title: The calcium feedback signal in the phototransduction cascade of vertebrate rods.
abstract: Intracellular free Ca (Cai) was measured in functionally intact rod outer segments in darkness and during light responses using the fluorescent Ca indicator Indo-dextran. In darkness, Cai was 554 +/- 25 nM (n = 28) for -85 +/- 2 pA of circulating dark current (Id) and declined in saturating light to a minimum value of approximately 50 nM with a time course that paralleled the fall in Na:Ca,K exchange current. During a subsaturating flash response that reduced Id by 70%, Cai fell to a minimum of approximately 325 nM and recovered incompletely to a plateau of approximately 450 nM that lasted approximately 15 s after full recovery of Id. During a 60 s step that caused approximately 7-fold reduction in sensitivity of superimposed flash responses, Cai reached a steady-state level of approximately 252 nM.
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle 98195.
authors.forename: M P
authors.initials: MP
authors.lastname: Gray-Keller
authors.forename: P B
authors.initials: PB
authors.lastname: Detwiler
mesh_terms: D000221:Adaptation, Ocular; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003624:Darkness; D003911:Dextrans / Q000378:metabolism; D004553:Electric Conductivity; D005246:Feedback; D005456:Fluorescent Dyes; D007211:Indoles / Q000378:metabolism; D007700:Kinetics; D008027:Light; D008116:Lizards; D010777:Photochemistry; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D003911:Dextrans; D005456:Fluorescent Dyes; D007211:Indoles; C048960:indo-1; D002118:Calcium