The stable products of the non-enzymatic glycation of pig crystallins: new findings related to the pathogenesis of diabetic cataracts.
The incorporation of 14C-glucose in native pig lens crystallins by in vitro incubation was found, after subsequent dialysis, to affect all five classes of crystallin separated by Sepharose CL-6B chromatography, but four times more radioactivity appeared in the alpha-H fraction than in any of the others (14.25 vs 3.16, 3.25, 1.69 and 2.30 kCPM/mg for alpha-H, alpha-L, beta-H, beta-L and gamma crystallins respectively). The autoradiographs of one- and two-dimensional electrophoresis patterns nevertheless showed the total radioactivity to be quite evenly distributed among the various subunits of the proteins; the alpha-H subunits did not exhibit a markedly greater affinity for glucose than the others. The high levels of stable glycation products in the alpha-H fraction are therefore attributed to the fraction's increasing during glycation rather than to its components being especially susceptible to glycation. This finding is interpreted as supporting the glycation-originated protein hyper-aggregation theory of the pathogenesis of diabetic cataract.
Vidal
P
P
Service of Endocrinology and Nutrition, Hospital General de Galicia, University of Santiago de Compostela, Spain.
Cabezas-Cerrato
J
J
D000818:Animals; D001345:Autoradiography; D002250:Carbon Radioisotopes; D002386:Cataract / Q000209:etiology*; D003459:Crystallins / Q000302:isolation & purification / Q000378:metabolism*; D003930:Diabetic Retinopathy / Q000209:etiology*; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D005947:Glucose / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D008954:Models, Biological; D013552:Swine
D002250:Carbon Radioisotopes; D003459:Crystallins; D005947:Glucose