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Kinetics of rhodopsin bleaching in the isolated human retina
Author(s) -
Baumann Ch.,
Bender Silvia
Publication year - 1973
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1973.sp010415
Subject(s) - rhodopsin , opsin , retinal , absorbance , retina , chemistry , kinetics , biophysics , hydrolysis , chromatography , biochemistry , biology , optics , physics , quantum mechanics
1. Pieces of human retina were dissected from eyes enucleated because of malignant tumours. The isolated retinas were perfused by an ionic medium (36° C) and investigated spectrophotometrically. 2. Rhodopsin was identified on the basis of its difference spectrum. The maximum absorbance change on bleaching was about 0·1 (λ = 500 nm). 3. The process of bleaching was quantitatively analysed in terms of four slow reactions, viz. ( a ) conversion of metarhodopsin II into metarhodopsin III, ( b ) hydrolysis of metarhodopsin II into retinal and opsin, ( c ) decay of metarhodopsin III to retinal, and ( d ) reduction of retinal to retinol. 4. First‐order rate constants for the reactions in 3 were 9 × 10 −3 sec −1 ( a ), 3 × 10 −3 sec −1 ( b ), 4 × 10 −3 sec −1 ( c ), and 3 × 10 −2 sec −1 ( d ). 5. With two simplified versions of the model summarized in 3 and 4, the description of experimental data was less accurate.