular free calcium concentration ([Ca2+]i). High resolution imaging of single sperm reveals that speract-induced changes in [Ca2+]i have a complex spatiotemporal structure. [Ca2+]i increases arise in the tail as periodic oscillations; [Ca2+]i increases in the sperm head lag those in the tail and appear to result from the summation of the tail signal transduction events. The period depends on speract concentration. Infrequent spontaneous [Ca2+]i transients were also seen in the tail of unstimulated sperm, again with the head lagging the tail. Speract-induced fluctuations were sensitive to membrane potential and calcium channel blockers, and were potentiated by niflumic acid, an anion channel blocker. 3-isobutyl-1-methylxanthine, which potentiates the cGMP/cAMP-signaling pathways, abolished the [Ca2+]i fluctuations in the tail, leading to a very delayed and sustained [Ca2+]i increase in the head. These data point to a model in which a messenger generated periodically in the tail diffuses to the head. Sperm are highly polarized cells. Our results indicate that a clear understanding of the link between [Ca2+]i and sperm motility will only be gained by analysis of [Ca2+]i signals at the level of the single sperm.

Show MeSH
Related in: MedlinePlus