Differential sensitivity to calciseptine of L-type Ca(2+) currents in a 'lower' vertebrate (Scyliorhinus canicula), a protochordate (Branchiostoma lanceolatum) and an invertebrate (Alloteuthis subulata).
Voltage-dependent calcium currents in vertebrate (Scyliorhinus canicula), protochordate (Branchiostoma lanceolatum), and invertebrate (Alloteuthis subulata) skeletal and striated muscle were examined under whole-cell voltage clamp. Nifedipine (10 microM) suppressed and cobalt (5 mM) blocked striated/skeletal muscle calcium currents in all of the animals examined, confirming that they are of the L-type class. Calciseptine, a specific blocker of vertebrate cardiac muscle and neuronal L-type calcium currents, was applied (0.2 microM) under whole-cell voltage clamp. Protochordate and invertebrate striated muscle L-type calcium currents were suppressed while up to 4 microM calciseptine had no effect on dogfish skeletal muscle L-type calcium currents. Our results demonstrate the presence of at least two sub-types of L-type calcium current in these different animals, which may be distinguished by their calciseptine sensitivity. We conclude that the invertebrate and protochordate L-type current sub-type that we have examined has properties in common with vertebrate 'cardiac' and 'neuronal' current sub-types, but not the skeletal muscle sub-type of the L-type channel.
Rogers
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CM
The Marine Biological Association of the UK, Citadel Hill, Plymouth PL1 2PB, UK. cmr@soton.ac.uk
Brown
E R
ER
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000145:classification / Q000187:drug effects* / Q000502:physiology*; D002816:Chordata, Nonvertebrate / Q000502:physiology*; D003035:Cobalt / Q000494:pharmacology; D049832:Decapodiformes / Q000502:physiology*; D004284:Dogfish / Q000502:physiology*; D004351:Drug Resistance; D004546:Elapid Venoms / Q000494:pharmacology*; D004553:Electric Conductivity; D066298:In Vitro Techniques; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D004546:Elapid Venoms; D003035:Cobalt; C067971:calciseptine; D009543:Nifedipine