Voltage sensitivity of the osteoclast calcium receptor.
We demonstrated previously that osteoclasts possess a divalent cation-sensitive "receptor", the Ca2+ receptor. Activation of the Ca2+ receptor by the surrogate cation Ni2+ was shown to elicit an increase in cytosolic [Ca2+] to a peak value followed by an exponential decline. In the present study we examined the influence of surface membrane voltage on the kinetics of Ca2+ receptor inactivation. The K+ ionophore, valinomycin was applied to intercept the declining phase of the cytosolic [Ca2+] transient elicited by application of between 50 microM- and 5 mM-[Ni2+]. This resulted in a sustained elevation of cytosolic [Ca2+] or even a 'hump' followed by a gradual decline. Such a kinetic alteration persisted in a Ca(2+)-free solution, but was abolished in high extracellular [K+] (105 mM). Thus, we demonstrate for the first time to our knowledge, a modulatory effect of membrane potential on the function of the osteoclast Ca2+ receptor.
Bone Research Unit, St. George's Hospital Medical School, London, U.K.
M
M
Pazianas
M
M
Zaidi
C L
CL
Huang
B S
BS
Moonga
V S
VS
Shankar
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D016257:Fura-2; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D010010:Osteoclasts / Q000378:metabolism / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014634:Valinomycin / Q000494:pharmacology
D002135:Calcium-Binding Proteins; D014634:Valinomycin; D011188:Potassium; D002118:Calcium; D016257:Fura-2