Calcium Signaling in Xenopus oocyte

Abstract

Knowledge about calcium signaling had increased thanks to the development and manipulation of various cell models. Among all of these prototypes, Xenopus laevis oocyte appears to be one of the most relevant. The understanding of the role of calcium during oocyte oogenesis, maturation and fertilization is facilitated by the big size of the cell but also by using imaging and electrophysiological approaches. So, this chapter presents how recordings of calcium-activated chloride channels and Store-Operated Calcium Channels activities lead to demonstrate the implication of the MPF in the uncoupling between intracellular calcium releasing and capacitative calcium entry. Moreover, it will help us to understand the several reorganizations happening consequently to the pH variations of maturation or just at the moment of fertilization.

Xenopus laevis oocyte maturation is affected by metal chlorides

“…Three currents were obtained: ICl1-S, measured at the end of the first pulse at + 40 mV, ICl2, measured at the end of the À140 mV pulse and ICl1-T, calculated by measuring the peak transient current during the second pulse at + 40 mV and subtracting ICl1-S. (C) Typical recordings before (black dotted line), during (black line) and after (gray line) calcium store depletion were illustrated here. (Modified from Marin et al, 2010;Marin, 2012). 25 mg L À1 exposure, less than 40% of oocytes underwent maturation and after 12.5 mg L À1 exposures less than 60% of maturation was observed.…”

“…The morphologic events of oocyte meiotic resumption are related to ionic actors: (i) calcium channels and/or (ii) calcium-activated channels (Marin, 2012;Sun et al, 2008). That is the reason why calcium-activated chloride currents (ICl) were recorded using the triple step protocol (Fig.…”

“…laevis oocyte has been used for decades as a model for studying calcium signaling (Delisle, 1991;DeLisle and Welsh, 1992;Marin, 2012;Marin et al, 2010), cell cycle transitions (Bodart et al, 2002;Heikkila et al, 2007;Machaca, 2007). However, this model has been seldom used in toxicological studies in spite of the advantages provided by different species of Xenopus genus (Khokha, 2012;Schultz and Dawson, 2003).…”

Inhibitory actions of bisabolol on α7-nicotinic acetylcholine receptors

“…The extent of bisabolol inhibition remained unaltered in oocytes injected with BAPTA and recorded in a solution containing 2 mM Ba 2+ , suggesting that Ca 2+ -dependent Cl -channels were not involved in bisabolol inhibition of nicotinic receptors. Furthermore, since Ca 2+ -activated Cl -channels are highly sensitive to Bisabolol inhibits α7-nACh receptors 16 intracellular Ca 2+ levels (for reviews : Hartzell et al, 2005;Marin, 2012), changes in intracellular Ca 2+ levels would cause alterations in the holding current under voltage-clamp conditions.…”

“…In addition, anti-nociceptive and anti-inflammatory actions of bisabolol have been reported in recent studies (Leite et al, 2011;2012;Rocha et al, 2011a). The molecular and cellular mechanisms mediating the pharmacological action of bisabolol remain unknown.…”