Silent Calcium Channels in Skeletal Muscle Fibers of the Crustacean Atya lanipes

Silent Calcium Channels in Skeletal Muscle Fibers of the Crustacean Atya lanipes The superficial (tonic) abdominal flexor muscles of Atya lanipes do not generate Ca2+ action potentials when depolarized and have no detectable inward Ca2+ current. These fibers, however, are strictly dependent on Ca2+ influx for contraction, suggesting that they depend on Ca2+-induced Ca2+ release for contractile activation. The nature of the communication between Ca2+ channels in the sarcolemmal/tubular membrane and Ca2+ release channels in the sarcoplasmic reticulum in this crustacean muscle was investigated. The effects of dihydropyridines on tension generation and the passive electrical response were examined in current-clamped fibers: Bay K 8644 enhanced tension about 100% but did not alter the passive electrical response; nifedipine inhibited tension by about 70%. Sr2+ and Ba2+ action potentials could be elicited in Ca2+-free solutions. The spikes generated by these divalent cations were abolished by nifedipine. As the Sr2+ or Ba2+ concentrations were increased, the amplitudes of the action potentials and their maximum rate of rise, V max , increased and tended towards saturation. Three-microelectrode voltage-clamp experiments showed that even at high (138 mm) extracellular Ca2+ concentration the channels were silent, i.e., no inward Ca2+ current was detected. In Ca2+-free solutions, inward currents carried by 138 mm Sr2+ or Ba2+ were observed. The currents activated at voltages above −40 mV and peaked at about 0 mV. This voltage-activation profile and the sensitivity of the channels to dihydropyridines indicate that they resemble L-type Ca2+ channels. Peak inward current density values were low, ca.−33 μA/cm2 for Sr2+ and −14 μA/cm2 for Ba2+, suggesting that Ca2+ channels are present at a very low density. It is concluded that Ca2+-induced Ca2+ release in this crustacean muscle operates with an unusually high gain: Ca2+ influx through the silent Ca2+ channels is too low to generate a macroscopic inward current, but increases sufficiently the local concentration of Ca2+ in the immediate vicinity of the sarcoplasmic reticulum Ca2+ release channels to trigger the highly amplified release of Ca2+ required for tension generation. The Journal of Membrane Biology Springer Journals

Silent Calcium Channels in Skeletal Muscle Fibers of the Crustacean Atya lanipes

Loading next page...
Copyright © Inc. by 2000 Springer-Verlag New York
Life Sciences; Biochemistry, general; Human Physiology
Publisher site
See Article on Publisher Site

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.

DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 12 million articles from more than
10,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Unlimited reading

Read as many articles as you need. Full articles with original layout, charts and figures. Read online, from anywhere.

Stay up to date

Keep up with your field with Personalized Recommendations and Follow Journals to get automatic updates.

Organize your research

It’s easy to organize your research with our built-in tools.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

Monthly Plan

  • Read unlimited articles
  • Personalized recommendations
  • No expiration
  • Print 20 pages per month
  • 20% off on PDF purchases
  • Organize your research
  • Get updates on your journals and topic searches


Start Free Trial

14-day Free Trial

Best Deal — 39% off

Annual Plan

  • All the features of the Professional Plan, but for 39% off!
  • Billed annually
  • No expiration
  • For the normal price of 10 articles elsewhere, you get one full year of unlimited access to articles.



billed annually
Start Free Trial

14-day Free Trial