Membrane hyperpolarization by sperm-activating and -attracting factor increases cAMP level and activates sperm motility in the ascidian Ciona intestinalis

Hiroko Izumi, T. Márián, Kazuo Inaba, Yoshitaka Oka, Masaaki Morisawa

Research output: Contribution to journalArticle

50 Citations (Scopus)

Abstract

In the ascidian Ciona intestinalis (and C. savignyi), sperm-activating and -attracting factor (SAAF) is released from the egg at fertilization and stimulates both Ca2+ influx and a transient increase in cAMP level of the sperm, leading to the activation of sperm motility (M. Yoshida et al., 1994, Dev. Growth Differ. 36, 589-595). In this paper we show in C. intestinalis that valinomycin, a potassium-selective ionophore, as well as SAAF, activated sperm motility, and this activation was suppressed by extracellular high K+. Membrane potential measurements showed that both SAAF and valinomycin increase K+ permeability of sperm and induce membrane hyperpolarization, the amplitude of which depends on the external K+ concentration. The membrane potential and intracellular K+ concentration of Ciona sperm without SAAF were estimated to be about -50 mV and 560 ± 40 mM, respectively. After treatment with SAAF or valinomycin the membrane potential became almost equal to the equilibrium potential of K+ (-100 mV), and the cAMP level increased in artificial seawater. A potent voltage-dependent K+ channel blocker, MCD peptide, at the concentration of 10 μM blocked SAAF-induced hyperpolarization of the cells, increase in cAMP, and sperm motility. These results suggest that membrane hyperpolarization produced by the opening of K+ channels elevates cAMP synthesis and leads to the activation of sperm motility in Ciona.

Original languageEnglish
Pages (from-to)246-256
Number of pages11
JournalDevelopmental Biology
Volume213
Issue number2
DOIs
Publication statusPublished - Sep 15 1999

Fingerprint

Ciona intestinalis
Urochordata
Sperm Motility
Spermatozoa
Membranes
Valinomycin
Membrane Potentials
Potassium Ionophores
Seawater
Fertilization
Ovum
Permeability

Keywords

  • Adenylyl cyclase
  • Ascidian
  • Membrane hyperpolarization
  • Potassium efflux
  • Sperm motility

ASJC Scopus subject areas

  • Developmental Biology

Cite this

Membrane hyperpolarization by sperm-activating and -attracting factor increases cAMP level and activates sperm motility in the ascidian Ciona intestinalis. / Izumi, Hiroko; Márián, T.; Inaba, Kazuo; Oka, Yoshitaka; Morisawa, Masaaki.

In: Developmental Biology, Vol. 213, No. 2, 15.09.1999, p. 246-256.

Research output: Contribution to journalArticle

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