Calcium-activated calcium permeability in parathyroid cells.
The Ca2+ receptor mechanism of the parathyroid cell was studied using La3+ as a probe. La3+ was found to bind to the cell surface without further penetration. Measurements of 45Ca fluxes and the cytoplasmic Ca2+ concentration (Ca2+i) revealed a stimulatory component in the action of La3+ on Ca2+ permeability resulting in a rise in Ca2+i. These effects mimicked those obtained when raising the extracellular Ca2+ concentration from 0.5 to 3.0 mM, but the actions of La3+ and Ca2+ were not additive. The results suggest the existence of a novel Ca2+ permeability physiologically activated by binding of Ca2+ to an external receptor.
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D007811:Lanthanum / Q000494:pharmacology; D010280:Parathyroid Glands / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D007473:Ion Channels; D007811:Lanthanum; D002118:Calcium