TAURINE DEPLETION INCREASES PHOSPHORYLATION OF A SPECIFIC PROTEIN IN THE RAT RETINA

Partial depletion of the taurine content in the rat retina was accompl ished for up to 22 weeks by introduction of 1.5% guanidino-ethanesulfo nate (GES) in the drinking water. Taurine levels decreased by 50% afte r 1 week of GES treatment and by 80% at 16 weeks. Replacement of GES b y taurine to the GES-treated rats from week 16 to 22 returned their ta urine content to the control value. Whereas addition of taurine (1.5%) to the drinking water of control rats from week 16 to 22 elevated the retinal taurine content to 118% of the control value, the administrat ion of untreated water to GES-treated animals for the 16 to 22 week ti me period increased the retinal taurine content to only 76% of the con trol value. The amplitude of the electroretinogram (ERG) b-wave was de creased by 60% after GES-treatment for 16 weeks and maintained this re duced level for up to 22 weeks. Administration of taurine in the drink ing water from week 16 to 22 returned the b-wave amplitude to a range not statistically different from the control values whereas the admini stration of untreated water produced less improvement. After 6 weeks o f GES treatment when the retinal taurine content was reduced by 70% an d the amplitude of the b-wave was reduced by 50% (extrapolated from Fi gure 1), phosphorylation of a specific protein with an approximate mol ecular weight of 20K was increased by 94%. The increased phosphorylati on of the similar to 20K protein observed after GES treatment was reve rsed when the animals were treated with taurine (1 1/2%) in the drinki ng water for an additional 6 weeks. There was no change in the phospho rylation of the similar to 20K protein when animals were treated with taurine for 6 weeks. The data obtained support the theory that taurine may have a regulatory effect on retinal protein phosphorylation.