Reduction of the fertilizing capacity of sea urchin sperm by cannabinoids derived from marihuana. I. Inhibition of the acrosome reaction induced by egg jelly

1991 ◽  
Vol 29 (1) ◽  
pp. 51-59 ◽  
Author(s):  
Herbert Schuel ◽  
Diana Berkery ◽  
Regina Schuel ◽  
Michael C. Chang ◽  
Arthur M. Zimmerman ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Acrosome Reaction ◽  
Egg Jelly ◽  
Sea Urchin Sperm

scholarly journals Ca2+ channels from the sea urchin sperm plasma membrane.

1990 ◽  
Vol 95 (2) ◽  
pp. 273-296 ◽  
Author(s):  
A Liévano ◽  
E C Vega-SaenzdeMiera ◽  
A Darszon
Keyword(s):  
Plasma Membrane ◽  
Sea Urchin ◽  
Acrosome Reaction ◽  
Main Channel ◽  
Open Probability ◽  
Boltzmann Function ◽  
Sperm Plasma Membrane ◽  
Egg Jelly ◽  
Sea Urchin Sperm ◽  
Ca2 Channels

Ca2+ influx across the sea urchin sperm plasma membrane is a necessary step during the egg jelly-induced acrosome reaction. There is pharmacological evidence for the involvement of Ca2+ channels in this influx, but their presence has not been directly demonstrated because of the small size of this cell. Sea urchin sperm Ca2+ channels are being studied by fusing isolated plasma membranes into planar lipid bilayers. With this strategy, a Ca2+ channel has been detected with the following characteristics: (a) the channel exhibits a high mainstate conductance (gamma MS) of 172 pS in 50 mM CaCl2 solutions with voltage-dependent decaying to smaller conductance states at negative Em; (b) the channel is blocked by millimolar concentrations of Cd2+, Co2+, and La3+, which also inhibit the egg jelly-induced acrosome reaction; (c) the gamma MS conductance sequence for the tested divalent cations is the following: Ba2+ greater than Sr2+ greater than Ca2+; and (d) the channel discriminates poorly for divalent over monovalent cations (PCa/PNa = 5.9). The sperm Ca2+ channel gamma MS rectifies in symmetrical 10 mM CaCl2, having a maximal slope conductance value of 94 pS at +100 mV applied to the cis side of the bilayer. Under these conditions, a different single-channel activity of lesser conductance became apparent above the gamma MS current at positive membrane potentials. Also in 10 mM Ca2+ solutions, Mg2+ permeates through the main channel when added to the cis side with a PCa/PMg = 2.9, while it blocks when added to the trans side. In 50 mM Ca2+ solutions, the gamma MS open probability has values of 1.0 at voltages more positive than -40 mV and decreases at more negatives potentials, following a Boltzmann function with an E0.5 = -72 mV and an apparent gating charge value of 3.9. These results describe a novel Ca2(+)-selective channel, and suggest that the main channel works as a single multipore assembly.

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