Effect of pentachlorophenol on calcium accumulation in barnacle muscle cells.
1. The effect of extracellularly applied pentachlorophenol (PCP) was studied on the membrane potential (Vm) and Ca2+ uptake in isolated single skeletal muscle cells of Balanus nubilus. 2. When compared with the controls, 0.1 mM PCP induced a significant (P < 0.05) increase in Ca2+ uptake accompanied by membrane depolarization (9 mV at 45 min incubation). This depolarization was reduced by 11% of extracellular Ca2+ (Cao2+) was replaced by Tris+ and by 50% if extracellular Na+ was also replaced by Tris+. 3. The Ca2+ channel blocker, verapamil (0.1 mM), completely inhibited the PCP-induced Ca2+ uptake as well as the membrane depolarization either in the absence or presence of Cao2+. Experiments on voltage-clamped cells show that the PCP-induced Ca2+ uptake was independent of the PCP-induced depolarization. 4. The results indicate that PCP induces activation of a verapamil-sensitive Ca2+ influx pathway (presumably L-type Ca2+ channels) independent of Vm. The permeation of Ca2+, Na+ and Tris+ through this pathway produces membrane depolarization in the following order of effectiveness: Ca2+ > Na+ > Tris+.
Nwoga
J C
JC
Department of Biology, Florida A & M University, Tallahassee 32307, USA.
Sniffen
J C
JC
Peña-Rasgado
C
C
Kimler
V A
VA
Rasgado-Flores
H
H
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002132:Calcium Radioisotopes; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010416:Pentachlorophenol / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism; D001468:Thoracica / Q000378:metabolism*; D014325:Tromethamine; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D002132:Calcium Radioisotopes; D014325:Tromethamine; D012964:Sodium; D014700:Verapamil; D010416:Pentachlorophenol; D002118:Calcium