INVITRO GLYCATION AND ACETYLATION (BY ASPIRIN) OF RAT CRYSTALLINS

In vitro studies with rat lens crystallins were conducted to explore t he mechanism by which aspirin (ASA-acetylsalicylic acid) could inhibit cataractogenesis. The purpose of the present study is to show whether gamma-crystallin is the primary target for glycation by glucose and a cetylation by ASA. Lens soluble fractions from one and seven month old Sprague-Dawley rats were incubated with 5 mM [C-14]glucose with and w ithout 10 mM ASA. alpha, beta, and gamma-crystallins were separated by molecular sieve HPLC and specific activities of each crystallin deter mined. In vitro acetylation was also studied by measuring protein boun d [C-14]acetyl groups after incubation with [C-14]acetyl ASA. There wa s 2 to 4-fold faster glycation of gamma-crystallin than all other crys tallins from 1-month-old rats and ASA inhibited glycation of gamma-cry stallin four times more than that of alpha and beta-crystallins,thus s howing preferential glycation of gamma-crystallin and its selective in hibition by ASA. [C-14]acetyl incorporation showed increased acetylati on of gamma-crystallin in one month old rats, whereas in older lenses acetylation of other crystallins predominated. Treatment with 10 mM AS A showed 35% decrease in free -NH2 groups but protein thiols remained unchanged.