Light-dependent Na(+)-Ca2+ exchange in retinal rod discs.
Experiments are described demonstrating that Na(+)-Ca2+ exchange of retinal rod disc membrane is highly sensitive to light. The Na(+)-Ca2+ exchanger was shown to possess two types of binding sites with different affinities for calcium. The low affinity binding sites (KCaD = 5.8 mumol/l) are light-insensitive. After bleaching, KD of the high affinity Ca2(+)-binding sites an Ki for Na+ changed from 0.2 to 0.3 mumol/l and from 3.2 to 0.7 nmol/l, respectively. Light inhibits the steady-state Ca2+ uptake by a factor of 1.5. Photocontrol of the Na(+)-Ca2+ exchanger affinity is observed at the physiological level of rhodopsin bleaching.
Volotovski
I D
ID
Institute of Photobiology, Academy of Sciences of the BSSR, Minsk, USSR.
Khovratovich
V I
VI
Orlov
S N
SN
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D006152:Cyclic GMP / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008027:Light; D008985:Monensin / Q000494:pharmacology; D010786:Photoreceptor Cells / Q000378:metabolism*; D011802:Quinidine / Q000494:pharmacology; D012243:Rhodopsin / Q000378:metabolism / Q000528:radiation effects; D012374:Rod Cell Outer Segment / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D012430:Ruthenium Red / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*
D012430:Ruthenium Red; D000001:Calcimycin; D012243:Rhodopsin; D008985:Monensin; D012964:Sodium; D006152:Cyclic GMP; D011802:Quinidine; D002118:Calcium